Guidance on the design selection installation and use of IMCA by alicejenny

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									AB
                          Guidance on
                          The Design, Selection,
                          Installation and Use of
                          Uninterruptible Power
                          Supplies Onboard Vessels




 International Marine
Contractors Association
                                                 IMCA M 196
                                                     April 2009
www.imca-int.com
                            AB
The International Marine Contractors Association
(IMCA) is the international trade association
representing offshore, marine and underwater
engineering companies.

IMCA promotes improvements in quality, health, safety,
environmental and technical standards through the publication
of information notes, codes of practice and by other
appropriate means.

Members are self-regulating through the adoption of IMCA
guidelines as appropriate. They commit to act as responsible
members by following relevant guidelines and being willing to be
audited against compliance with them by their clients.

There are two core activities that relate to all members:
   Competence & Training
   Safety, Environment & Legislation

The Association is organised through four distinct divisions,
each covering a specific area of members’ interests: Diving,
Marine, Offshore Survey, Remote Systems & ROV.

There are also four regional sections which facilitate work on
issues affecting members in their local geographic area –
Americas Deepwater, Asia-Pacific, Europe & Africa and Middle
East & India.


                                IMCA M 196

This report was prepared for IMCA, under the direction of its
Marine Division Management Committee, by Noble Denton
Consultants Ltd.


                     www.imca-int.com/marine



    The information contained herein is given for guidance only and endeavours to
    reflect best industry practice. For the avoidance of doubt no legal liability shall
 attach to any guidance and/or recommendation and/or statement herein contained.
          Guidance on The Design, Selection, Installation and Use of
              Uninterruptible Power Supplies Onboard Vessels

                                                                   IMCA M 196 – April 2009




Summary ........................................................................................................................ 1
List of Abbreviations ..................................................................................................... 2
1     Introduction ........................................................................................................... 3
        1.1     Acknowledgements and Contributions ............................................................................................................ 3
        1.2     UPS Definition ......................................................................................................................................................... 3
        1.3     Purpose of this Document ................................................................................................................................... 3
        1.4     Survey of Vessel UPS and DC Power Supply Installations ........................................................................... 3
        1.5     List of Manufacturers ............................................................................................................................................. 4

2     Type of UPS Used Onboard Vessels ................................................................... 5
        2.1     UPS Internal Topology .......................................................................................................................................... 5
        2.2     Standby UPS ............................................................................................................................................................. 5
        2.3     Ferro-Resonant Standby UPS .............................................................................................................................. 6
        2.4     Line Interactive UPS .............................................................................................................................................. 6
        2.5     Online UPS ............................................................................................................................................................... 7
        2.6     Delta Online UPS ................................................................................................................................................... 8
        2.7     Manual Bypass ......................................................................................................................................................... 8
        2.8     UPS Features ........................................................................................................................................................... 8
        2.9     Testing UPSs at Annual DP and Field Arrival Trials ...................................................................................... 9
        2.10    Qualifying UPSs for Marine Applications .......................................................................................................... 9
        2.11    Types of Batteries for UPS .................................................................................................................................. 9

3     Types of DC Power Supplies Used on Vessels ................................................. 10
        3.1     DC Power Supplies Topology .......................................................................................................................... 10
        3.2     System Specification ............................................................................................................................................ 10
        3.3     Types of Batteries for DC Power Supplies .................................................................................................. 11

4     Types of Batteries Used Onboard Vessels ........................................................ 12
        4.1     Battery Definitions .............................................................................................................................................. 12
        4.2     Types of Secondary Batteries........................................................................................................................... 12
        4.3     Types of Lead Acid Batteries ........................................................................................................................... 12
        4.4     Types of Nickel-Cadmium Wet Cell Batteries ............................................................................................ 13
        4.5     Advantages and Disadvantages of Battery Types ........................................................................................ 14
        4.6     Battery Maintenance ........................................................................................................................................... 14
        4.7     Battery Inspection ............................................................................................................................................... 15
        4.8     Battery Load Testing and Alternatives........................................................................................................... 15
        4.9     Conductance Testing FAQ ............................................................................................................................... 16
        4.10    Battery Charging .................................................................................................................................................. 17
        4.11    Battery Cell Temperature ................................................................................................................................. 18

5     Application of UPS and DC Supplies Onboard Vessels................................... 20
        5.1     General .................................................................................................................................................................. 20
       5.2     UPS for Control Systems .................................................................................................................................. 20
       5.3     UPS for Voice and Data Communication Systems ..................................................................................... 21
       5.4     UPS for Safety Related or Critical Systems .................................................................................................. 21
       5.5     UPS for Emergency Systems ............................................................................................................................. 21
       5.6     DC Supplies with Battery Backup – Application to Generation Systems ............................................. 21

6     Integration into Vessel Systems......................................................................... 23
       6.1     Electrical Considerations ................................................................................................................................... 23
       6.2     Run Time ............................................................................................................................................................... 23
       6.3     Harmonics ............................................................................................................................................................. 25
       6.4     Interface Systems Considerations – Alarms and Monitoring ................................................................... 26
       6.5     Dual Supplies to UPSs ........................................................................................................................................ 26
       6.6     ESD Requirements .............................................................................................................................................. 27
       6.7     UPS Systems DC Power Supplies – Fault Levels and Protection Discrimination ............................... 27
       6.8     Dual Voltage UPSs............................................................................................................................................... 27
       6.9     Common/Summary Alarm ................................................................................................................................ 28

7     Strategies for UPS and DC Distribution ........................................................... 29
       7.1     General .................................................................................................................................................................. 29
       7.2     Minimum Requirement ...................................................................................................................................... 29
       7.3     Distributed UPS Arrangement ......................................................................................................................... 31
       7.4     Centralised UPS Systems................................................................................................................................... 32
       7.5     Backup UPS ........................................................................................................................................................... 33
       7.6     Strategies for DC Power Supply Distribution ............................................................................................. 34
       7.7     Cross Connection of DC Power Supplies .................................................................................................... 34

8     Class Requirements for UPS, DC Supplies and Batteries............................... 36
       8.1     General .................................................................................................................................................................. 36
       8.2     Common Requirements .................................................................................................................................... 36
       8.3     Standards Organisations .................................................................................................................................... 36

9     Switching Arrangements .................................................................................... 44
       9.1     General .................................................................................................................................................................. 44
       9.2     Main and Backup Supplies to UPSs ................................................................................................................. 44
       9.3     Static Switches ...................................................................................................................................................... 45
       9.4     Changeovers at UPS Output or in the Distribution Scheme ................................................................... 46

10 Operational Issues ............................................................................................... 47
       10.1    Safety Considerations ......................................................................................................................................... 47
       10.2    Environmental Considerations ......................................................................................................................... 47

11 Suitability for Marine Applications .................................................................... 48
       11.1    General .................................................................................................................................................................. 48
       11.2    Construction for Marine Environment .......................................................................................................... 48
       11.3    Design for Marine Applications – UPS ........................................................................................................... 48
       11.4    Design for Marine Applications – DC Supply .............................................................................................. 50

12 References ............................................................................................................ 52
Appendices
1   UPS Qualification Checklist ............................................................................... 53
2   Data on UPS, DC Power Supplies and Batteries ............................................. 55
     Survey of Owners and Operators of UPS Equipment ............................................................................................ 55
     Survey of Owners and Operators of DC Equipment ............................................................................................. 58
     NDC Desktop Survey of UPS Types........................................................................................................................... 59
     VRLA Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation ............ 63
     Wet Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation ............... 66
Summary
This document was commissioned by the International Marine Contractors Association and is intended to
provide the reader with guidance on the design, selection, installation and use of UPSs and DC power supplies
for marine applications.

Information provided by IMCA members confirms that there is a very wide range of manufacturers supplying
UPSs to the marine sector. Most of these units are of commercial grade and of the online type, that is to say,
the inverter continuously supplies the load.

There is a wide variation in the cost, quality and capability of UPSs and purchasers should carefully consider and
understand the required application and the electrical and environmental conditions in which the UPS or DC
power supply will be expected to operate.

Features and levels of performance cannot be taken for granted and standards for UPS design assume that
much of the specification for performance will be agreed between the purchasers and the supplier. Therefore,
simply making reference to a particular standard in a specification document does not necessarily guarantee the
unit will be fit for purpose.

In addition to poor choice of equipment for particular applications, the investigation revealed that premature
battery failure is a key issue in UPS reliability and maintainability. Thus the guidance provided concentrates
heavily on the maintenance and testing of batteries and on the advantages and disadvantages of different battery
types.




IMCA M 196                                                                                                       1
List of Abbreviations
ABS        American Bureau of Shipping             LCD     Liquid crystal display
AC         Alternating current                     LED     Light emitting diode
AGM        Absorbed glass Mmat/absorptive glass    LRS     Lloyds Register
           micro-fibre
                                                   MCB     Main circuit breakers
Ah         Amp hour                                MF      Maintenance free
AHC        Anti heave compensation
                                                   MODU    Mobile offshore drilling unit
AVR        Automatic voltage regulator
                                                   MSB     Main switchboard
BCR        Breaker close relay                     MSC     Maritime Safety Committee
COSWP      Code of Safe Working Practices for
                                                   NDC     Noble Denton Consultants Ltd
           Merchant Seamen
                                                   NiCaD   Nickel-cadmium
DC         Direct current
                                                   NMEA    National Marine Electronics
DDP        Deep discharge protection                       Association
DG         Distributed generation
                                                   PC      Personal computer
DNV        Det Norske Veritas                      PCB     Printed circuit board
DOD        Depth of discharge
                                                   pf      Power factor
DP         Dynamic positioning
                                                   PLC     Programmable logic controller
DSP        Digital signal processing               PMG     Permanent magnet generator
ECU        Electronic/environmental control unit
                                                   PMS     Power management system
EG         Emergency generator
                                                   RCS     Remote control system
ESD        Emergency shut down                     RCU     Remote control unit
FMEA       Failure modes and effects analysis
                                                   RMS     Route mean squared
HSE        Health & Safety Executive (UK)
                                                   ROV     Remotely operated vehicle
HV         High voltage                            SBC     Single board computer
IAS        Integrated automation system            SCR     Silicon control rectifier
IEC        International Electro Technical
                                                   SLA     Sealed lead acid
           Committee
                                                   SLI     Starting, lighting and ignition
IEEE       Institute of Electrical & Electronic
           Engineers                               SOLAS   Safety of Life at Sea
IMO        International Maritime Organization     SWBD    Switchboard
IP         Ingress protection                      TMS     Thruster management system
ISM        International Safety Management         UPS     Uninterruptible power supply
ISO        International Standards Organisation    VA      Volt-amperes
IT         Information technology                  VFD     Variable frequency drive
kV         Kilo volt                               VMS     Vessel management system
kVA        Kilo volt ampere                        VRLA    Valve regulated lead acid
kVAr       Kilo volt ampere reactive               VRPP    Valve regulated pocket plate
kW         Kilowatt                                VT      Voltage transformer
LA         Lead acid                               WCFDI   Worst case failure design intent




2                                                                                            IMCA M 196
1     Introduction
This document provides guidance on the design, selection, installation and use of uninterruptible power
supplies (UPS) for marine applications.


1.1      Acknowledgements and Contributions

         Thanks are due to the following companies for their contribution to this document:
            Norco Group Ltd – www.norcoenergy.com
            Transocean Engineering, Houston – www.deepwater.com
            Knutsen OAS Shipping AS – www.knutsenoas.com
            Converteam – www.converteam.com
            Kongsberg Maritime – www.km.kongsberg.com
            Helix Energy Solutions – www.helixesg.com
            Technip – www.technip.com


1.2      UPS Definition

         IEC/EN/BSI standard 62040-3, ‘Uninterruptible Power Systems (UPS)’ defines an uninterruptible
         power system as:

         A combination of converters, switches and energy storage means, for example, batteries, constituting a power
         system for maintaining the continuity of load power.

         Although most standards on UPSs deal only with units providing an AC output, this guidance
         document will also consider DC power supplies employing batteries as they share many of the same
         issues with AC UPSs.


1.3      Purpose of this Document

         This document is intended to provide information on the design, selection, installation and use of UPSs
         for marine applications. This is a very large subject which touches upon complex issues in electrical
         power engineering. The intention is to provide the reader with an understanding of the main issues to
         aid in the preparation of specifications and maintenance regimes. Issues associated with design and
         installation are also discussed. However, much still depends on the experience and competence of
         both purchaser and vendor.


1.4      Survey of Vessel UPS and DC Power Supply Installations

         A survey of vessel UPS and DC power supply installations was carried out in the process of preparing
         this document. Some of the information was received from members in response to information note
         IMCA M 12/08. Other information was taken from Noble Denton Consultants Ltd’s (NDC) archive
         of FMEAs carried out on dynamically positioned (DP) vessels. A sample of 15 vessels of various types
         was studied including DP Class 2 and DP Class 3 drilling rigs, pipelayers and construction vessels with
         some respondents providing general commentary on equipment used across their fleet. The
         information obtained is presented in tabular form in Appendix 2 and a summary of the findings is
         presented below.

         The survey revealed that there are a very large number of manufacturers providing UPSs used
         onboard vessels. Seventeen different brands of UPS and DC supply were identified from the sample
         but an internet search suggests there are many more. Further investigation revealed that certain
         groups of well known brands are owned by the same parent company. Most of the units were of the
         online type (also known as double conversion) but other types of UPS are in use onboard vessels
         including ferro resonant types and line interactive units. No examples of the more basic standby UPS
         were noted but these may be found in minor roles for backing up non essential PCs, etc. A more
         detailed discussion of these different types of UPS is given in Section 2.


IMCA M 196                                                                                                          3
      As might be expected, the UPS brands favoured by the major DP and vessel management system
      providers feature strongly. In particular, one well known manufacturer of DC systems and nickel
      cadmium (NiCad) batteries features strongly in the section on DC power supplies for switchboard
      controls.

      Although some UPS manufacturers do offer a range of ‘marine’ UPSs, most units appear to be
      commercial units intended for the protection of small to medium sized IT equipment such as servers
      in offices and factories. In many cases, the UPS unit is repackaged by a third party supplier into a more
      rugged enclosure which may include anti-vibration mounts, MCBs for the distribution system, the
      batteries and external bypass circuits. There are few reports of dissatisfaction with the performance
      of online units but problems have been reported with ferro-resonant and line interactive types.

      UPSs for propulsion and vessel control applications tend to be in the range 2kVA to 15kVA at 110V or
      220V single and three phase output. Output voltages include 110V, 230V or 480V single or three
      phase with some two phase units.

      Most vessels reported their main source of UPS problems as unexpected battery failure. In the course
      of the survey, it was noted that there is also a very large range of battery manufacturers offering a
      wide variety of battery types and models. It was further noted when studying the technical
      specification of UPSs that it could be difficult to determine exactly what type of battery was being
      offered with each UPS. This is quite significant as it is possible to specify batteries with very different
      expected lifespan. A much more detailed discussion of batteries and their characteristics is presented
      in Section 4.

      Following internal discussions, it was agreed that manufacturers’ names and model numbers should be
      replaced with a code. None of the products from manufacturers included in the survey was
      significantly worse than any other although some vessel owners did express a preference for one or
      two brands. In cases where there have been significant problems they are usually related to wrong
      application or poor specification rather than issues of quality.

      The most important lesson to be learnt is that in order to select a unit which is fit for purpose it is
      important to understand the limitations of the type of UPS being offered and the physical and electrical
      environment in which it will be operating. These issues should then be discussed and agreed with the
      UPS supplier. Appendix 1 provides a checklist to assist the vessel owner in this task.


1.5   List of Manufacturers

      The following list of UPS and DC power supply manufacturers was created from the survey of
      members’ replies to information note IMCA M 12/08 and reviews of archive information. The
      omission of a UPS manufacturer from this list does not imply unsuitability of their products for marine
      applications. In fact, a review of information in the public domain suggests that there are many more
      manufacturers that may be worthy of consideration.
         APC                       General Electric           MGE                        Siemens
         Best UPS                  HHI                        Powec                      Socomec
         Cigentec                  Jotec                      Power Innovations          Toshiba
         Eltek                     Marathon                   Powerware                  XP
         Enersys                   Mastervolt                 SAFT




4                                                                                                      IMCA M 196
2     Type of UPS Used Onboard Vessels

2.1      UPS Internal Topology

         This section presents an overview of the theory of operation of different types of UPS. When
         specifying a UPS for a particular application, it is vitally important to know what technology is being
         offered by any given vendor as some technologies are more suitable than others for certain
         applications.

         The capability, performance and reliability of a UPS is dependent both on the quality of the power
         supply to which it is connected and the electrical characteristics of the load it supplies. Commercial
         UPSs are optimised to be competitively priced and efficient in operation and are tailored to their
         primary role. The main market for UPSs is protection and continuity of supply to shore-based
         computer systems and other IT equipment. In recent times, industry standards have improved the
         ride-through capability of this type of equipment to the point where the short supply interruptions
         associated with some UPS topologies do not affect the operation of the load. Although UPSs are used
         to supply similar types of loads on vessels, the same level of ride-through capability should not be
         assumed. Similarly, in the developed world, utility power supplies are generally very stable, in both
         frequency and voltage and of low harmonic content. Again, UPS designers take advantage of this in
         developing and optimising their products. Power system quality is generally much poorer in most
         marine applications and can be particularly bad on vessels with large electric propulsion and drilling
         loads.

         Some vendors do offer a range of marine UPSs and many commercial UPSs are suitable for use on
         poor quality marine power systems. However, it is important to note that industry standards for
         UPSs, such as IEC 62040-3, require the buyer and vendor to agree many aspects of the specification if
         the operating conditions are unusual. Therefore, simply quoting UPS standards in a vessel specification
         without additional information and qualification may not ensure that a UPS system is fit for purpose.

         At the most basic level, there are only two types of UPS defined as ‘online’ and ‘standby’. In a standby
         UPS, the load is normally supplied directly from the main AC input by way of a filter. The unit
         switches to inverter-battery mode on detection of supply failure. In the online design, the load is
         always supplied from the inverter source and the battery is continuously charged during normal
         operation by way of the rectifier stage (or a separate battery charger). However, there are two types
         of online UPS and three distinct types of standby UPS which are sufficiently different in design to be
         recognised as types in their own right. Therefore, in practical terms, there are essentially five main
         types of UPS:
            Standby UPS;
            Ferro-resonant standby UPS;
            Line interactive standby UPS;
            Online UPS;
            Online Delta UPS.


2.2      Standby UPS

         The simplest form of UPS is the standby UPS. Figure 1 below shows the main components of such a
         system. In this design of UPS, the load is supplied from the main AC input by way of a filter and an
         auto-changeover (usually a static switch). The control system monitors the quality of the incoming
         power and switches the load to the inverter supply on detection of poor quality. However, the
         sophistication of the control system and the range of supply voltage parameters initiating a changeover
         may vary greatly from one model to the next. There is a short supply interruption during transfer to
         inverter mode. The transfer time is typically quoted as 4ms but detection times may extend this. As
         the zero-voltage ride-through time of commercial IT equipment power supplies is generally taken to
         be of the order of 10ms, this type of UPS works well in its intended application. This includes the
         protection of individual PCs in shore-based applications but does not guarantee that it will be effective
         or reliable in marine applications. The reason for this is that poor quality marine power supplies
         require the inverter to switch on and off more frequently than shore-based applications. The load will
         also be exposed to any supply voltage and frequency variations and transients which do not cause a

IMCA M 196                                                                                                       5
      changeover to inverter mode. Thus the quality of the power delivered to the load is dependent on
      the quality of the line conditioning and the sophistication of the control circuitry. Even in its intended
      market, this type of UPS is generally only specified for very small loads and is generally not
      recommended for use in the propulsion and control systems of modern vessels.

                                SENSE LINE             CONTROL
                                                         CCT


                              LINE                                                               OUTPUT
                           CONDITIONING                                                          CIRCUIT
                                                                                                BREAKER
       MAIN AC
        INPUT

                              FILTER        BATTERY CURRENT                   BATTERY CURRENT
                                              FLOW DURING                       FLOW DURING                          LOAD
                                                NORMAL                         STORED ENERGY
                                               OPERATION                           MODE


                                                 Figure 1 – Standby UPS


2.3   Ferro-Resonant Standby UPS

      Refer to Figure 2. The ferro-resonant UPS is a development of the simple standby UPS in which the
      changeover switch is replaced by a ferro-resonant transformer. Such transformers are carefully
      designed to form a resonant circuit in combination with suitable capacitance. By designing the
      transformer to operate in saturation, considerable voltage variation can be tolerated without switching
      to inverter mode and battery supply. As the ferro-resonant transformer’s primary role is in line
      conditioning, it is ideally suited as a line conditioner for the main AC supply. Because it operates as a
      resonant circuit, the transformer will also continue to provide an output voltage during the short
      interruption between detecting loss of the main supply and start up of the inverter.

      On marine power systems there can be significant swings in frequency. Because the ferro-resonant
      transformer is effectively synchronised to main AC input it cannot protect the load from changes in
      the steady state frequency and thus will transfer to battery power in this case. Although very popular
      at one time, the ferro-resonant transformer has largely been replaced by line interactive and online
      type UPSs for reasons of size and cost. This type of UPS is no longer recommended for use in the
      propulsion and control systems of modern vessels.

       MAIN AC                                                                                          OUTPUT
        INPUT                                                                                           CIRCUIT
                                                                                                       BREAKER


                                          SENSE LINE

                                                                                                                      LOAD
                                LINE                              CONTROL
                             CONDITIONING          BATTERY          CCT
                                                   CHARGER

                                                                                      FERRO-RESONANT
                                                                                       TRANSFORMER
                                FILTER




                                                                 INVERTER
                                             BATTERY




                                              Figure 2 – Ferro-resonant UPS


2.4   Line Interactive UPS

                 The line interactive UPS represents a further advance in the design of the standby UPS.

      Figure 3 shows the arrangement of the main components. In this type of UPS there is a single power
      converter capable of bi-directional operation. During periods when the quality of the main AC input
      power remains within acceptable limits, the filtered mains power is fed directly to the load and the
      converter acts as a battery charger. On detecting that the input power has failed, or is no longer
      within tolerance, the converter reverses its direction of power conversion and feeds the load. Line

6                                                                                                                 IMCA M 196
         interactive UPSs still account for a large share of the low and medium power range and offer cost
         effective protection. For their intended role in shore-based IT systems, they have been optimised to
         the point where many consider them to be the equal of online UPSs. They are generally more
         efficient than online UPSs because they only have one stage of power conversion instead of two. For
         most of the time the power converter is acting as a battery charger at very low load and thus its
         losses are also low. Like all standby UPSs much of its efficiency comes from the fact that the input
         power quality is expected to be good with only infrequent transfers to inverter mode. This may not
         be the case in some marine applications. In the worst case, the unit may operate on battery supply so
         frequently that the battery becomes depleted leading to a switch back to bypass mode regardless of
         power quality. Although there are a number of modern vessels using line interactive UPSs in
         propulsion systems, the online or double conversion UPS is preferred where isolation from poor
         quality power and security of supply is the main consideration.

                                LINE
                             CONDITIONING

             MAIN AC                                                                            OUTPUT
              INPUT                                                                             CIRCUIT
                                                                                               BREAKER
                                 FILTER



                                                                                                                 LOAD
                                 SENSE LINE                            CONTROL
                                                                         CCT        STATIC
                                                                                 CHANGEOVER
                                            BATTERY                                SWITCH
                                            CHARGER




                                                                      INVERTER
                                              BATTERY




                                               Figure 3 – Line interactive UPS


2.5      Online UPS

         The online or double conversion UPS is considered to provide the highest level of isolation from poor
         quality supplies. As its name suggests, the load is always supplied by the inverter. Figure 4 shows the
         arrangement of the main components. A common line-conditioning stage supplies the rectifier/battery
         charger and the automatic bypass line. As is the case with the standby UPS, either the inverter output
         or the bypass line is selected by a static (solid state) switch. Unlike the standby UPS, the inverter
         supply is the normal supply. In theory, the automatic bypass is not essential to the operation of an
         online UPS. In practice, the bypass is provided to cover for failure or overload of the inverter. Some
         online UPSs have an ‘economy mode’ in which their mode of operation changes to standby mode
         while power quality is good. The inclusion of such a feature in a UPS specification is unlikely to be
         important for marine applications and may even be undesirable.

                                        SENSE LINE                 CONTROL
                                                                     CCT

                               LINE
                            CONDITIONING
                                                     BYPASS
             MAIN AC                                                                      OUTPUT
              INPUT                                                                       CIRCUIT
                                                                                         BREAKER
                               FILTER



                                                                                                          LOAD




                             BATTERY
                             CHARGER




                                                                   INVERTER
                                            BATTERY




                                                       Figure 4 – Online UPS

IMCA M 196                                                                                                              7
2.6   Delta Online UPS

      The delta online UPS is a patented concept which offers a significant improvement in efficiency over
      the conventional double conversion online UPS. The designers claim that it is suitable for use with all
      types of generators. As it requires no input filter, it may also help to avoid the problems associated
      with adding filters to power systems with a high harmonic content. The delta online UPS is a relatively
      recent concept and as such may have had limited exposure to the marine market but vessel owners
      may wish to carry out further evaluation of this novel design to see what advantages it provides. In
      very basic terms, the theory of operations is that the current in one winding of a differential (delta)
      transformer is controlled by a rectifier-battery-inverter combination producing the desired voltage
      and frequency (but not the load current). This in turn controls the current in the other winding of the
      delta transformer and thus the load voltage. In the event that the supply voltage fails, the inverter and
      battery supply the load as they would in a conventional double conversion UPS.




                                                                                      DELTA
                                                                                   TRANSFORMER




                                                                           LOAD




                                        Figure 5 – Delta online UPS


2.7   Manual Bypass

      Most UPSs offer a manual bypass facility. Some classification societies require that this is physically
      separate from the UPS enclosure if the UPS is used to supply emergency services. By the same rule,
      the power distribution would have to be separate from the UPS enclosure to ensure the desired level
      of independence. Most manual bypass facilities are included in the UPS enclosure along with the
      batteries and the circuit breakers for power distribution.


2.8   UPS Features

      UPSs can be purchased with a very wide range of features depending on the size and cost of the unit.
      Even fairly modest UPSs make use of digital signal processing (DSP) technology as a part of their
      control functions.

      Diagnostics: UPSs can now provide a great deal of information on a range of conditions including
      converter health, control systems health and battery condition.

      Battery curves: In UPS units which can accept different types and numbers of batteries, it is possible
      to load different battery discharge characteristics into the control systems. This information is used
      to control advanced charging systems and also to provide a ‘fuel gauge’ type indication of remaining
      time on batteries.



8                                                                                                    IMCA M 196
         Voltage regulation: In the simplest online UPSs, the output voltage is determined by the DC link
         voltage level which falls steadily when the battery is being discharged. More sophisticated UPSs use a
         dc/DC converter between the battery and the DC link to maintain the output voltage within tight
         tolerances.

         Deep discharge protection: Some manufactures fit deep discharge protection to prevent the
         batteries being damaged by a deep discharge. One problem with this type of protection is that it may
         reduce the time on batteries as they age. Such features generally disconnect the load when the
         battery voltage has fallen to a predetermined level.

         Graceful shutdown alarm: Most UPSs of the size found onboard vessels are capable of providing a
         control signal which can instruct the load being supplied to shut down in a graceful manner. This
         function could be used to prevent hard drive failure in VMS operator stations but is not generally used
         in marine applications. Where this feature is more commonly used is in UPSs for the control systems
         of variable speed drives. In some designs of modern drives there is a risk of damage to the drive if the
         control system fails or power to the control system is lost. A small UPS with a run-time of around 10
         minutes can be used to protect the drive against failure of the auxiliary power supply. As soon as the
         UPS detects that mains power has been lost the UPS will signal the drive to commence a graceful
         shutdown before the batteries expire.

         Hot swap batteries: UPSs with this feature have already been fitted to some members’ vessels.
         The batteries are in slide-out trays that can be removed a bank at a time without the UPS dropping
         the load.


2.9      Testing UPSs at Annual DP and Field Arrival Trials

         Battery endurance testing is a feature of the annual trials carried out by DP Class 2 and DP Class 3
         vessels. Some vessels also carry out battery endurance tests as part of the field arrival trials. In some
         cases this could mean that UPS batteries are being discharge tested every month. Classification
         society rules require that UPS batteries supply the load for at least 30 minutes. Battery life is affected
         by the number and depth of discharge cycles that the battery experiences in a given time.

         With this in mind, it may be prudent to confirm that the batteries are not being over-tested to the
         point where reliability is actually reduced by testing, not enhanced. Similarly, when determining the
         battery capacity required of a UPS, vessel owners may wish to include a margin for routine testing that
         ensures the battery will not be damaged. Care should also be taken that any margin is not eroded by
         the addition of extra loads. Experience shows that the demand for UPS power grows throughout the
         life of a vessel as modifications and enhancements are added to the DP controls and other systems.
         Additional position reference systems, sensors, monitors, data recorders and bridge PCs all place
         extra demands on existing UPSs.


2.10     Qualifying UPSs for Marine Applications

         UPSs for marine applications can be qualified initially by a review of the UPS design against the
         required specification.

         The power systems of drilling rigs present a particular challenge for UPSs and some drilling
         contractors have experienced significant problems with UPSs failing due to the overload of internal
         components. One major drilling contractor has even gone so far as creating its own method for
         qualifying UPSs for use on power systems with high levels of harmonics and commutation notches
         associated with drilling drives. The qualifying procedure involves operating the UPS from a test rig
         consisting of a small generator driving a 6 pulse variable speed drive to recreate typical drilling system
         distortion. The performance of the UPS is closely monitored during an extended test period to prove
         reliability of operation in all modes and the quality of the output power that it is able to provide. This
         type of qualification procedure should be considered by any vessel owner with similar power system
         problems.


2.11     Types of Batteries for UPS

         The vast majority of UPSs use a VRLA (lead acid) battery of various types. See Section 4 for more
         detail on the advantages and disadvantages of various battery types.

IMCA M 196                                                                                                        9
3     Types of DC Power Supplies Used on Vessels

3.1      DC Power Supplies Topology

         System terminology: In its simplest form, the DC power supply consists of a battery charger,
         battery bank and distribution system with associated protection. The term ‘battery charger’ is
         misleading and these units should more properly be called rectifier control units as they are capable of
         delivering the full power requirements of the system without contribution from the battery.

         Voltage levels: 110V DC power supplies are traditionally used for high voltage switchboard control
         systems. Engine and thruster controls are typically supplied at 24V DC. Applications are considered
         in more detail below under ‘Installation monitoring’.

         Battery management: This feature is key to ensuring the longevity of battery banks and multi stage
         charge with a boost, absorption and float stage are commonplace now. It should be noted that
         battery types cannot be interchanged without consideration of the battery charging systems. In
         particular, chargers used for lead acid batteries cannot be used for nickel cadmium batteries unless
         designed for dual purpose operation. Adjustment or a change of charger may also be required
         between different types of lead acid batteries and manufacturers’ guidelines should be followed.

         Association of major components: Figure 6 and Figure 7 show two possible physical
         configurations of the major elements of a DC system. The arrangement in Figure 7 offers the
         advantage of being able to isolate the battery bank without having to disconnect the distribution.

             AC SUPPLY
                                                                         BATTERY
                                                                                                       DISTRIBUTION
                                                                          BANK



                         Figure 6 – Linear configuration of rectifier, battery bank and distribution

             AC SUPPLY
                                                                         BATTERY
                                                                                                       DISTRIBUTION
                                                                          BANK




                         Figure 7 – Branch configuration of rectifier, battery bank and distribution

         Installation monitoring: Installation monitoring of the system for over/under voltage, over-current
         and earth fault should be a minimum requirement.


3.2      System Specification

         When specifying a DC supply system for a particular application, it is important to know what battery,
         charger and distribution system technology is being offered by any given vendor as some technologies
         are more suitable than others for certain applications.

         The capability, performance and reliability of a DC supply system is dependent both on the quality of
         the power supply to which it is connected and the electrical characteristics of the load it supplies.
         Power system quality is generally much poorer in most marine applications and can be particularly
         poor on vessels with large electric propulsion and drilling loads.

         The type of battery bank used has to take into account the following:
             the regulations and requirements of the certification authorities;
             the duration (ampere hour) system requirements;
             the supply voltage system requirements;
             the current level system requirements;
             location considerations (corrosive effects, ventilation);

10                                                                                                          IMCA M 196
            ventilation requirements and maintained battery bank cell temperature;
            battery electrolyte spillage containment;
            fault level capability (ability to supply system fault levels and maintain voltage levels);
            IP classification of enclosure;
            maintenance/inspection requirements.

         The type of charger (rectifier control unit) used has to take into account the following:
            the regulations and requirements of the certification authorities;
            the supply voltage quality;
            the output voltage quality (maintained voltage levels and ripple factor);
            the charge requirements of the batteries;
            the monitoring and alarm requirements of the system;
            interface alarms requirements to VMS;
            the internal protection requirements;
            the external protection requirements of the distribution system;
            fault level capability (ability to supply system fault levels and maintain voltage levels);
            IP classification of enclosure;
            maintenance requirements.

         The type of distribution system used has to take into account the following:
            the regulations and requirements of the certification authorities;
            monitoring of system voltage and current’
            type of system grounding – either ‘intentionally grounded’ or ‘floating’ with ground fault
             protection;
            alarm requirements of the system (interface alarms to VMS);
            the internal protection requirements of feeder and outgoing breakers (overload and short circuit
             protection);
            co-ordination of protection with battery charges, battery bank and outgoing feeders;
            IP classification of enclosure;
            isolation and lock off facilities of supplies and feeders;
            maintenance/inspection requirements.


3.3      Types of Batteries for DC Power Supplies

         Vessel survey results in Appendix 2: The survey results do not contain many examples of DC
         systems, however the limited results indicated that DC systems utilise wet cell batteries.

         Desktop study results in Appendix 2: The survey results confirm that the majority of DC
         systems currently in use utilise wet cell batteries.




IMCA M 196                                                                                                 11
4     Types of Batteries Used Onboard Vessels

4.1      Battery Definitions

         Primary batteries: Primary batteries are designed to transform chemical energy into electrical
         energy. When the initial supply of energy reactants is exhausted it cannot be restored to the battery
         by electrical means.

         Secondary batteries: Secondary batteries are designed to transform chemical energy to electrical
         energy like primary batteries. However, when the supply of energy reactants is depleted or exhausted
         the batteries can be recharged. Secondary batteries can have their chemical reactions reversed by
         supplying electrical energy to the cell and therefore restoring their original composition. Although
         rechargeable batteries may be refreshed by charging, they suffer degradation primarily through
         charging, discharging, age and environmental (temperature) operating conditions.

         Battery shelf life: This is the time an inactive battery can be stored before it becomes unusable.
         When a battery has reached 80% of its initial capacity, it is usually considered unfit for usage.

         Battery calendar life: This is the elapsed time before a battery becomes unusable whether it is in
         active use or inactive.


4.2      Types of Secondary Batteries

         Two basic battery technologies are used onboard vessels, lead acid and nickel cadmium.

         Secondary batteries can be categorised as follows:
            open vent (wet or flooded cell) batteries;
            sealed (valve regulated vent) batteries;
            dry (valve regulated vent) batteries.

         The categorisation of battery types into wet, sealed and dry batteries is not as precise as the names
         may suggest as most higher power batteries that are said to be sealed or dry are valve regulated. This
         design feature allows gas to be expelled in abnormal circumstances. Valve regulated nickel cadmium
         cannot be classed as dry as all the electrolyte is not absorbed by the glass mat.

         The chemical types of batteries also fall into two basic categories these being:
            lead acid batteries (open vent, sealed and dry);
            nickel cadmium (open vent and sealed).

         Some other derivatives of the nickel battery and lead acid types have been listed. The smaller nickel
         based dry types have not been considered for marine application due to their limited capacity and
         usage within the industry.


4.3      Types of Lead Acid Batteries

         Wet cell (flooded) open vent: This is the standard lead acid battery. Within this type of battery
         range there is a large selection of batteries with high specification and advanced technology which has
         proven to be reliable over a long period of time.

         Valve regulated lead acid (VRLA): The VRLA battery also called ‘sealed lead acid (SLA)’ is one of
         many types of lead acid batteries, also known as maintenance free (MF). In a VRLA battery, the
         hydrogen and oxygen produced in the cells recombine back into water. In this way there is no leakage
         and the battery can be considered to be maintenance free. This construction is designed to prevent
         electrolyte loss through evaporation, spillage and gassing and this in turn prolongs the life of the
         battery. Instead of simple vent caps on the cells to let gas escape, VRLA types have pressure valves
         that open only under extreme conditions. Valve regulated batteries also need an electrolyte design
         that reduces gassing by impeding the release to the atmosphere of the oxygen and hydrogen generated
         by the galvanic action of the battery during charging. This usually involves a catalyst that causes the

12                                                                                                     IMCA M 196
         hydrogen and oxygen to recombine into water and is called a recombinant system. Because spillage of
         the acid electrolyte is eliminated, the batteries are also safer. There are two main types of VRLA
         batteries which are discussed below.

         Valve regulated lead acid – absorbed glass mat battery (AGM): Also known as ‘absorptive
         glass microfibre’; AGM is used in VRLA batteries such that the boron silicate fibreglass mat acting as
         the separator between the electrodes and absorbing the free electrolyte acting like a sponge. Its
         purpose is to promote recombination of the hydrogen and oxygen given off during the charging
         process. The fibreglass mat absorbs and immobilises the acid in the mat but keeps it in a liquid rather
         than a gel form. In this way the acid is readily available to the plates allowing fast reactions. This
         construction is robust and able to withstand severe shock and vibration and the cells will not leak
         even if the case is cracked. AGM batteries are also sometimes called ‘starved electrolyte’ or ‘dry’,
         because the fibreglass mat is only 95% saturated with sulphuric acid and there is no excess liquid.
         Nearly all AGM batteries are sealed valve regulated VRLA. This is the most common battery utilised
         for UPS systems found during this study.

         Valve regulated lead acid – gel battery: This is a rechargeable valve regulated lead acid battery
         with a gelatinous electrolyte. The gel batteries virtually eliminate the electrolyte evaporation, spillage
         and therefore corrosion issues. It has a good resistance to extreme temperatures, shock and
         vibration and is therefore utilised in automobiles, boats, aircraft and other motorised vehicles. These
         batteries are often referred to as sealed lead-acid (SLA) batteries due to their non-leaking containers
         but they are not completely sealed, valve regulation allows for gas to be expelled. Chemically, they
         are the same as wet (non-sealed) batteries except that the antimony in the lead plates is replaced by
         calcium. The battery type is often referred to as a lead-calcium battery.

         Deep cycle batteries: Often listed as for ‘marine applications’, these deep cycle batteries are
         designed to be completely discharged before recharging. Because charging causes excessive heat
         which can warp the plates, thicker and stronger or solid plate grids are used for deep cycling
         applications. With reference to marine application, the batteries are designed to supply equipment
         with longer intervals between recharging. They also have an engine starting capability and some
         models can perform a dual ‘domestic’/’starting’ role.

         SLI batteries (starting lighting and ignition): This is the typical automotive battery application.
         Automotive batteries are designed to be fully charged when starting the vehicle; after starting the
         engine, the lost charge, typically 2% to 5% of the charge, is replaced by the alternator and the battery
         remains fully charged. These batteries are not designed to be discharged below 50% depth of
         discharge (DOD) and discharging below these levels can damage the plates and shorten battery life.


4.4      Types of Nickel-Cadmium Wet Cell Batteries

         Wet cell (flooded) open vent: This is the standard nickel cadmium battery. Within this type of
         battery range, there is a large selection of batteries with high specification and advanced technology
         which has proven to be reliable over a long period of time.

         Nickel-cadmium fibre plate batteries: The nickel fibre matrix used for the fibre plate allows 90%
         of the electrode volume for holding the active material. This fibre structure provides good
         conductivity to ensure electrical performance. In addition, the nickel cadmium fibre plate technology
         uses active material free from graphite and iron. The elimination of graphite ensures that the
         electrolyte does not get carbonated and the elimination of iron reduces water consumption.

         Nickel-cadmium pocket plate batteries: Nickel-cadmium pocket plate batteries are said by the
         manufacturers to be the most reliable and rugged batteries available today. They can withstand to a
         great extent any type of abuse like overcharge, deep discharge, even accidental reverse charge, and
         can be stored in any state of charge.

         Nickel-cadmium valve regulated pocket plate batteries (VRPP): VRPP batteries work on the
         oxygen recombination principle and therefore have much reduced water consumption. The level of
         recombination of these cells is 85-95% whereas normal vented type cells have a 30-35% recombination
         efficiency. When the VRPP cells are properly float charged, the manufacturers list that they will not
         need to be topped off with water for nearly 20 years. If the levels do become low during the life of
         the battery, there are provisions to add water to the cells.



IMCA M 196                                                                                                       13
4.5   Advantages and Disadvantages of Battery Types

      Wet cell lead acid versus nickel-cadmium: There are many claims and counter claims from
      manufacturers of lead acid and nickel-cadmium wet cell batteries of the advantages and disadvantages
      of their product. Our research has found that this debate is less intense where the manufacturer
      supplies both types of batteries. Both lead acid and nickel-cadmium batteries are excellent products
      with a wide range and variety, offering numerous options to the design engineer. The specification
      requirements of the system design should be the dominant factor in deciding what type of wet cell
      battery should be used.

      Wet cell versus valve regulated lead acid (VRLA): The specification requirements of the
      system design should be the dominant factor in deciding what type of battery should be used. This
      option may not be fully conveyed to the designer or purchaser as our research has found that UPS
      manufacturers may not offer various choices or options. The general findings are that DC systems use
      wet cells and UPS systems use some variation of valve regulated lead acid battery technology. The
      dominant factor for UPS systems appears to be the provision of a safe and maintenance free battery.
      However, no battery should be considered to be entirely maintenance free as periodic inspection is
      beneficial in all cases.

      Types of valve regulated lead acid (VRLA): There are various types of VRLA batteries and
      general terminology has been found in UPS manufacturers’ information such as sealed battery, non
      spillage battery, dry battery. All non wet cell lead acid batteries have valve regulation.

      Life span: Manufacturers’ information on VRLA batteries is dominated by claims of battery lifespan.
      As the majority of manufacturers make a selection of battery types with quoted life spans of 3-5 years,
      5-8 years and 7-10 years, it should be possible to choose a suitable battery type. The dominant design
      specification is what design intent is set for the UPS system lifespan and, if the battery lifespan requires
      or can be selected to meet this same criteria, it could be concluded that the batteries with the longest
      lifespan should always be the choice. However, the owner or operator may have a policy of renewing
      all VRLA batteries every three to five years and this is an equally valid approach. It should be noted
      that the battery renewal costs may be 25 to 30% of the original cost of the UPS; therefore, renewal of
      the batteries three times may well be equal to the original project costs of the system.


4.6   Battery Maintenance

      Battery management: Battery management is a method of keeping the cells within their desired
      operating limits. This is achieved by ensuring the charging rate is correct, the discharge rate does not
      exceed the design intent (loading of system) and the environmental conditions are correct.

      Maintenance free: The term ‘maintenance free’ or ‘low maintenance’ may have lulled some users
      into a false sense of security that DC battery supply systems and UPS systems do not require
      maintenance. Detailed study of manufacturers’ information confirms that maintenance such as
      inspection and testing is still required. The terminology of maintenance free normally relates to the
      requirement to top up the battery electrolyte. For instance, if the charging condition is incorrect or
      one battery is faulty in a battery bank, overcharging can take place and VRLA or VRPP batteries will
      gas off. Also, if the temperature conditions have changed due to ambient or internal ventilation
      conditions (fan failures or blocked air inlets or outlets), batteries will overheat and can fail.

      Maintenance of wet cell (flooded) open vent: This is the standard lead acid or nickel-cadmium
      battery; manufacturers’ information will state the maintenance requirements inclusive of inspection
      and testing periods for various operational conditions. These requirements will vary depending on the
      battery technology and type.

      Maintenance of wet cell (flooded) advanced technology: Advanced battery technology, both in
      lead acid and nickel-cadmium batteries, has proven to be reliable over a period of time.
      Manufacturers’ information states the maintenance requirements inclusive of inspection and testing
      periods for various operational conditions. These requirements vary depending on the battery
      technology and type.

      Maintenance of valve regulated lead acid: VRLA batteries (both AGM and gel types) still require
      maintenance. Manufacturers’ information states the maintenance requirements inclusive of inspection
      and testing periods for various operational conditions. These requirements vary depending on the
      battery technology and type. The construction and installation conditions should also be considered;

14                                                                                                      IMCA M 196
         for instance, the UPS manufacturer instruction manual will not consider whether the UPS system has
         been housed in another panel as is often the case with ruggedised units.

         Battery storage: Figure 8 shows how battery capacity may reduce with time in storage at various
         temperatures. Actual performance will vary from one battery model to another.




                 Figure 8 – Reduction in battery capacity with time in storage at various temperatures


4.7      Battery Inspection

         Inspection: The inspection of batteries should be carried out on a regular basis. Visual inspection
         can highlight burned connections, battery cell distortion or cracked case. Also, this type of inspection
         may be combined with checking the temperature (heat status) of the cells within the battery bank.

         Heat status tests: Thermal imaging can be utilised to check for ‘hot spots’ which would indicate
         points of high thermal stress in the cell or the battery pack. These tests can assist in the identification
         of problems such as overheating, inadequate air flow and interference from neighbouring cells or heat
         from other components. The images can also be used to determine the best location for temperature
         sensors. Specialised thermal imaging cameras can be used to carry this out. A simple test can be
         carried out by a laser thermometer or similar handheld device. One problem with a heat status test is
         that batteries on a float charge may not draw sufficient current to reveal any issues. It is common for
         very large land based UPS installations (say 250kVA to 750kVA) to use a ‘ductor’ to test battery
         interconnections.


4.8      Battery Load Testing and Alternatives

         General information: Battery testing is a specialist subject and the information presented below
         has been developed from a report prepared on this subject for NDC by Norco Energy using
         information taken from the public domain. Information reviewed in the process of preparing this
         guidance highlighted that battery testing has an important role in establishing battery condition and
         therefore reliability. If battery condition is not known then battery backup systems have no known
         level of reliability.

         For most applications, the load test of a battery is the most efficient and most effective demonstration
         of fitness for service. However, alternative test methods have been developed in the last few years
         which are gaining acceptance and which can be performed more conveniently. Such testing could be
         used to supplement the traditional load bank test.

         Load testing: Using a UPS’s own consumers as the test load is the most common way to confirm
         battery endurance. Such tests are typically carried out at annual DP trials and field arrival trials. This

IMCA M 196                                                                                                        15
      type of testing provides confidence that UPS batteries have the necessary endurance but provides little
      in the way of diagnostic information about the long term health of the battery bank.

      Discharge testing: Discharge testing is the traditional way of testing battery banks. This type of
      testing is intrusive and involves isolating the battery from its system and connecting it to resistive load-
      banks. Each cell is tested and its performance compared against manufacturer’s specifications. The
      data from all of these tests is then electronically recorded and analysed by engineers. Historical data is
      combined with the latest test results to predict possible cell failures and make recommendations for
      prolonging battery life. Replacement cells and/or repairs are then provided where necessary.

      Conductance testing: Conductance testing is a modern alternative to discharge testing and has
      recently been added to the IEEE draft standard for testing sealed valve regulated lead acid batteries.
      Many battery manufacturers have adopted conductance testing. The Midtronic’s conductance tester
      has found acceptance amongst a range of battery users including major telecommunications
      companies.


4.9   Conductance Testing FAQ

      Increased awareness of conductance testing has generated questions about application and
      methodology. The following are answers to some of the most frequently asked questions.

      What is Ohmic testing technology? In simple terms, Ohmic battery testing technology refers to
      a range of techniques based on Ohm’s Law, which expresses the relationship between voltage, current
      and impedance in an electrical circuit.

      For a purely resistive circuit, Ohm’s Law can be expressed as follows: Volts (E) = Amperes (I) x Ohms
      (R). If any two of the three values of voltage (Volts), current (Amperes) or resistance (Ohms) are
      known, the third value can be calculated using the above expression. Thus, Ohmic testing technology
      attempts to use voltage and current measurements to determine the resistive characteristics of a
      battery. A higher than expected resistance equates to a reduced ability to produce current.

      What is conductance? Electrical conductance is a measure of how easily electricity flows. Test
      results show that, for low frequency measurements, the conductance of a battery is an indicator of
      battery health and has a linear correlation to the battery’s timed-discharge capacity test result. Thus a
      conductance measurement can be used as a reliable predictor of battery end-of-life.

      Why use conductance testing? Conductance testing offers advantages over other types of battery
      testing. Voltage and specific gravity measurements are not predictive. Timed discharge testing is very
      time-consuming and expensive. Other forms of impedance testing may not correlate directly and
      linearly with timed-discharge capacity.

      How is the conductance test performed? Test set leads are connected to the positive and
      negative posts of the cell or battery under test, a measurement is taken in a matter of seconds. There
      is no need for additional leads to be connected to the ends of the string or for clamp-on current
      measurements. Testing can be carried out when the battery system is online and at various states of
      charge.

      How can conductance readings be used? The conductance tester gives a quantitative
      measurement in Mhos (or Siemens) as well as a qualitative indication of battery health (percent or
      reference) related to a standard.

      Can conductance testers measure the condition of sealed valve-regulated batteries as
      well as flooded cells? Correlation studies have been performed on a significant number of valve
      regulated cell types. These studies have shown that conductance test results are very predictive of
      battery timed discharge capacity, while voltage measurements are shown to be of little value. Data for
      gelled batteries is also available.

      What kinds of batteries can be tested utilising conductance? Typically, any 2-12 Volt, lead-
      acid 5-2000 ampere-hour cells can be tested.

      Can nickel-cadmium (NiCad) batteries and cells be tested utilising conductance? The
      instrument will accurately measure the voltage and conductance of NiCad batteries. Conductance
      testing will measure and identify gross failures of NiCad batteries. The instrument will report hard


16                                                                                                      IMCA M 196
         shorts identified through low voltage and is a useful tool in testing the application of NiCad battery
         systems. The feature of forecasting the failure of cells is more challenging when testing NiCads. Due
         to the nature of their construction and chemistry, all NiCads will measure consistently (good) until
         there is a failure indicating the end of life. The instrument will indicate this failure after the fact, a
         limitation that is true of all Ohmic measuring devices, including all existing impedance and resistance
         testers on the market. The instrument contains a low voltage alarm, which is set by the user to a
         minimum of 1.50 Volts/DC cell. This will trigger an audible alarm when testing single cell NiCads
         falling below the voltage benchmark. Additionally, the instrument will not test any battery or cell
         where the measured voltage is below 1.0 Volts DC, which would include any badly discharged or
         shorted NiCad cells.

         Has conductance testing been proven and accepted by the international community?
         Extensive data has been gathered by the global telecommunications industry, battery manufacturers
         worldwide, international rail and transportation providers and the electric power industry. This data
         has been presented to the IEEE Standards Committee which now includes conductance testing in its
         draft standard for testing sealed valve-regulated batteries. Additionally, the data has also been
         presented to the International Lead Zinc Research Organisation, the Battery Council International and
         the International Telecommunications Energy Conference.

         Does battery temperature affect conductance measurement? The actual temperature of the
         battery needs to be considered when making a conductance test. Battery conductance reference
         values (or baselines) assume the optimal battery operating temperature of 77° Fahrenheit (25°
         Celsius). A calculation can be made to compensate for temperature variation. Conductance testers
         can automatically calculate the change in percent of reference.


4.10     Battery Charging

         General: Battery chargers and battery charge levels can be summarised as two basic categories.
            Battery chargers that can supply system load current, trickle (float) levels and boost levels. These
             systems are sometimes called rectifier control units;
            Battery chargers that supply trickle (float) levels.

         Direct current supply systems: The battery charger (rectifier control unit) supplies the system
         load and trickle (float) charge to the battery bank, if the system has been operating on battery power
         and the battery voltage has dropped. When the mains AC power is restored the battery charger will
         supply the system load and recharge the batteries, the battery charge condition may change from
         trickle (float) to boost mode depending on the battery voltage level, the battery type and the settings
         of the battery charger. Typically, a 110V DC system may boost charge at 138V DC.

         UPS supply systems with VRLA batteries: The battery chargers supply the trickle (float) charge
         to the battery bank. If the system has been operating on battery power and the battery voltage has
         dropped, the battery charger will trickle (float) charge the battery bank when the mains power is
         restored.

         Unapproved chargers: Unapproved battery chargers may be found on installed systems where
         different manufacturers’ equipment is installed or where retrofit work has taken place.

         Trickle (float): A trickle charger charges the battery slowly, normally at the self-discharge rate; this
         method of battery charging is the slowest method of charging. Batteries can be left in a trickle charger
         indefinitely to keep the battery ‘topped up’ but not overcharged.

         Boost charge: This is a method of fast charging a battery (or battery bank) from a low battery
         terminal voltage. This is normally one element of a battery charger and research carried out for this
         guidance document suggests this feature being applicable to wet cells only.

         Intelligent chargers: An intelligent charger will monitor the battery voltage change (may also
         measure temperature) and time under charge to determine the optimum charge current. This type of
         charger is often referred to as a ∆V or delta-V charger. Charging is finished when a combination of
         the voltage (may be temperature) and or time indicates that the battery is fully charged. An intelligent
         charger may fast charge a battery up to about 85% of its maximum capacity in under an hour and then
         switch to trickle charging.


IMCA M 196                                                                                                       17
       Pulse chargers: Direct current pulse charging technology requires a strictly controlled pulse rise
       time and width. This type of technology claims to work with any chemistry of batteries, including LA
       or NiCad wet cells and VRLA and VRPP batteries. Although this type of charger is not common in
       commercial marine applications, it has been installed on some DP vessels.

       Safety systems: Protection and alarm systems within the battery charger will ensure that batteries
       are not over- or under-charged.

       Battery failures due to inappropriate charging: The use of approved and intelligent chargers
       combined with safety systems will not extend battery life but will ensure that the battery life is not
       reduced by inappropriate charging or fault conditions. From the survey information and NDC’s
       experience, the level of this effect cannot be identified; however, from information collated,
       inappropriate charging and lack of safety systems is listed as a high battery failure effect.


4.11   Battery Cell Temperature

       VRLA battery cell temperature: This is the most significant factor affecting battery lifespan.
       Manufacturers state what the battery lifespan effect will be in respect of elevated temperature.
       Research carried out in the preparation of this guidance document suggests that this value is normally
       20° Celsius. At best, battery lifespan will decrease 20% per 5°C increase above nominal (20°C), see
       Figure 9 and Figure 10. Some literature reports an even greater effect on lifespan.

       Battery temperature: This may be affected by various factors such as ambient temperature,
       battery bank cell layout, cooling failure (fans, etc.) and charge/discharge rate conditions.




                      Figure 9 – Reduction in battery capacity with operating temperature




18                                                                                                  IMCA M 196
             Figure 10 – Effect of temperature on capacity ratio




IMCA M 196                                                         19
5      Application of UPS and DC Supplies Onboard Vessels

5.1   General

      Uninterruptible power supplies are used as an independent source of clean power for a wide range of
      functions on modern vessels. Information received from IMCA members in the process of preparing
      this guidance suggests that modern vessels can have as many as 25 dedicated UPSs and DC power
      supplies in their propulsion and vessel control systems alone.

      Applications for UPSs can be loosely divided into four main categories as shown below.
         control system;
         communication systems;
         safety systems;
         emergency systems.

      There are also some specialist roles for UPS supplies including pre-charging the DC links of thruster
      variable speed drives as part of blackout recovery.

      Applications for DC power supplies with battery backup included engines, thrusters and switchboard
      control systems. These applications are discussed in Sections 3 and 5.6.


5.2   UPS for Control Systems

      Typical control system applications include:
         engine control systems;
         propulsion and thruster controls systems;
         vessel and power management systems;
         DP systems;
         crane control systems;
         drilling control systems including AHC;
         pipelay control systems.

      For control systems, a UPS has three roles to perform:
         It must provide a clean source of power to the control system to isolate it from mains-borne
          interference such as spikes and harmonics and undesirable fluctuations in frequency and voltage
          which may occur in a vessel’s power systems. Note: Not all types of UPS are able to operate
          properly from poor quality power.
         It must provide power to the control, alarm and monitoring systems when the main power is
          unavailable such as during a blackout. In this role, the UPS provides power for remote control of
          the plant to allow automatic or manual blackout recovery to proceed rapidly.
         It must provide a warning to the vessel’s operators that power is being drawn from the batteries
          to allow time for a graceful transfer to another control system or to make safe the work in
          progress before control is lost.

      The required battery endurance depends very much on the application. In many cases, the battery
      may only be required to supply the load until an emergency generator connects in a matter of a few
      minutes or less. In other cases, a much longer period of autonomous operation may be required.
      Control system UPSs on DP vessels of Equipment Class 2 and 3 are expected to last at least
      30 minutes on battery supply but this requirement also appears in some main class rules as a ‘general
      requirement’ for standby power supplies.




20                                                                                                IMCA M 196
5.3      UPS for Voice and Data Communication Systems

         In communication systems, the primary role of the UPS is to provide conditioned power to a range of
         essential and non essential consumers. However, during an emergency, the UPS must provide an
         independent source of power to maintain such modes of communication systems as may be required
         to effectively manage an emergency situation when the main power system is unavailable.

         Typical uses of UPS power from communication systems include:
            satellite communications;
            radio systems;
            public address systems;
            general alarm systems;
            telephone exchanges;
            intercoms;
            DP alert lamps;
            diving alert.


5.4      UPS for Safety Related or Critical Systems

         UPSs or battery systems may be used to support the operation of safety related systems such as:
            fire detection systems;
            gas detection systems;
            ballast control systems;
            emergency shutdown systems;
            fire damper control panels;
            watertight door control panels;
            emergency riser disconnect systems.

         Some classification societies require isolation of UPS batteries during an emergency shutdown. Only
         UPSs for certain applications and in certain locations must have their batteries isolated and the reader
         is directed to the appropriate classification society rules for details.


5.5      UPS for Emergency Systems

         There are definitions of emergency systems in classification society rules, SOLAS and related
         publications. These specify the minimum amount of time for which certain emergency functions must
         be available when the main power system is unavailable. The size of many of these functions, such as
         bilge and fire pump, require the emergency generator to be running but other functions may be
         supported by a UPS at least in the short time it takes the emergency generator to start and connect.


5.6      DC Supplies with Battery Backup – Application to Generation Systems

         Generation systems application: The generation systems can be sub-divided into six basic systems.
            diesel engines;
            governors;
            automatic voltage regulators (AVR);
            switchgear control;
            protection;
            metering internal and external.



IMCA M 196                                                                                                     21
     Diesel engines: Diesel engine auxiliary supplies are normally 24V DC or 110V DC with 24V DC
     being the most common supply voltage. The loss of auxiliary supply will result in loss of engine
     control systems and the engine may shut down with inter-trip interface to the DG breaker. In other
     installations, the engine may continue to run with alarm to reduced protection.

     Governors: Governor auxiliary supplies are normally 24V DC but some electric governors require a
     40V DC supply to the actuator. The loss of auxiliary supply normally results in loss of governor
     control systems and therefore engine speed reduction with inter-trip interface to the DG breaker.

     Automatic voltage regulators (AVR): Auxiliary supplies for AVRs are normally 24V DC or 110V
     DC. The loss of auxiliary supply can result in failure of the AVR and therefore alternator excitation.
     AVRs can be categorised into five sub-divisions depending on how auxiliary supplies are utilised:
        analogue AVRs with no requirement for external DC supplies; this type of AVR normally utilises
         the DC supply system from the PMG and/or generator VT supply to provide the interface
         capability to trip the AVR;
        analogue AVRs with a requirement for external DC supplies; this type of AVR normally utilises
         24V DC or 110V DC to provide the interface capability to trip the AVR;
        digital AVRs with no requirement for external DC supplies; this type of AVR normally utilises the
         AC supply system from the PMG and / or generator VT supply to provide the interface capability
         to trip the AVR;
        digital AVRs with a requirement for external DC supplies; this type of AVR normally utilises 24V
         DC or 110V DC to provide the display, control and field build up power. The same supply is also
         used to provide the interface capability to trip the AVR.

     Switchgear control: The control of the switchgear consists of breaker close, open, under-voltage,
     locking magnet coils, etc. The control circuits may be relay logic control or PLC control within a
     multipurpose protection and control device or a combination of both. The auxiliary supplies are
     normally 24V DC or 110V DC with the latter being the most common supply voltage. The loss of the
     control auxiliary supply normally results in the circuit breaker being unable to trip as the majority of
     switchgear breakers do not have DC under voltage coils

     Protection: Protection devices can be arranged as a series of dedicated protection relays or a
     multipurpose protection and control device or a combination of both. Auxiliary supplies are normally
     24V DC or 110V DC with the latter being the most common supply voltage. The loss of the control
     auxiliary supply normally results in the protection systems failing as set; however, it is not uncommon
     for a trip output to be given on restoration of auxiliary supplies. The supply is normally the same
     supply as used for the breaker and metering control.

     Metering internal: Internal metering is normally supplied from transducers which have the same
     supply as the protection and control equipment. It is also becoming common for the metering to be
     supplied from the multipurpose control and protection device.

     Metering external: External metering is normally supplied from transducers which have the same
     supply as the protection and control equipment. It some instances, the metering may be supplied
     from the multipurpose control and protection device.

     Effects of auxiliary supply failures: The effects of auxiliary supply system failures should be
     analysed to ensure that a dangerous condition does not develop. This may require allocation of
     certain equipment to different auxiliary supplies. The following basic rules can be applied:
        Engines, governors and AVRs should not be supplied from the same auxiliary supply as the circuit
         breaker controls. If the generator circuit breaker cannot trip because of auxiliary supply system
         failure, a large active and reactive condition could develop which may damage the alternator
         and/or diesel engine.
        The external metering should not be supplied from the same auxiliary supply as the circuit
         breaker controls/protection relays.      Auxiliary power failure could result in the power
         management system not knowing the power available from connected generators and being
         unable to trip the main circuit breaker.
        As the majority of main generator circuit breakers have only a shunt trip coil, these should be
         supervised to ensure trip circuit integrity and advise the management system to request the
         operator to remove the generator from the system using the mechanical trip facilities.

22                                                                                                 IMCA M 196
6     Integration into Vessel Systems

6.1      Electrical Considerations

         There are three basic considerations:
            Input power – can the UPS operate successfully from the power system to which it is to be
             connected?
            Duration of independent operations – What stored energy capacity is required? – Typically,
             30 minutes at full load but this may be very application specific.
            Output power – Is the quality and quantity of the power the UPS delivers adequate for all
             operating conditions and modes of operation including the ability to deliver sufficient fault current
             to ensure selectivity?

         When answering the questions raised above, it may be useful to consider three characteristics of UPSs
         and their loads:
            Power factor: This is the ratio of the real (kW) power consumed by a load to the apparent
             (kVA) power. Loads associated with computer systems can have a poor power factor created by
             the use of switched mode power supplies.
            Crest factor: This is the ratio of the peak current to the RMS current drawn by a load. Many
             loads associated with computer equipment draw non-linear current from the supply. The result
             of this is that the UPS may have to deliver current peaks well in excess of the RMS current rating
             of the load.
            Surge factor: Many loads have an inrush current or starting current demand. The UPS must be
             capable of delivering the necessary current surge.

         Once again, it is important to note that the design of commercial UPSs for shore-based use is based
         on certain assumptions about the nature of the loads that will be supplied. Manufacturers of quality
         products will allow adequate margins for the factors discussed above in the design of their UPSs.
         However, for marine applications, it may not be acceptable to rely on these margins when specifying a
         UPS and the requirements of the actual loads to be supplied should be confirmed and discussed with
         the UPS supplier.


6.2      Run Time

         Figure 11 shows how the UPS run time (determined by the battery endurance) varies with the load on
         the UPS. The data in Figure 11 is based on the performance of a 3kVA online UPS from a major US
         manufacturer. The relationship between load and run time is highly non-linear but when the UPS is
         loaded to practical values (75%), the relationship between load and run time is approximately linear
         over about the top 50% of its range. Three battery arrangements are shown. Trace 1 shows the
         endurance of the UPS with the standard battery pack. Traces 2 and 3 show how the addition of extra
         batteries increases the run time. As Figure 12 shows, this UPS would not provide the 30 minute run
         time required for DP Class 2 and 3 vessels at 75% loading as it is only capable of 20 minutes at this
         load. Adding a second battery pack increases the 75% load run time to 80 minutes which should allow
         some margin for additional loads being added and battery ageing.




IMCA M 196                                                                                                      23
                                                                                                     75% Load




                                3

                           2

                   1


                       Figure 11 – Load against run time for 3kVA, 2100W online UPS




                   1                                      2                                  3
                                                                                                   75% Load




                            DP 2 & 3
                Figure 12 – Load against run time for 3kVA, 2100W online UPS (expanded)

     Figure 13 shows the relationship between apparent power and run time for a unity power factor load
     and a load with 0.7 power factor (also taken from manufacturer’s data). As might be expected, the
     load with the poor power factor has a longer endurance because, for the same apparent power (VA),
     it is consuming less energy (kW). By comparing a few points on the graph it is possible to show that
     the run time is largely determined by the real power consumed in each case (e.g. 1000VA is equivalent
     to 700W with a 0.7 pf and 53 minutes). The important consideration with poor power factor is that


24                                                                                               IMCA M 196
         the VA rating of the UPS cannot be exceeded even if the real power consumed is well below the UPSs
         rating.




                                      2


                           1

         700W




                                  Figure 13 – Effect of power factor on run time


6.3      Harmonics

         Power system harmonics can be a significant problem on vessels with large non-linear power
         electronic loads such as variable speed drives for thrusters, drilling, pipelaying and cranes. In simple
         terms, harmonics can be described as unwanted distortions in the power system voltage and current
         waveforms which can cause premature failure of major components and malfunction of control
         systems. There are several approaches to minimising the effects of harmonics including supplying
         sensitive equipment from UPSs but UPSs themselves are not entirely immune to the worst effects of
         harmonic distortions. Although classification societies set limits, levels of harmonics in marine power
         systems can be much higher than that allowed by shore-based utilities. Commercial UPSs generally
         have filters designed to reduce the effects of harmonics on loads. This is particularly necessary for
         standby UPSs because the load is supplied mostly from the main AC input. Similar filters can also be
         found in online UPSs which switch automatically to their bypass on fault or overload. Experience
         shows that these filters may not be able to cope with the level of harmonics found in marine systems
         and may burn out as a result. If the intended application requires the UPS to operate from a supply
         with a high harmonic content this requirement should be discussed with the UPS supplier.




IMCA M 196                                                                                                     25
                           Figure 14 – Harmonic distortion in 6.6kV supply voltage

      Online UPSs that use controlled rectifiers for battery charging may be badly affected by commutation
      notches on their input power supply which are associated with large 6 and 12 pulse drives used for
      drilling and thrusters. These notches may appear as false zero crossings causing the malfunction of the
      battery charger to the point where UPS batteries are not properly charged reducing the run-time in
      battery mode.


6.4   Interface Systems Considerations – Alarms and Monitoring

      Alarms: In order that UPSs can make a useful contribution to the safe and reliable operation of a
      vessel, they need to provide the vessel operator with a useful range of information about their
      condition and configuration. As a minimum, each UPS and DC power supply should have the
      following alarms:
         ‘On battery supply’ – This alarm should be designed to indicate that load current is being drawing
          from the batteries. Some UPSs only have a ‘main supply failed’ alarm which is useful but does not
          provide the same degree of security as actually monitoring the battery current.
         ‘Battery disconnected’ – This alarm indicates that the battery has become disconnected. Some
          classification societies also require an alarm to indicate that the battery protection has operated
          but this does not provide the same level of security as sensing the connection to the battery.
         ‘In bypass mode’ – This alarm should indicate whether the UPS is currently in manual or
          automatic bypass mode which may prevent it supplying the load during a blackout.

      Monitoring: Modern UPSs can provide a large amount of information on their own status and
      performance. Limited information can be accessed by way of dry-contact relays in some applications.
      Much more can be obtained by way of serial communication links.


6.5   Dual Supplies to UPSs

      It is common practice to provide UPSs used as part of the vessel’s control and automation system
      with a main and a backup supply by way of either a manual or automatic changeover switch as shown
      in Figure 26. Typically, the normal supply comes from the main power systems and the backup supply
      is from the emergency power systems. For DP vessels, class may require that the normal supply is the
      main power system. However, it is useful for black ship start, lay-up, etc. if the UPS batteries can be
      charged from the emergency generator. It can also offer a degree of protection against a premature
      battery failure if the UPS automatically changes over to the supply from the emergency generator as

26                                                                                                  IMCA M 196
         soon as it becomes available. However, as with any connection between systems, care must be taken
         to design the changeover switch so that it will not transfer a fault which risks causing a blackout or
         severe voltage dip on both sources of supply if the UPS or changeover switch is faulty.


6.6      ESD Requirements

         Some classification societies may require that UPS batteries are disconnected on activation of certain
         levels of the emergency shutdown system (ESD). DNV have advised NDC that the requirement for
         shutdown of UPSs in its rules is related to abandon platform shutdown/abandon vessel shutdown on a
         mobile offshore unit. The origin of the requirement is in the DNV Offshore Rules 2008, DNV-OS-
         A101, Figure 1. This figure lists, among other things, which systems can remain active after initiation
         of such a shutdown level (UPSs are not included in this list). There are exceptions to this requirement
         related to mobile offshore drilling units (MODUs) which must, as a minimum, comply with IMO
         MODU Code Sec. 6.5. ‘In all cases the UPSs and location of such shall comply with the requirements
         of DNV-OS-A101 Sec.5 F104 which state that:

         ‘Uncertified (Ex) electrical equipment may be left operational after ESD or gas detection affecting its area of
         location, provided that the ventilation to the room where the equipment is located is efficiently isolated. Typical
         living quarter design will meet this requirement, other enclosed spaces will be specially considered.’

         There are at least two important issues associated with this requirement:
            UPSs must be supplied with a means to disconnect the UPS batteries remotely.
            Any UPS required for propulsion or vessel control should be able to start and provide AC power
             from its batteries without the main input supply being present. This feature is important to allow
             the vessel to be ‘black started’ quickly and efficiently if the ESD is cancelled or after periodic
             testing of the ESD. This may seem like an obvious function but UPSs have been designed that
             cannot do this.


6.7      UPS Systems DC Power Supplies – Fault Levels and Protection Discrimination

         Fault level calculations: Classification societies require that converters used as power supplies
         (which includes UPSs) should be able to provide enough fault current to operate over current
         protection selectively. Calculations should be carried out to determine the fault levels of the system.
         The fault level study should be inclusive of the battery bank, charger and or inverter contributions,
         where appropriate, but most commercial UPSs used in marine applications appear to transfer faults to
         their bypass. The impedance of filters and other line conditioning equipment may have a significant
         effect on fault current levels.

         Voltage decrement: The voltage drop and duration under fault conditions should be calculated if it
         is intended that consumers should be able to ride-through the disturbance associated with clearing a
         ‘branch’ fault.

         Protection co-ordination: The protection system, i.e. fuses, MCBs and electronic protection
         devices within the chargers and or inverters should be considered. Fault level discrimination is
         generally not given a great deal of consideration in small power systems, including UPSs, and the focus
         is generally on ensuring safety rather than continuity of supply.


6.8      Dual Voltage UPSs

         One arrangement that may present problems, if not carefully considered, is the dual voltage UPS. It is
         often the case that marine power plants require 220V AC and 24V DC supplies with battery backup
         for control applications and these units may be provided by shipyards as a cost effective solution. In
         some cases these units are created by connecting a 24V DC power supply onto the output of the
         220V AC UPS such that the batteries in the AC UPS provide the battery backup for both voltages.
         The difficulty with this arrangement arises when a fault occurs in the 24V DC distribution and the DC
         power supply does not have sufficient fault capability to operate the over-current protection
         selectively. The problem can be overcome by providing battery backup at the 24V DC level to
         provide the necessary fault current but this may be no more cost effective than providing a separate
         24V DC system with its own battery bank. If the number of DC consumers is small, providing a 24V
         DC power supply off the UPS for each consumer is a possible alternative.

IMCA M 196                                                                                                                27
6.9   Common/Summary Alarm

      It is tempting to route all UPS alarms into a single common or summary alarm to save I/O. However,
      care must be taken to distinguish minor events from more serious conditions. Most UPSs provide an
      audible alarm indicating that the battery is in discharge. This is a useful feature to provide a quick
      confirmation. The following alarms should be separate:
         Battery in discharge – Time on UPS is limited.
         UPS in bypass mode – System is not properly configured.
         A ‘common’ UPS fault alarm may be used to indicate other conditions.

      It is important to discuss alarm requirements with manufacturers prior to purchase and ascertain
      whether the unit can be made application specific.




28                                                                                                 IMCA M 196
7     Strategies for UPS and DC Distribution

7.1      General

         The provision of UPS power to consumers is an important issue on any type of vessel but it is
         particularly important on vessels where the power plant or control systems must be fault tolerant.
         Typical applications include vessels with class notation for redundant propulsion or DP. There is a
         surprisingly common misconception that by supplying critical equipment from a UPS it can be
         considered not to fail. This is not correct. A UPS and its loads should be considered to fail like any
         other piece of electronic equipment.

         Distribution strategies may be described as centralised, distributed or hybrid solutions with elements
         of both approaches but, whatever strategy is adopted, it should support the redundancy concept.
         Those elements of a propulsion system that typically require UPS power include:
            vessel control systems including power management and DP;
            power generation systems including engines and their auxiliary systems;
            power distribution systems;
            thrusters and steering gear.

         The propulsion arrangement shown in Figure 15 is not particularly important but could represent a
         large DP Class 2 ROV support vessel or a medium sized pipelayer. The principles under discussion
         apply equally to any other arrangements including propulsion systems for DP semi submersibles.

                                                                                                      THRUSTERS AND
                                        CONTROL              ENGINES AND       POWER DISTRIBUTION
                                                                                                    PROPULSION SYSTEMS
                                        SYSTEMS            AUXILIARY SYSTEMS       SYSTEMS
                                                                                                      STEERING GEAR




                                                                                                                         T5

                                                                       G1
                                             CONTROL                                                                          R1
                                              SYSTEM
                                                 A                     G2        SWBD
                                        T3                                                            T4
                T1        T2                                           G3


                                                                       G4

                                                                                                                         T6
                                                                       G5        SWBD

                                                                                                                              R2
                                                                       G6
                                             CONTROL
                                              SYSTEM
                                                 B




                                   FIELD STATION OR CONTROL SYSTEM




                         Figure 15 – Parts of a redundant propulsion system requiring UPS


7.2      Minimum Requirement

         For a vessel with a simple two way split in its redundant propulsion system (such as that shown in
         Figure 15) all that is required for fault tolerance are two main UPSs each with a distribution system
         supplying the appropriate parts of the propulsion system such that failure of either UPS does not
         cause the loss of more machinery than the vessel’s worst case failure design intent (WCFDI). In other
         words, if one UPS fails, the vessel should be able to hold position using the surviving propulsion and
         control system equipment. Note that automatic bypasses in UPSs cannot be considered as
         contributing to redundancy because there is always a possibility that the static switch or some part of
         the distribution systems might fail. Although Figure 16 shows the minimum requirement for fault
         tolerance, classification societies may require additional features such as emergency supplies to
         steering gear.

         Variations on this simple arrangement may include providing a ‘backup’ raw supply to control systems
         by way of local auto changeovers or providing individual internal battery backup in control systems

IMCA M 196                                                                                                                         29
     where the AC power is converted to low voltage DC. Note that introducing changeovers into any
     redundancy concept introduces other risks and needs very careful consideration. It is often the case
     that UPS power distributed at 220V AC or 110V AC is transformed and rectified to 24V DC at each
     consumer. The argument for not distributing DC directly throughout the vessel is related to the large
     cable size required to distribute 24V DC without unacceptable voltage drop.

     A more common and more practical UPS distribution arrangement for larger vessels is shown in
     Figure 17. This arrangement introduces an additional fore-aft split into the port-starboard split
     required for redundancy. This four-way split does not improve the vessel’s overall worst case failure
     which is still determined by the two way split in the power generation system but does reduce the
     impact of a UPS failure and leaves the vessel with greater manoeuvring capability. The main reason for
     further subdivision of this type is to reduce the length of cable runs and site UPS distribution boards
     closer to the equipment they supply.

       UPS A




                                                                                                                 T5

                                                                    G1
                                            CONTROL                                                                        R1
                                             SYSTEM
                                                A                   G2           SWBD
                                       T3                                                               T4
               T1      T2                                           G3


                                                                    G4

                                                                                                                 T6
                                                                    G5           SWBD

                                                                                                                           R2
                                                                    G6
                                            CONTROL
                                             SYSTEM
                                                B




       UPS B




                                  FIELD STATION OR CONTROL SYSTEM        INDICATES SPLIT IN REDUNDANCY CONCEPT




                            Figure 16 – Minimum requirements for UPS distribution




30                                                                                                                    IMCA M 196
             UPS A                                                                                                          UPS C




                                                                                                                       T5

                                                                          G1
                                                  CONTROL                                                                       R1
                                                   SYSTEM
                                                      A                   G2           SWBD
                                             T3                                                               T4
                     T1       T2                                          G3


                                                                          G4

                                                                                                                       T6
                                                                          G5           SWBD

                                                                                                                                R2
                                                                          G6
                                                  CONTROL
                                                   SYSTEM
                                                      B




             UPS B                                                                                                          UPS D




                                        FIELD STATION OR CONTROL SYSTEM        INDICATES SPLIT IN REDUNDANCY CONCEPT




                     Figure 17 – More practical UPS distribution with port/starboard and fore/aft split


7.3      Distributed UPS Arrangement

         An increasing number of designers now take the view that a distributed UPS strategy offers the best
         solution. Some even go so far as to specify that if a particular vendor’s equipment requires UPS
         power then a suitable UPS should be included with the equipment such that it can be supplied with
         raw power from the vessel’s power distribution scheme.

         The distributed approach has advantages for vessels with a multi-way split in their redundancy
         concepts where it is necessary to reduce the impact of the worst case failure to a single engine or
         thruster. However, if each manufacturer provides a UPS for each piece of equipment that is
         redundant with respect to any other then there may be a very large number of different types of UPSs
         all with different batteries which will need testing, maintenance and replacement as shown in Figure
         18. A compromise would involve grouping together equipment which serves a single engine or
         thruster and supplying all of that equipment from a single UPS. This provides the necessary level of
         independence between redundant elements and reduces the number of UPS units required but great
         care should be taken not to common up supplies for protection systems and control systems. For
         example, if an AVR, governor and generator protection relay are supplied from the same source, the
         protection relay will not be able to trip the generator on detection of an AVR or governor fault.
         If this arrangement cannot be avoided then loss of UPS power must initiate the tripping action by way
         of a backup supply. It is also preferable to separate control and alarm functions but the advent of
         distributed vessel management systems means that these functions are generally provided by a
         common field station so the UPS does not introduce any more commonality. Figure 19 shows how
         this might be achieved for a variable speed thruster. Providing UPS power to several different
         vendors’ equipment does require more integration engineering than if the vendors supply their own
         UPSs.

         The distributed approach also has advantages for DP Class 3 designs where there is a need to reduce
         the risk of transfer of fault associated with fire and flood in one compartment. The strategy of closely
         associating a UPS with groups of equipment related to one redundant element of the design fits in well
         with the compartmentalisation scheme for DP Class 3 vessels.




IMCA M 196                                                                                                                           31
                                                                            24Vdc           110Vdc
                                   A                      C         E                                 G                    I         K
                                                                              A               A




                                                                                                                                     T5

                                                                                G1
                                                    CONTROL                                                                                             R1
                                                     SYSTEM
                                                        A                       G2           SWBD
                                               T3                                                                  T4
                   T1       T2                                                  G3


                                                                                G4

                                                                                                                                     T6
                                                                                G5           SWBD

                                                                                                                                                        R2
                                                                                G6
                                                    CONTROL
                                                     SYSTEM
                                                        B




                                                                            24Vdc           110Vdc
                        B                      D          F         H                                 J                               L
                                                                              B               B




                                          FIELD STATION OR CONTROL SYSTEM




                                                Figure 18 – Distributed UPS scheme

       AUXILIARY
                                 UPS
        POWER


                                                      )


                                                                                        VESSEL             THRUSTER              THRUSTER
                                                                                     MANAGEMENT            CONTROL                CONTROL
                                                                                     FIELD STATION           UNIT              FIELD STATION
                                             ) ) ) ) ) )
                                                                                     THRUSTER BILGE       THRUSTER             STEERING CONTROL & FEEDBACK
                                                                                     VENTILATION          MANUFACTURER’S       SPEED CONTROL AND & FEEBACK
                                                                                     ALARMS               CONTROL SYSTEM       STEERING PUMP ON/OFF
                                                                                                                               LUBE OIL PUMP ON/OFF
                                                                                                                               DRAIN PUMP ON/OFF

                             DE-IONISED
                               WATER
                              COOLING
                                UNIT




                                                                                                             MCC/USB FOR
            MAIN
                                             VSD                        MOTOR                                 THRUSTER
           POWER
                                                                                                             AUXILIARIES

                                                                                              THRUSTER      HYDRAULIC PUMPS VSD
                                                                                                            DRAIN PUMP STARTER
                                                                                                            LUBE OIL STARTER



                                 Figure 19 – Grouping UPS consumers for a single thruster


7.4   Centralised UPS Systems

      There is still strong support amongst some designers for large centralised UPS schemes. The
      advantages are related to the perceived higher quality and reliability of large UPS systems. In such a
      scheme, there is generally only one type of UPS manufacturer and one type of battery to be
      considered in maintenance programmes. This is a worthwhile consideration in any UPS scheme.

      In DP vessels with multi way splits and low impact worst case failure design philosophies, a centralised
      approach results in an arrangement like that shown in Figure 20 in which each piece of equipment
      requiring UPS power receives a supply from two large centralised UPSs. Although it is possible to
      arrange for UPSs to run in synchronism with each other and load share, the normal way in which dual
      supplies from UPSs are made common within equipment is by rectifying and conversion to low voltage
      DC such as 24V DC. In other cases a mechanical auto-changeover is provided particularly if AC
      power is required. The mechanical changeover does not provide continuity of supply on UPS failure
      and so the redundancy concept should accept that the equipment may have to be restarted on failure

32                                                                                                                                               IMCA M 196
         of one UPS. Where auto-changeovers are used, it is important that they cannot transfer a fault from
         one supply to another. It should also be possible to monitor which supply they are connected to and
         that the backup supply is present to increase confidence that the equipment will be available after a
         fault and that equipment is distributed evenly between the two supplies so that it is not necessary for
         everything to changeover on loss of one UPS.

         It may be very difficult to make redundant centralised UPS schemes comply with the DP Class 3
         requirements of some Classification Societies. Requirements in IMO MSC 645 to prevent transfer of
         fault can be interpreted as meaning that supplies originating from power systems intended to provide
         redundancy cannot enter the same fire subdivision or watertight compartment even if they serve the
         same piece of equipment (if both are live at the same time). If it is intended to implement a
         centralised redundant UPS scheme on a DP Class 3 design then the concept should be discussed with
         the classification society at an early stage in the design process.

             UPS A




                                                                                               T5

                                                                      G1
                                              CONTROL                                                       R1
                                               SYSTEM
                                                  A                   G2   SWBD
                                         T3                                         T4
                     T1    T2                                         G3


                                                                      G4

                                                                                               T6
                                                                      G5   SWBD

                                                                                                            R2
                                                                      G6
                                              CONTROL
                                               SYSTEM
                                                  B




             UPS B




                                    FIELD STATION OR CONTROL SYSTEM




                                  Figure 20 – Centralised redundant UPS scheme

7.5          Backup UPS

         A variation on the simple two or four UPS scheme described in Figure 16 and Figure 17 is shown in
         Figure 21. In this arrangement, UPSs A and B are designed to transfer to UPS C on detection of
         inverter failure rather than their backup supply. This arrangement does not improve the overall worst
         case failure which is still determined by the two-way split in the UPS power distribution scheme.
         However, it recognises the fact that UPSs have a finite reliability and losing one of the two UPSs is
         more likely than losing the entire distribution scheme. Losing one of the two UPSs shown in Figure 16
         severely disables the vessel to the point where position critical operations would have to be
         terminated until the UPS can be repaired. By providing a backup UPS (UPS C) as shown in Figure 21,
         operations can continue without interruption while the faulty UPS is repaired. Static switches are
         generally used to create the changeover.

         As UPS C forms a common point between the two distribution systems, care should be taken to
         ensure that a fault in UPS C cannot affect the operation of both UPS A and UPS B. As some UPSs
         transfer load to their auto-bypass to operate over-current protection, some thought would have to be
         given to ensuring that over-current protection operates effectively when the bypass mode is effectively
         a second UPS.



IMCA M 196                                                                                                       33
       MAIN SWITCHBOARD A             EMERGENCY SWITCHBOARD                 MAIN SWITCHBOARD B



                  )                                  )                                 )



               UPS A                             UPS C                             UPS B




                STATIC                                                           STATIC
                SWITCH                                                           SWITCH




                 UPS                                                              UPS
             DISTRIBUTION                                                     DISTRIBUTION

                                        Figure 21 – Backup UPS


7.6   Strategies for DC Power Supply Distribution

      The same principles that have been discussed for UPS distribution can also be applied to DC power
      supplies. Typically, a traditional approach is taken to the provision of DC power for switchboards
      with a dedicated DC power supply for each switchboard or bus section. DC power for engine
      controls can be split along the lines of the overall split in the redundancy concept with groups of
      engines sharing a common power supply. Because of the ease with which DC power supplies can be
      tied together through diodes, it is quite common to find dual DC supplies to consumers. This practice
      introduces additional commonality between otherwise redundant elements of a propulsion system and
      great care must be taken not to provide paths for fault transfer. Some designers prefer to use DC to
      DC converters rather than diodes as this provides isolation of earth faults and some additional
      impedance in relation to fault transfer. Other designers prefer to provide a dedicated DC power
      supply for each consumer.


7.7   Cross Connection of DC Power Supplies

      Direct current power supplies: Cross connections tend to be a feature of DC power systems as
      these supplies are easy to cross connect using diodes or DC to DC converters. Unfortunately, a
      short circuit fault at the common point causes a voltage dip on both power supplies and generator or
      thruster circuit breakers may trip before control system fuses or MCBs operate to clear the fault.
      Such failures are not often simulated at FMEA proving trials due to concerns over equipment damage.
      On occasions when such systems have been tested realistically, thrusters have tripped. See Figure 22,
      Figure 23 and Figure 24.




34                                                                                                IMCA M 196
                                                              This arrangement meets Class but may
                     DC                                                                                                                     DC
                   Supply A
                                                              not be sufficiently reliable if generators                                  Supply B
                                                              stop on loss of control voltage.




                   Control voltage bus for generators 1, 2 and 3                                      Control voltage bus for generators 4, 5 and 6



                                           Figure 22 – Single supply for each main switchboard



                                                             This arrangement apparently improves
                     DC                                      reliability but introduces a common cause                                   DC
                   Supply A                                  failure as a fault on either bus can cause                                Supply B
                                                             the voltage on supplies A & B to dip far
                                                             enough to cause generators to trip.




                   Control voltage bus for generators 1, 2 and 3                                   Control voltage bus for generators 4, 5 and 6


                                         Figure 23 – Main switchboard supplies cross-connected



                                                     This arrangement provides the required
               DC                      DC                                                                    DC                      DC
             Supply A                Supply B        improvement      in     reliability and               Supply C                Supply D
                                                     maintainability without introducing the
                                                     common cause failure.




             Control voltage bus for generators 1, 2 and 3                                      Control voltage bus for generators 4, 5 and 6


                                            Figure 24 – Dual supply for each main switchboard

         Note that some classification societies require that there is a cross-over arrangement to allow either
         DC power supply to provide power to for either control bus. This can be a manual selector and
         remain isolated for normal operations.




IMCA M 196                                                                                                                                            35
8     Class Requirements for UPS, DC Supplies and Batteries

8.1      General

         Classification societies have rules concerning the design, location and installation of UPSs and DC
         supplies for various supplies. The table which follows Section 8.3 lists the main requirements.

         Rules for the location of batteries of different types and sizes in specialised compartment have been
         omitted as these are detailed and extensive and the reader is directed to the rules of the classification
         society in this case. Rules which apply to engine starting batteries are also omitted as not directly
         relevant to UPS or DC supply batteries. The wording of some rules has been paraphrased in some
         cases.

         The purpose of the table is only to give an indication of the range of issues that must be considered to
         meet class requirements. In all cases, the reader should consult the appropriate year of the
         classification societies’ rules.

         The table has been developed from the following rules:
            DNV Rules for Ships –Part 4 Chapter 8 January 2008 – ‘Electrical Installations’.
            DNV Offshore Standard DNV-OS-D201, January 2008– ‘Electrical Installations’.
            DNV Offshore Standard DNV-OS-A101, October 2005-‘Safety Principles and Arrangements’
             (latest at time of writing).
            ABS Rules for Building and Classing Steel Vessels 2008.
            ABS Rules Effects of Harmonics 2006.
            Lloyd’s Register of Shipping, Rules and Regulations for the Classification of Ships – 2006.
            Germanischer Lloyd, ‘Rules & Guidelines 2008, Rules for Classification and Construction’, I - Ship
             Technology, Part 1 - Seagoing Ships, Chapter 3 - Electrical Installations.


8.2      Common Requirements

         As can be seen from the table below, there is some commonality between classification society
         requirements for UPSs. In particular, a battery endurance of 30 minutes is required by all four
         classification societies listed. There is also significant agreement on the types of alarms to be provided
         for a UPS.


8.3      Standards Organisations

         In addition to classification society rules, the following international and US standards are applicable to
         UPSs and may be useful in the preparation of vessel specifications, etc.
            IEC 62040 from which is derived BS EN 62040-3:2001 ‘Uninterruptible Power Systems (UPS)’.
            NEMA Standards Publication PE 1-2003 ‘Uninterruptible Power Systems (UPS) – Specification and
             Performance Verification’.
            IEEE Std 450-2002 IEEE Recommended Practice for Maintenance, Testing and Replacement of
             Vented Lead-Acid Batteries for Stationary Applications’.
            IEEE Std 1188 -2005, IEEE Recommended Practice for Maintenance Testing and Replacement of
             Valve-Regulated Lead Acid (VRA) Batteries for stationary applications’.
            IEEE Std 1184 -2006, ‘IEEE Guide for Batteries for Uninterruptible Power Supply Systems’.




36                                                                                                         IMCA M 196
                                                                                                                         Rule Requirement
                    Design Issue
IMCA M 196




                                                              DNV                                    Lloyd’s Register                                ABS                                Germanischer Lloyd
             Battery
                                            Minimum of 30 mins following loss of         Minimum of 30 mins following loss of       Minimum of 30 mins following loss of       Minimum of 30 mins following loss of
             Capacity
                                            main supply                                  main supply                                main supply                                main supply
                                                                                         Voltage tolerance:15% to +30% of
             DC battery supply voltage                                                   nominal DC system voltage
             variations                                                                  Voltage cyclic variation: max 5%
                                                                                         Voltage ripple: max 10%
                                            Circuits connected to batteries above        Circuits connected to batteries above
                                            12V or above 1 Ah capacity shall have        12V or 1Ah shall have short circuit and
                                            short circuit and over-current               over current protection.
                                            protection.                                  Protection for battery circuits is to be
                                            Protection may also be required for          provided at a position external and
                                            smaller batteries capable of creating a      adjacent to the battery compartments.
                                            fire risk.
                                            Short circuit protection shall be located
             Battery protection             as close as is practical to the batteries,
                                            but not inside battery rooms, lockers,
                                            boxes or close to ventilation holes.
                                            The connection between the battery
                                            and the charger is also to have short
                                            circuit protection.
                                            Connections between cells and from
                                            poles to first short circuit protection
                                            shall be short circuit proof.
                                            Where the emergency source of                Carrying the emergency electrical load     Carrying the emergency electrical load
                                            electrical power is an accumulator           without recharging while maintaining       without recharging while maintaining
                                            battery it shall be capable of carrying      the voltage of the battery throughout      the voltage of the battery throughout
                                            the emergency electrical load without        the discharge period within 12% above      the discharge period within 12% above
             Where the emergency            recharging while maintaining the voltage     or below its nominal voltage.              or below its nominal voltage.
             source of electrical power     of the battery as required by A200.          Automatically connecting to the            Automatically connecting to the
             is an accumulator battery it   (Interpretation of SOLAS Ch. II-             emergency switchboard in the event of      emergency switchboard in the event of
             is to be capable of:           1/43.3.2.1)                                  failure of the main source of electrical   failure of the main source of electrical
                                                                                         power                                      power
                                                                                         Immediately supplying at least the         Immediately supplying at least the
                                                                                         essential services.                        essential services.
37
                                                                                                                     Rule Requirement
                    Design Issue
38




                                                       DNV                                    Lloyd’s Register                                    ABS                       Germanischer Lloyd
                                     Each charging device is, at least, to have   Where a reserve source of energy             The charging facilities are to be such
                                     sufficient rating for recharging to 80%      consists of a rechargeable accumulator       that the completely discharged battery
                                     capacity within 10 hours, while the          battery a means of automatically             can be recharged to 80% capacity in not
             Battery charging rate   system has normal load.                      charging the batteries is to be provided     more than 10 hours.
                                                                                  which is to be capable of recharging
                                                                                  them to minimum capacity
                                                                                  requirements within 10 hours.
                                     The emergency source of power shall          No accumulator battery except for            The emergency switchboard is to be
                                     be located above the uppermost               engine starting, is to be installed in the   installed as near as is practicable to the
                                     continuous deck and be readily               same space as the emergency                  emergency source of electrical power.
                                     accessible from open deck. It shall not      switchboard.                                 No accumulator battery is to be
                                     be located forward of the collision                                                       installed in the same space as the
                                     bulkhead.                                                                                 emergency switchboard. An indicator
                                     The emergency source of power shall                                                       is to be mounted on the main
             Location
                                     be automatically connected to the                                                         switchboard or in the machinery
                                     emergency switchboard in case of                                                          control room to indicate when these
                                     failure of the main source of electric                                                    batteries are being discharged.
                                     power.
                                     The emergency switchboard shall be
                                     installed as near as is practicable to the
                                     emergency source of electrical power.
             General
                                     UPS or battery systems for operation
                                     of the main power distribution shall not
                                     be located together with equipment
             Location
                                     necessary for the operation of the
                                     emergency power generation or
                                     distribution or vice versa
IMCA M 196
                                                                                                                Rule Requirement
                    Design Issue
IMCA M 196




                                                       DNV                                 Lloyd’s Register                        ABS            Germanischer Lloyd
                                                                               Signboards shall be fitted in battery
                                                                               rooms and on doors or covers of
                                                                               boxes or lockers, warning against risk
                                                                               for explosive gas, smoking and the use
                                                                               of naked lights.
                                                                               All batteries shall be provided with
                                                                               labels (nameplates) of flame retardant
                                                                               material, giving information on the
             Signs and markings                                                application for which the battery is
                                                                               intended, make, type, voltage and
                                                                               capacity. Instructions shall be fitted
                                                                               either at the battery or at the charging
                                                                               device, giving information on
                                                                               maintenance and charging.
                                                                               Battery systems above 50V shall be
                                                                               marked with special visible warning
                                                                               signboard, i.e. ‘Warning xxx voltage’.
             UPS
                                       For Converters servicing as power                                                                 UPS units are to be constructed in
                                       supplies for emergency power external                                                             accordance with IEC 62040, or an
                                       bypass arrangements shall be provided                                                             acceptable and relevant national or
                                                                                                                                         international standard.
                                                                                                                                         A bypass or a second UPS in parallel is
                                                                                                                                         to be provided.
                                                                                                                                         The operation of the UPS is not to
                                                                                                                                         depend upon external services.
                                                                                                                                         The UPS unit is to be monitored. An
             Design and construction                                                                                                     audible and visual alarm is to be given
                                                                                                                                         on the ship’s alarm system for
                                                                                                                                         power supply failure (voltage and
                                                                                                                                         frequency) to the connected load,
                                                                                                                                         earth fault, if applicable,
                                                                                                                                         operation of battery protective device -
                                                                                                                                          when the battery is being
                                                                                                                                         discharged, and
                                                                                                                                         when the UPS is not operating under
                                                                                                                                         normal condition.
39
                                                                                                          Rule Requirement
                    Design Issue
40




                                                             DNV                       Lloyd’s Register                              ABS                       Germanischer Lloyd
             Electrical Power Supply
             Power supply failure with     3 interruptions during 5 minutes
             successive power breaks       — switching-off time 30 s each case.
             with full power between
             breaks:
                                           combination of permanent frequency                                      combination of permanent frequency
                                           variations of ±5% and permanent                                         variations of ±5% and permanent
                                           voltage variations of +6/−10% of                                        voltage variations of +6/−10% of
             Power supply variations for   nominal                                                                 nominal
             equipment connected to        combination of frequency transients (5                                  combination of frequency transients (5
             AC systems:                   s duration)                                                             s duration)
                                           ±10% of nominal and voltage transients                                  ±10% of nominal and voltage transients
                                           (1.5 s duration)                                                        (1.5 s duration)
                                           ±20% of nominal.                                                        ±20% of nominal.
                                           voltage tolerance continuous ±10% of                                    voltage tolerance continuous ±10% of
             Power supply variations for   nominal                                                                 nominal
             equipment connected to        voltage transients cyclic variation 5% of                               voltage transients cyclic variation 5% of
             DC systems:                   nominal                                                                 nominal
                                           — voltage ripple 10%.                                                   — voltage ripple 10%.
                                           +30% to −25% for equipment                                              +30% to −25% for equipment
                                           connected to battery during charging                                    connected to battery during charging
             Power supply variations for
                                           +20% to −25% for equipment                                              — +20% to −25% for equipment
             equipment connected to
                                           connected to battery not being charged                                  connected to battery not being charged
             battery power sources:
                                           — voltage transients (up to 2 s
                                           duration) ±25% of nominal.
                                           Converters serving as power supplies
                                           shall be able to supply a short circuit
                                           current sufficient for selective tripping
                                           of down stream protection without
             Operation of protection
                                           suffering internal damage. Current
                                           limiting power supplies or power
                                           supplies limited by internal temperature
                                           may be used for single consumers.
IMCA M 196
                                                                                                       Rule Requirement
                    Design Issue
IMCA M 196




                                                          DNV                       Lloyd’s Register                      ABS   Germanischer Lloyd
             Standby Power Supply
                                        Battery or UPS power shall be
                                        provided as standby power for the
                                        following:
                                        Systems required to operate in a
                                        blackout
                                        Systems required to restore normal
             Requirements
                                        function after a blackout
                                        Special requirements
                                        Note a UPS alone shall not be regarded
                                        as providing redundancy when two
                                        mutually independent supplied are
                                        required. Once source may be a UPS.
             Switchboard Control Supplies from Battery Systems
                                        The control power can be supplied
             Sources of switchboard
                                        from a battery when the switchboard
             control power
                                        can be divided in two
             Number of sources of       An independent control power supply
             control power              must be provided for each bus section.
                                        Cross over facilities must be provided
                                        so that the battery system for each bus
             Cross over
                                        section can supply other the control
                                        power for other bus sections.
                                        Each battery system must have
                                        sufficient stored energy for two
                                        operations of all the components
                                        connected to that section of
             Number of operations
                                        switchboard. In the case of switching
             from battery source
                                        off circuit breakers, it must be possible
                                        to trip all circuit breakers
                                        simultaneously without unacceptable
                                        voltage drop.
41
                                                                                                   Rule Requirement
                      Design Issue
42




                                                        DNV                     Lloyd’s Register                              ABS                                 Germanischer Lloyd
             Alarms
                                     An alarm shall be given at a manned                                    The battery charger unit or                 The UPS unit is to be monitored. An
                                     control stations if the charging of                                    uninterruptible power system (UPS)          audible & visual alarm is to be given on
                                     battery fails or if the battery is being                               unit is to be monitored and audible and     the ship’s alarm system when the
             Charging
                                     discharged.                                                            visual alarm is to be given in a normally   battery is being discharged.
                                                                                                            attended location for when the battery
                                                                                                            is being discharged.
             Input failure           An alarm shall be given when the input                                 The battery charger unit or                 The UPS unit is to be monitored. An
                                     power fails to a UPS                                                   uninterruptible power system (UPS)          audible and visual alarm is to be given
                                                                                                            unit is to be monitored and audible and     on the ship’s alarm system for power
                                                                                                            visual alarm is to be given in a normally   supply failure (voltage and frequency)
                                                                                                            attended location for power supply          to the connected load.
                                                                                                            failure (voltage and frequency) to the
                                                                                                            connected load.
             Earth fault             An alarm shall be given when there is                                  The battery charger unit or                 The UPS unit is to be monitored. An
                                     an earth fault                                                         uninterruptible power system (UPS)          audible and visual alarm is to be given
                                                                                                            unit is to be monitored and audible and     on the ship’s alarm system for earth
                                                                                                            visual alarm is to be given in a normally   fault.
                                                                                                            attended location for earth fault.
             Bypass                  An alarm shall be given when the UPS                                   The battery charger unit or                 The UPS unit is to be monitored. An
                                     bypass is in operation                                                 uninterruptible power system (UPS)          audible and visual alarm is to be given
                                                                                                            unit is to be monitored and audible and     on the ship’s alarm system when the
                                                                                                            visual alarm is to be given in a normally   UPS is not operating under normal
                                                                                                            attended location when the bypass is in     conditions.
                                                                                                            operation for on-line UPS units.
             Battery MCB             An alarm shall be given when the                                       The battery charger unit or                 The UPS unit is to be monitored. An
                                     battery protection has operated                                        uninterruptible power system (UPS)          audible and visual alarm is to be given
                                                                                                            unit is to be monitored and audible and     on the ship’s alarm system for
                                                                                                            visual alarm is to be given in a normally   operation of battery protective device.
                                                                                                            attended location for operation of
                                                                                                            battery protective device
IMCA M 196
                                                                                                       Rule Requirement
                    Design Issue
IMCA M 196




                                                            DNV                     Lloyd’s Register                             ABS                       Germanischer Lloyd
             Testing
             Testing of battery supplies   UPS systems and DC battery backup                                    Appropriate testing is to be carried out
                                           power systems shall be function tested                               to demonstrate that the battery
                                           for dip free voltage when feeding                                    charger units and uninterruptible
                                           power is turned off                                                  power system (UPS) units are suitable
                                                                                                                for the intended environment. This is
                                                                                                                expected to include as a minimum -
                                                                                                                functionality, including operation of
                                                                                                                alarms; temperature rise; ventilation
                                                                                                                rate and battery capacity.
             Capacity                      Battery systems shall be tested in
                                           battery supply mode for a period
                                           determined by the requirements of the
                                           system and the relevant rules.
             Independence                  When proving the independency for
                                           the main and emergency power
                                           systems the emergency system will be
                                           disconnected including batteries and
                                           UPSs. The following shall be tested
                                           black start and normal operation.
43
9     Switching Arrangements

9.1      General

         The UPS or DC power unit is often just one part of a wider power distribution scheme for battery
         backup power which may include:
            automatic or manual changeovers for dual supplies to the input of the UPS;
            changeovers at consumers;
            external manual bypasses direct to the UPS distribution.

         Although the examples which follow discuss UPSs, many of the same principles apply to DC battery
         systems.


9.2      Main and Backup Supplies to UPSs

         Some classification society rules require that UPSs are supplied from the main power distribution in a
         manner that supports the split in the overall redundancy concept. In the past, before this rule was
         implemented, it was quite common to find that all UPS were supplied from the emergency
         switchboard as shown in Figure 25. This arrangement can still be found on recent new-build vessels
         and, although there are advantages to this arrangement, it actually creates an opportunity for a fault in
         one part of the vessel’s main power distribution system to affect what should be a completely
         independent section if one of the UPSs has a faulty battery.

                                                                                EG




             Port 440V                                         Emergency 440V                             Starboard 440V



                                      NC           NC




                                                                         Emergency 230V
              Port Thruster Auxiliaries                                                            Starboard Thruster Auxiliaries




                                                 UPS                                 UPS
                                                  A                                   B


                                                                                                   Hidden Failure
                                                                                                     of Battery


                                                  Port                             Starboard
                                            Thruster Control                    Thruster Control

                                           Failure of the emergency 230V transformer or
                                         switchboard will B create a on DP to
                                      Figure 25 – UPS A and limit time common point battery
                                           endurance.     A hidden failure of the battery in
                                    UPS system arrangement for a be lost if the port
         Figure 25 shows a typical powerB will cause all thrusters to diesel electric vessel in which the UPSs for
                                    power and the starboard or 440V transformer
         the port thruster control systems system blacks out thruster control systems are supplied from the
                                    Both UPSs emergency 230V will also drop (online) type. In this failure
         emergency switchboard. fails ( as the are of the double conversion out).
         scenario, which has happened several times in real life, UPS B has a hidden failure in the form of a
                                    Thrusters may be recovered, but valuable time
                                    will circuit several seconds after position.
         faulty battery which goes openbe lost and the vessel will losetransfer to battery supply. The initiating


44                                                                                                                      IMCA M 196
         fault leading to loss of position is a spurious trip of the circuit breaker on the secondary side of the
         port 440V service transformer such that the port thruster auxiliaries lose power leading to loss of
         50% of the thrusters. Unfortunately, the port LV switchboard also supplies the emergency
         switchboard which blacks out until the emergency generator connects. Because the batteries in UPS
         B are faulty, control power is lost to all the other thrusters which are then rejected from DP control
         and position is lost.

         In modern vessels, it is far more common to provide important UPSs with two supplies, one from an
         appropriate part of the main power system commensurate with the equipment that the UPS supplies.
         For example, in Figure 25, UPS A would have a normal supply from the port 440V switchboard and
         UPS B would have a normal supply from the starboard 440V switchboard. In this way, a faulty battery
         cannot compound a simple UPS failure leading to loss of position. Figure 26 shows the type of
         arrangement used to provide a backup supply to each UPS from the emergency switchboard. An auto
         changeover provides some protection against premature battery failure. A similar effect can be
         obtained by supplying the UPSs’ auto-bypass from the emergency switchboard rather than from the
         same switchboard as the rectifier input of the UPS. In all cases where redundant elements are linked
         by auto-changeovers, the effect of hidden failures and transfer of fault must be considered in the
         design. If it is decided that an auto-changeover is not required then it can still be useful to have a
         manual changeover to allow UPS batteries to be charged during drydock and at other times when
         main power is not available, for example, if blackout recovery takes longer that 30 minutes.

                                        MAIN                EMERGENCY
                                       POWER                  POWER
                                       SUPPLY                 SUPPLY



                                         )
                                                                  )



                                        NORMAL               BACK UP
                                        POWER                POWER
                                        SUPPLY               SUPPLY

                                                                       MANUAL OR AUTO
                                                                        CHANGEOVER


                                                    UPS
                                                    OR
                                                 DC POWER
                                                  SUPPLY




                          Figure 26 – Auto-changeover for UPS or DC power supply input


9.3      Static Switches

         Static (semiconductor) switches are used in standby and online UPSs to switch the load power
         between the inverter output and the main supply. Static switches are generally constructed from
         back-to-back SCRs (thyristors). Transfer times are quoted as being of the order of 4ms which is
         quarter of a cycle at 60Hz power frequency. The power interruption experienced with load transfer
         in a line interactive UPS is also of this order. Provided that detection of loss of power does not
         extend the transfer time to significantly more than 4ms, most IT loads using switched mode power
         supplies will not malfunction during the transfer. In fact, any unsatisfactory performance is not likely
         to be associated with the transfer time but rather the detection time, or lack of sophistication in
         detecting unacceptable changes in the input waveform. Therefore, it would be prudent to determine
         the overall transfer time for a range of conditions and confirm the effect. For a standby or line
         interactive UPS, poor switching performance causing malfunction in the load could significantly reduce
         the reliability of the vessel as these types of UPS are expected to switch as power quality deteriorates
         and improves (this switching may occur frequently in a marine application). Transfer time is less of an
         issue for an online UPS as transfer to bypass should only occur on an inverter or distribution fault. In
         the case of a distribution fault there will be a significant power system disturbance anyway. The
         redundancy concepts of DP vessels should accept that a UPS can fail and transfer to bypass is only an


IMCA M 196                                                                                                     45
      enhancement. However, frequent malfunctions associated with poor switching would be unacceptable
      even if they did not lead to a loss of position, bent pipe or broken drill string.

      In UPSs which transfer from inverter mode to bypass mode to clear faults in the UPS distribution, the
      bypass needs to be rated to supply the fault current. Information available from the public domain
      suggests that some manufacturers undersize the bypass for continuous operation but provide a
      mechanical bypass across the SCRs in the form of a contactor. It is understood that this may
      contribute to unreliability in this type of UPS.

      Most online UPSs will keep their inverter output in synchronism with the raw main supply so long as it
      stays within acceptable limits. If the raw power quality deteriorates, however, the two supplies will be
      allowed to diverge and transfer to bypass will be inhibited.


9.4   Changeovers at UPS Output or in the Distribution Scheme

      Dual AC supplies are often provided to DP essential consumers such as VMS field stations operator
      stations, thruster control systems and the like. Typically, dry contact relays or contactors are often
      used for this purpose. The intention of such schemes is often to improve the worst case failure by
      providing a second supply to an important consumer such as a thruster or generator control unit.
      Figure 27 shows how this changeover arrangement can compromise the redundancy concept. In the
      arrangement shown, there are two main UPSs supplying power to three bow thrusters. The centre
      bow thruster has a dual supply from both UPSs. These UPSs also supply the DP control systems.
      There are two concerns with this arrangement related to a fault on the supply to the centre bow
      thruster:
         The selectivity of the over current protection in the distribution board might not be good enough
          to ensure that the fuse in the feeder blows and not the incomer. In this case the auto-changeover
          will operate and blow the incomer fuse at both UPS distribution boards failing the power to both
          DP control systems.
         The correct fuse may blow but the auto-changeover operates and blows the fuses on both UPSs
          distributions. The voltage dip causes both DP control systems to re-boot.

      This type of arrangement should be avoided but if it already exists, or there is no other solution, then
      the effect of a voltage dip should be proven. The changeover should be designed in such a way that it
      will not change over if the fault is in the changeover itself or the equipment it supplies.




                                          UPS                           UPS
                                           A                             B


                                                                                                   UPS
                                                                                               DISTRIBUTION
                                                                                                  BOARD




                                                                AUTOCHANGEOVER




                DP CONTROL                                                            DP CONTROL
                                  THRUSTER              THRUSTER           THRUSTER
                  SYSTEM                                                                SYSTEM
                                    ECU                   ECU                ECU
                     A                                                                     B




                                                FAULT



                                     T1                    T3                    T2



                             Figure 27 – Dual UPS arrangement with auto-changeover

46                                                                                                    IMCA M 196
10 Operational Issues

10.1     Safety Considerations

         Personnel considerations: UPSs and DC battery systems present some additional hazards
         compared to other types of electronic equipment but these can be adequately controlled by normal
         workplace management. Due to the presence of batteries and capacitors, lethal voltages may exist
         within enclosure even after the unit has been isolated. Battery banks contain large amounts of stored
         energy which can be released very rapidly in the event of a short circuit fault leading to explosion/fire.

         Manufacturers’ guidelines for maintenance should be followed by competent and approved personnel
         working within a permit-to-work system.

         Explosive effects: All lead acid batteries can release hydrogen if abused, incorrect charging voltage
         being the most likely cause of out-gassing. Hydrogen forms an explosive mixture with the oxygen in
         air at the right concentrations and UPS rooms should have adequate ventilation. Class rules provide
         guidelines on the type of compartment in which various sizes of wet cell battery banks and VRLA
         battery banks may be located.

         Corrosive effects: Lead acid wet cells contain sulphuric acid in liquid form. This may leak out if the
         battery casing breaks or bursts due to swelling of the plates and can attack metal enclosures and injure
         personnel. The usual precautions and personal protective equipment for handling corrosive
         substances should be available. Statutory and company regulations may apply for the handling of such
         materials.

         Area/location considerations: Class rules contain requirements for the location of battery banks
         in relation to hazardous area classification and these should be followed. Typically, rules for mobile
         offshore drilling units may specify that compartments containing batteries should be considered as
         Zone 2 hazardous areas and the equipment within them suitable for operation in Zone 1. However,
         this is a specialised subject and the reader is directed to the rules of the appropriate classification
         society.

         Ventilation requirements: These are also set out in class rules but, typically, requirements apply
         to all types of rechargeable batteries with some distinctions made between those batteries having a
         liquid or dry electrolyte. The ventilation inlet should be in the lower part of the compartment and the
         outlet in the upper part so that pockets of gas cannot form. Ventilators should be so designed that
         they cannot be closed and the outlets should be located above the main deck. Some classification
         societies will permit variation of forced ventilation rates if multi stage charges are used so that a
         reduced ventilation rate is applied when the batteries are on float charge switching automatically to a
         higher ventilation rate when the charging current exceeds a defined level.


10.2     Environmental Considerations

         Transport and disposal considerations: All types of batteries commonly used aboard vessels are
         potentially toxic and should be disposed of responsibly. The transportation and disposal requirements
         of the country in which the vessel requires to transport or dispose of batteries should be followed.
         Vessel operators should be aware that batteries may be treated as hazardous or toxic waste and there
         may be restrictions on disposal and transportation. Battery testing companies may be able to provide
         a transport and disposal service as might some recycling companies.

         Nickel-cadmium batteries used in DC power supplies for switchboards may attract particular
         attention from regulatory bodies due to the toxicity of cadmium.




IMCA M 196                                                                                                       47
11 Suitability for Marine Applications

11.1   General

       The marine environment presents significant challenges for electronic equipment designers including:
          heat;
          vibration;
          humidity;
          saliferous atmospheres.

       As previously discussed, most UPS units installed on vessels are designed and built originally for
       commercial or factory use. However, all electronic equipment installed on vessels which forms part of
       the propulsion system must be approved by the relevant classification society who may well attend the
       FAT for the equipment to make sure it meets their requirements.

       Many DP vessels have unmanned machinery space notation in addition to their DP notation. Some
       classification societies link the requirements of their DP notation to the construction requirements of
       their unmanned machinery notation which set out construction requirements in more detail, for
       example:
          DNV – E0;
          ABS – ACCU;
          LRS – UMS.


11.2   Construction for Marine Environment

       The survey of vessel DC supplies and UPSs suggests that very few UPSs are purpose built for marine
       applications. Some manufacturers do have a marine range but survey results suggest that the majority
       of UPS installations on vessels are either standard commercial units or ruggedised version of
       commercial units built into larger steel enclosures. These ruggedised versions may include an external
       battery bank and distribution.

       As battery life is severely affected by operation at elevated temperatures, a location should be chosen
       where the temperature and humidity is controlled. By locating UPSs in air conditioned spaces, such as
       electrical equipment rooms or switchboard rooms, much of the problems regarding corrosion of mild
       steel components or the galvanic action associated with connections between dissimilar metals are
       avoided but it is still relatively common to find battery chargers located in alleyways and other spaces
       without proper climate control.

       Vibration may be more difficult to deal with as vibration levels can still be relatively high even in air
       conditioned spaces such as switchboard rooms. This is due to their close proximity to the main
       generators. Anti-vibration mounting may help as will securely mounting commercial components with
       a ruggedised case.


11.3   Design for Marine Applications – UPS

       From the information and issues discussed above, it is possible to put together a specification for a
       UPS for a marine application. Suggested arrangements for UPS and DC systems are shown in Figure
       28 and Figure 29.




48                                                                                                    IMCA M 196
                                         UPS UNIT AND BATTERY BOX

             BREAKER OPEN
               INDICATION
                                                   UPS
              AC SUPPLY                                                        BATTERY TEST FUNCTION
                                           (SEE VARIOUS TYPES)



                                                                         GENERAL FAULT
                                                                         SHUT DOWN EXTERNAL SYSTEM
                                                                         MAINS FAILURE
                                                                         EARTH FAULT
                                                    LOCAL CONTROL
                                                                         CHARGER FAULT CONDITION
                                                    AND INDICATION
                                                                         UPS INTERNAL BYPASS ON
                                                                         UPS FAULT CONDITION
                                                                         BATTERY IN DISCHARGE
                                                                         BATTERY VOLTAGE LOW
                                                                         METAL SEPARATION
                    ESD
                 INTERFACE                                               BREAKER OPEN
                IF REQUIRED                                              INDICATION

                                                                         BATTERY BOX WITH CORRECT
                                                     CELLS
                CB OPEN                                                  SPILL TRAY FOR CELL TYPE
               INDICATION                                                SUITABLE FOR EASY INSPECTION


                              SEE NOTE 1

                                                      BATTERY BANK
                                                   TEMPERATURE ALARM


                 AC BYPASS SUPPLY



                                               DISTRIBUTION PANEL


                                     A
                                                                     V

                  MANUAL
                BYPASS AND
                                 A
                 FILTER IF                                                                  NOTE 1:
                 REQUIRED                                                BREAKER OPEN       IF BATTERY BANK CELLS ARE WET TYPE,
                                                                         INDICATION         BATTERY BOX TO BE SEPARATE
                                                                                            NOTE 2:
                                                                                            IF DUAL SUPPLY BOTH SUPPIES TO BE
                                              MULTI OUTPUTS                                 ALARMED


                          Figure 28 – Design of UPS arrangement suitable for marine applications

         Typical marine UPS: A typical marine UPS should of course meet all the requirements for
         electrical compatibility discussed in Section 6. In addition, the UPS needs to comply with classification
         society rules as discussed in Section 8. Figure 28 shows a typical layout in which the UPS and its
         distribution are located in separate enclosures so that, in the event of a severe fault within the UPS,
         the distribution will not be affected and the manual bypass can still be used to supply the load.
         Although the battery compartment is shown within the same enclosure as the UPS itself, this is only
         possible if the batteries are not of the wet cell type. Although it is very common and convenient to
         include the battery bank within the UPS enclosure, consideration could be given to having a separate
         battery bank to improve access for routine inspection of the batteries. Many UPSs provide
         information by way of a single line LCD display on the UPS itself. This may be difficult to view when a
         commercial UPS is relocated within a ruggedised enclosure and it may be useful to add additional
         instruments to the UPS distribution.

         Interfaces should include:
              Mains failure alarm;
              Battery in discharge;
              In bypass mode;
              Inverter fault;
              Charger fault;
              General fault;
              Shutdown external systems (if required);

IMCA M 196                                                                                                                        49
          Circuit breaker indication;
          Remote battery isolation for ESD;
          Battery disconnected (cell and/or bank);
          Battery voltage low;
          UPS on alternative AC supply (if dual supply);
          Earth fault.


11.4   Design for Marine Applications – DC Supply

       Typical marine DC power supply: A typical marine DC power supply should meet all the
       requirements for electrical compatibility discussed in Section 6. In addition to this, the DC power
       supply needs to comply with classification society rules as discussed in Section 8. Figure 29 shows a
       typical layout in which the rectifier control unit, the distribution and the battery bank are located in
       separate enclosures.

       Interfaces Include:
          Mains failure;
          Battery in discharge;
          Charger fault;
          Boost charger on /trickle off – (may be required for ventilation control);
          ESD interface;
          Output voltage too high;
          Charge indication;
          Earth fault.




50                                                                                                   IMCA M 196
                                              BATTERY CHARGER PANEL




                   AC INPUT




                                                                                  CHARGER FAULT CONDITION

             BREAKER OPEN                                          LOCAL          DC OUTPUT VOLTAGE HIGH
               INDICATION                                         CONTROL         MAINS FAILURE
                                                                    AND           BATTERY IN DISCHARGE
                                                                 INDICATION

                                                                                  BOOST CHARGE ON




                                            DUAL FLOW
                                                             DISTRIBUTION PANEL
                                            AMMETERS




                                                                                  BREAKER OPEN
                                       A                 A              V
                                                                                  INDICATION




                                                 MULTI OUTPUTS

                              DC SUPPLY

                                 BREAKER OPEN INDICATION




                                                        CELLS
                                                                                  BATTERY BOX WITH
                                                                                  CORRECT SPILL TRAY FOR
                                                                                  CELL TYPE
                                      SHUNT
                                       TRIP


                                  ESD             BATTERY BANK
                               INTERFACE       TEMPERATURE ALARM
                              IF REQUIRED


                 Figure 29 – Design of DC power supply arrangement suitable for marine applications




IMCA M 196                                                                                                  51
12 References
The following sources of information were used in the preparation of this guidance document:
1    Samstad J, Hoff M – Technical Comparison Online Vs Line-Interactive UPS designs – SPC White Paper #79
2    Anon – Understanding Power Factor, Crest Factor an Surge Factor – APC White Paper #17
3    IEC 62040 from which is derived BS EN 62040-3:2001 – Uninterruptible Power Systems (UPS)
4    NEMA Standards Publication PE 1-2003 – Uninterruptible Power Systems (UPS) – Specification and Performance
     Verification
5    IEEE Std 450-2002 IEEE – Recommended Practice for Maintenance, Testing and Replacement of Vented Lead-Acid
     Batteries for Stationary Applications
6    IEEE Std 1188-2005, IEEE – Recommended Practice for Maintenance Testing and Replacement of Valve-Regulated
     Lead Acid (VRA) Batteries for Stationary Applications
7    IEEE Std 1184-2006 – IEEE Guide for Batteries for Uninterruptible Power Supply Systems
8    DNV Rules for Ships – Part 4 Chapter 8 January 2008 – Electrical Installations
9    DNV Offshore Standard DNV-OS-D201, January 2008 – Electrical Installations
10 DNV Offshore Standard DNV-OS-A101, October 2005 – Safety Principles and Arrangements (latest at time
   of writing)
11 ABS Rules for Building and Classing Steel Vessels 2008
12 ABS Rules Effects of Harmonics 2006
13 Lloyd’s Register of Shipping – Rules and Regulations for the Classification of Ships – 2006
14 Germanischer Lloyd – Rules & Guidelines 2008, Rules for Classification and Construction’, I – Ship Technology,
   Part 1 – Seagoing Ships, Chapter 3 – Electrical Installations
15 Public domain (Internet)




52                                                                                                     IMCA M 196
                                                                                                         Appendix 1


UPS Qualification Checklist

The following list can be used as an aid to the preparation of a specification for a UPS. Most manufacturers will
provide a detailed specification for comparison with specific requirements. It is inevitable that some aspects of
a specification will have to be negotiated with potential vendors as it is unlikely that manufacturers will have an
off-the-shelf product to fulfil every requirement.

Attention is drawn to Annex D of IEC Standard 62040-3 – Purchaser Specification Guidelines.
                Issue                                                   Notes
1    Type approval           Classification society
2    Construction            1    Standards NEMA/IEC/TUV or equivalent
                             2    Ingress protection
                             3    Hazardous zone rating
                             4    Anti condensation heaters
                             5    Surface preparation
                             6    Cable connections – glanding – terminations bottom/top/side entry
                             7    Nameplates
                             8    Service lighting
                             9    Audible noise
3    Ventilation             Size of battery bank many influence location and ventilation requirements
4    Metering                Voltmeters and dual direction ammeters for battery monitoring
5    Interface and alarms    1    UPS on batteries
                             2    UPS in bypass mode
                             3    Battery disconnected – (for each cell or for each bank)
                             4    Battery voltage low
                             5    Shut down external system
                             6    Earth fault
                             7    Charger fault
                             8    General fault
                             9    Battery over-temperature
                             10   Alarms for AC input(s) failed
                             11   Alarm for connection to alternative AC input (if dual supply)
                             12   Serial link to VMS
                             13   Battery test function required
                             14   Can interface be made application specific?
6    Type of UPS             Online (double conversion) preferred for critical applications
                             Line interactive
7    Input power             1    Input voltage
     specification           2    Input arrangement - number of phase/wires (3 wire, 4 wire, 5 wire)
                             3    Voltage variation
                             4    Rated frequency
                             5    Frequency range
                             6    Input power factor
                             7    Surge capability
                             8    Input current limit
                             9    Input current THD – (Can be 30% THD for MODU)
                             10   Surge withstand
                             11   Input phase rotation
                             12   Electronic noise isolation




IMCA M 196                                                                                                       53
              Issue                                                     Notes
8    Output power           13   Rated voltage
     specification          14   Output arrangement - number of phase/wires (3 wire, 4 wire, 5 wire)
                            15   Output capacity
                            16   Rated load power factor
                            17   Voltage regulation
                            18   Voltage adjustment range
                            19   Phase displacement
                            20   Phase rotation
                            21   Rated frequency
                            22   Frequency regulation
                            23   Frequency sync range (for auto bypass, etc.)
                            24   Frequency slew rate
                            25   Voltage transient on step change
                            26   Transient voltage recovery
                            27   Overload capacity on inverter
                            28   Overload capacity on bypass
                            29   Crest factor
                            30   Inrush current protection
                            31   Output over-current
9    Grounding              Protective earth
     arrangements           Equipotential bonding
                            Termination of steel wire armour or braid
10   Environmental          Operating temperature – (Critical for batteries)
     conditions             Storage temperature
                            Humidity
                            Vibration
                            Saliferous atmospheres
11   Battery type           Lead acid wet cell – VRLA – Nickel-cadmium
12   Battery endurance      30 minutes minimum for DP plus margin for load growth and aging, etc. See manufacturer’s
                            run-time charts
13   Battery service life   3 to 5 year or 5 to 7 year typical.
                            Operating temperature – Note manufacturers do not always refer service life to the same
                            operating temperature so it may be necessary to correct the service life figure for the actual
                            operating temperature or for comparison of batteries.
14   Battery charger        Battery management features
                            Ripple factor – effect on battery life
                            Hot Swap facility for batteries
15   Bypass requirements    1    Manual bypass
                            2    Auto bypass
                            3    Bypass from different source to UPS input
                            4    Bypass from same source as UPS input
16   ESD requirements       Disconnection of batteries – Ability of UPS to restart from batteries
17   Number of AC input     Type of changeover
     supplies
18   Protection and         Fuses – Semiconductor fuses for inverter protection
     coordination           Circuit breakers – MCBs for distribution
                            Ability to isolate faults in distribution selectively
19   FAT and CAT            Programs to be agreed and submitted for review
20   Warranty & service     Availability of service technicians world wide
     support
21   Documentation          Compliance/approval certificates
                            Service manuals
                            Electronic and general arrangement drawings




54                                                                                                             IMCA M 196
                                                                                                                                                                                    Appendix 2
IMCA M 196




             Data on UPS, DC Power Supplies and Batteries

             Survey of Owners and Operators of UPS Equipment
                              UPS
                              Manufacturer                                 Input/Output        Power/Duration
             Type of vessel   Code           Battery Type                  Voltage of System   at Full Load     System Usage   Owner’s Remarks
                              K              VRLA                          176-276V/208-                        UPS for        Pros:
                                             (5 Year)                      240V                                 integrated     Relatively short and to the point manual
                                                                                                                automation     Battery may be replaced without shutting down a system (feature
                                                                                                                system         called ‘hot swap’)
                                                                                                                               Easily configurable for various demands
                                                                                                                               Battery test feature. Thanks to this the battery can be proven
                                                                                                                               operative without shutting down the system. It is very useful
                                                                                                                               Ready to use dual mains input for getting connected to separate
                                                                                                                               power supplies which is a step forward in terms of the overall
                                                                                                                               system reliability
                                                                                                                               Cons:
                                                                                                                               Lack of NC/NO alarm output instead of existing RS232. In case
                                                                                                                               of remote location easier solution would be to hook it up to the
                                                                                                                               monitoring system DI instead of setting up a network so as such
             Pipelayer                                                                                                         option would be appreciated
                                                                                                                               Reliable, maintenance free, no problems experienced so far
                              C              Maintenance-free sealed       220V/220V           400W/650VA       Thruster VFD   Pros:
                                             lead-acid battery with                            5 mins           controls       All details necessary for getting them installed available as printed
                                             suspended electrolyte: leak                                                       on the rear of the body
                                             proof                                                                             Standard connections
                                                                                                                               Cons:
                                                                                                                               Self-contained with battery which broke in one of them within less
                                                                                                                               than two years’ time
                                                                                                                               Plastic enclosure might be not robust enough for marine
                                                                                                                               environment
                                                                                                                               No experience of any spectacular breakdowns to batteries nor to
                                                                                                                               UPSs other than caused by lack of maintenance resulting in rotten
                                                                                                                               poles, dry cells or incorrect application
55
                                   UPS
                                   Manufacturer                              Input/Output        Power/Duration
56




             Type of vessel        Code           Battery Type               Voltage of System   at Full Load     System Usage     Owner’s Remarks


                                                                                                                                   Above-mentioned UPS units perform as expected giving no troubles
                                                                                                                                   at all
                                   A              8pcs 12V DC, 7Ah           Input/output        3kVA 115V        UPS for drives
             Pipelayer                            (internal batteries)       voltage 115-120V                     2 units
                                   A              Batteries 10pcs 12V DC     Voltage in/out      3000VA, 120V                      None
                                                  28AH Panasonic (external   120V                Watts 2100
                                                  in cabinet)                                    Output current
                                                                                                 25A
                                   A              8pcs 12V DC, 7Ah           Input/output        3kVA 115V        Integrated       Six units of this type in service for seven years with only one failure
                                                  (internal batteries)       voltage 115-120V                     automation
                                                                                                                  system
             Construction vessel
                                   A              8pcs 12V DC, 7Ah           Input/output        3kVA 115V        Integrated
                                                  (internal batteries)       voltage 115-120V                     automation
                                                                                                                  system
                                   A              N/A                        N/A                 N/A              N/Av             No failures since installed
                                   A                                                             120V/230 input   N/A
             Pipelayer                                                                           120V/230V
                                                                                                 output
                                   C              N/A                        N/A                 120V/1750W       N/A
                                   A              8pcs 12V DC, 7Ah           Input/output        3kVA 115V        N/A              UPS failures primarily attributed to battery bank failure due to age.
                                                  (internal batteries)       voltage 115-120V                                      One unit failed in such a way trip off-line when a UHF portable
                                                                                                                                   handheld radio was keyed immediately adjacent to it
                                   D                                         220V                                 DP               None
             Shuttle Tanker
                                   L              3 7Ah sealed lead acid     220V/230V           1000VA           Cargo system     None
                                                  batteries 36V DC
                                   L              6 7Ah sealed lead acid     220V/230V           2000VA           Cargo system     None
                                                  batteries 72V DC
                                   M              N/A                        N/A                 N/A              Thruster VSD     These are not a marine product but even so they have been very
                                                                                                                  control and      reliable. They advertise the design as having been specifically
                                                                                                                  other            made to work with stand alone generators and they do deal with
             DP Drilling vessel                                                                                   applications     frequency variation more gracefully than many UPS products from
IMCA M 196




                                                                                                                                   others. These are all on line designs
                                   N              N/A                        N/A                 N/A              N/A              These contain a ferro-resonant transformer and tend to be pretty
                                   UPS
                                   Manufacturer                  Input/Output        Power/Duration
IMCA M 196




             Type of vessel        Code           Battery Type   Voltage of System   at Full Load     System Usage   Owner’s Remarks
                                                                                                                     reliable.
             General comments      N/A            N/A            N/A                 N/A              N/A            We have had problems with ferro-resonant type UPS units where
             drilling contractor                                                                                     there were loads that had inrush, the ferro is self-protecting for
                                                                                                                     over-current at its output so if load inrush applies a current
                                                                                                                     demand over the rating the output voltage collapses
                                                                                                                     Many UPS units do not work well with harmonics on incoming or
                                                                                                                     with power line frequency that varies. Most UPS units are used on
                                                                                                                     land with utility power that never varies in frequency so their basic
                                                                                                                     design often does not account for frequency deviations with
                                                                                                                     sufficient sophistication
                                                                                                                     Most of our UPS units are the on line type, where the output
                                                                                                                     inverter is providing power continuously from the DC link. We have
                                                                                                                     not had very good results with the line interactive type where the
                                                                                                                     inverter only switches on and provides power in certain defined
                                                                                                                     conditions and the rest of the time the power is directly from the
                                                                                                                     line
                                                                                                                     We have had problems with reluctance of UPS manufacturers to
                                                                                                                     configure alarms to our requirements. This has been ridiculous in
                                                                                                                     some cases, for example alarms on line frequency. Once we even
                                                                                                                     replaced a German UPS because of this
                                                                                                                     Most technical problems we have had with UPS units have been
                                                                                                                     with the batteries. We use UPS units with critical loads; the only
                                                                                                                     way to be sure the UPS batteries will support the UPS is a load
                                                                                                                     test but that generally means if the batteries do not perform we
                                                                                                                     would be at risk of dropping the load. So the maintenance guys
                                                                                                                     are reluctant to load test the UPS batteries using the actual load
                                                                                                                     on the UPS. So I think the guide should address maintenance
                                                                                                                     strategy for UPS units
                                                                                                                     We do have a concern with powering many loads from one UPS
                                                                                                                     and whether a short circuit fault at one of the loads will be cleared
                                                                                                                     without disturbance of the other loads
57
             Survey of Owners and Operators of DC Equipment
58




                              DC System                          Input/Output
                              Manufacturer                       Voltage of     Current/Duration   System
             Type of vessel   Code           Battery Type        System         at Full Load       Usage           Owner’s Remarks
                              O              Separate, 9 x       230V AC/108    22.2A/N/A          Switchboard     Few if any problems with these units. However in one unit the control PCB failed in
                                             sealed,                                               controls        the past but no further details available
                                             maintenance free,
                                             lead acid
                                             automotive-like
             Pipelayer                       batteries 12V
                              P              3pcs, 24V banks     230V AC/24V    100A               Thrusters       No problems so far neither with these units nor with batteries managed by them.
                                             of 4 x              DC                                controls and    Robust stand alone construction and reliable performance
                                             nonspillable 6V                                       other uses
                                             190Ah
                              J              N/A                 230V/110V DC   N/A                Not specified   This is unfortunately obsolete after only one year in service with the rectifying
                                                                                                                   modules irreplaceable. This system comprises several rectifying modules thus
             Shuttle tanker
                                                                                                                   allowing the loss of one and the system still functions. Note to date we have lost
                                                                                                                   three modules after three years of service
                              G              NiCAD               220V AC/110V   15A                SWBD            None
             Pipelayer
                                                                 DC                                controls
                              J              N/A                 24V DC                            Thruster        None
                                                                                                   controls and
                                                                                                   automation
                                                                                                   system
                              J              N/A                 24V DC                            Bow loading
                                                                                                   system
             Shuttle tanker   J              N/A                 24V DC                            Bow loading
                                                                                                   system

                              J              N/A                 24V DC         30A                Bridge
                              J              N/A                 110V DC                           HV
                                                                                                   Switchboard
                                                                                                   controls
IMCA M 196
             NDC Desktop Survey of UPS Types
IMCA M 196




                            Number of                                  Type of                                                                ESD
             Vessel Type    Systems     System Usage     Manufacture   System          Battery Type     Power/voltage     Bypass facility     Facility   Remarks
                            5 AC UPS    DP and IAS       A             Online/double   32X 7Ah VRLA     210kVA/9kW/230V   Manual bypass       N/A        Manufacturers’ original
                                                                       conversion      455V                               and auto                       enclosure mounted on frame
                                                                                                                          transfer to                    with vibration mounts
                                                                                                                          bypass on
             Pipe layer                                                                                                   overload
             DP3
                            7 DC PS     IAS and SWBD     G             N/A             N/A              24V DC            N/A                 N/A        Manufacturer’s original
                                        control                                                                                                          enclosure
                            2 DC PS     HV SWBD          G             N/A             N/A              110V DC           N/A                 N/A        Manufacturer’s original
                                                                                                                                                         enclosure
             Diving         N/A         N/A              N/A           N/A             N/A              N/A               N/A                 N/A        No information available or
             Vessel                                                                                                                                      provided
                            4 AC UPS    DP and IAS       F             Online & Line   N/A              5-6kVA 230V       Manual bypass       No         Mounted in ruggedised
                                                                       interactive                                        and auto                       enclosure provided by the
                                                                                                                          transfer to                    DP Control system
                                                                                                                          bypass on                      manufacturer
                                                                                                                          overload
             DP3 Drilling   2 DC PS     HV SWBD          G             N/A             NiCAD SBL 30     110V DC           N/A                 No         Manufacturer’s original
             semi-sub                                                                                                                                    enclosure
                            2 DC PS     Engine control   G             N/A             NiCAD SBL 30     24V DC            N/A                 No         Manufacturer’s original
                                                                                                                                                         enclosure
                            2 AC UPS    Fire and gas     D             Online          VRLA             5 kVA             N/A                 No         Manufacturer’s original
                                                                                                                                                         enclosure
                            3 AC UPS    DP and IAS       B             Online          29 by 26Ah/12V   15 kVA/208V       Manual bypass       No         Manufacturer’s original
                                                                                                        input/120V/240V   and auto                       enclosure with addition of
                                                                                                        output            transfer to                    auto-changeover for dual
             DP2 Drilling                                                                                                 bypass (static                 input supply – status LEDs
             semi-sub                                                                                                     switch) in                     provided
                                                                                                                          detection of
                                                                                                                          inverter fault or
                                                                                                                          overload
59
                            Number of                                    Type of                                                                   ESD
             Vessel Type    Systems     System Usage       Manufacture   System        Battery Type       Power/voltage        Bypass facility     Facility   Remarks
60




                            2 AC UPS    IAS and thruster   B             Online        N/A                5 kVA/208V           Manual bypass       No         Manufacturer’s original
                                        control                                                           input/120V/240V      and auto                       enclosure with addition of
                                                                                                          output               transfer to                    auto-changeover for dual
                                                                                                                               bypass (static                 input supply – status LEDs
                                                                                                                               switch) in                     provided
                                                                                                                               detection of
                                                                                                                               inverter fault or
                                                                                                                               overload
                            2 AC UPS    IAS and thruster   B             Online        N/A                8 kVA/208V           Manual bypass       No         Manufacturer’s original
                                        control                                                           input/120V/240V      and auto                       enclosure with addition of
                                                                                                          output               transfer to                    auto-changeover for dual
                                                                                                                               bypass (static                 input supply – status LEDs
                                                                                                                               switch) in                     provided
                                                                                                                               detection of
                                                                                                                               inverter fault or
                                                                                                                               overload
                            4 AC UPS    IAS and thruster   B             Online        N/A                2 kVA/208V           Manual bypass       No         Mounted in Rittal cabinet
                                        control                                                           input/120V/240V      and auto                       with glass front – modular
                                                                                                          output               transfer to                    withdrawable battery banks
                                                                                                                               bypass (static
                                                                                                                               switch) in
             DP2 Drilling                                                                                                      detection of
             semi-sub                                                                                                          inverter fault or
                                                                                                                               overload
                            2 DC PS     SWBD control       H             N/A           N/A                110V DC              Manual bypass       No         Purpose built cabinets – with
                                                                                                                               and auto                       remote battery bank
                                                                                                                               transfer to
                                                                                                                               bypass (static
                                                                                                                               switch) in
                                                                                                                               detection of
                                                                                                                               inverter fault or
                                                                                                                               overload
                            8 AC UPS    VSD control        C             Line          Maintenance free   1500VA/120V                              No         Commercial UPS in rack
                                                                         interactive   lead acid with     input, 120V output                                  mount form
                                                                                       suspended
                                                                                       electrolyte
IMCA M 196
                           Number of                                Type of                                                               ESD
             Vessel Type   Systems     System Usage   Manufacture   System    Battery Type        Power/voltage         Bypass facility   Facility     Remarks
IMCA M 196




                           3 DC PS     SWBD control   G             N/A       SBL30 nickel-                             N/A               Yes –        The battery charger feeds
                                                                              cadmium wet cell                                            MCB          the battery bank and then
                                                                              supply – 84 cells                                           Tripped      one supply to the
                                                                              at 9amp 20 years                                            by a 24V     distribution board. The
                                                                                                                                          DC shunt     system consists of three
             DP3                                                                                                                          trip         units, battery charger,
             Drillship                                                                                                                    external     battery bank and distribution
                                                                                                                                          supplied     system separately mounted.
                                                                                                                                                       The switchroom 110V DC
                                                                                                                                                       supply systems are
                                                                                                                                                       interlinked but operate
                                                                                                                                                       independently
                           11 AC UPS   DP and IAS     E             Online    2 x 12V x 4         Input 110V AC         None              Yes –        The system consists of one
                                                                                                  output dual voltage                     MCB          panel. The system is a
                                                                                                  115V AC and 24V                         tripped by   modular design which has
                                                                                                  DC                                      a 24V DC     AC and DC distribution
                                                                                                                                          shunt trip   boards at the top, below is
             DP3                                                                                                                          external     rack mounted inverter
             Drillship                                                                                                                    supplied     modules the below that rack
                                                                                                                                                       mounted rectifier modules
                                                                                                                                                       the two battery shelves are
                                                                                                                                                       at the bottom
                           1 DC UPS    Marine and     I             N/A       N/A                 460V input/24V        N/A               N/A          Purpose built enclosure
                                       emergency                                                  DC output, 60A
61
                           Number of                                  Type of                                                              ESD
             Vessel Type   Systems     System Usage     Manufacture   System    Battery Type         Power/voltage   Bypass facility       Facility   Remarks
62




                           3 AC UPS    Nav, comms and   D             Online    Sealed lead acid 8   120V            Yes                   Yes –      UPS panel with a distribution
                                       backup DP                                x 12V 7.2Ah 4-5                      Internal              MCB        system and bypass facilities.
                                                                                years                                automatic             Tripped    Input 120V AC. This type of
                                                                                                                     bypassing all         by a 24V   panel is also supplied with
                                                                                                                     UPS internals         DC shunt   two systems (dual) within
                                                                                                                     inclusive of filter   trip       one panel with the two UPSs
                                                                                                                     Manual system         external   on the top shelf and the
                                                                                                                     external to UPS       supplied   bypass and distribution
                                                                                                                     by selector                      systems below. The system
                                                                                                                     switch within                    consists of one panel
                                                                                                                     cubicle                          (batteries within UPS unit)
                                                                                                                                                      which is a self-contained unit
                                                                                                                                                      mounted in the top of the
                                                                                                                                                      cabinet with the manual
                                                                                                                                                      bypass switch and output
                                                                                                                                                      distribution mounted below
IMCA M 196
             VRLA Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation
IMCA M 196




                                                        Information                                          Valve
             Manufacturer   Information   Vessel        from                                                 Regulated      Battery   Battery             Battery Life
             of UPS         from Vessel   Technical     Desktop         System     System     Manufacturer   Lead Acid      Type      Cell      Battery   Expectancy
             System         Survey        Information   Investigation   Voltage    Usage      of Battery     Type           Number    Voltage   Ah        (Years)        Remarks
             J              No            Yes           No              120V ac    UPS        Not known      Information    Not       12V       7.2Ah     4 to 5         8 cells listed as battery
                                                                                                             given as       known                         Years          bank
                                                                                                             sealed lead
                                                                                                             acid only
             K              Yes           No            No              208-       UPS        Not known      Information    Not       Not       Not       5 years        System type
                                                                        240V ac                              given as       known     known     known                    information was online
                                                                                                             VRLA only
             C              Yes           No            No              220V ac    UPS        Not known      Information    Not       Not       Not       Not known      System type
                                                                                   thruster                  given as       known     known     known                    information was online-
                                                                                   VFD                       maintenance-                                                backup
                                                                                   controls                  free sealed
                                                                                                             lead-acid
                                                                                                             battery with
                                                                                                             suspended
                                                                                                             electrolyte:
                                                                                                             leak proof
                                                                                                             only
             A              Yes           No            No              !20V ac    UPS for    Not known      Information    Not       12V       7Ah       Not known      8 cells listed as battery
                                                                                   drives 2                  given as       known                                        bank
                                                                                   units                     sealed lead                                                 System information was
                                                                                                             acid only                                                   9120 series 3kVA
             A              Yes           No            No              120V ac    UPS        Panasonic      Information    Not       12V       28Ah      Not known      10 cells listed as battery
                                                                                                             given as       known                                        bank.
                                                                                                             sealed lead                                                 System information
                                                                                                             acid only                                                   3000VA, 120V Watts
                                                                                                                                                                         2100
                                                                                                                                                                         Output current 25A
             L              Yes           No            No              220/230V   UPS for    Not known      Information    Not       36V       7Ah       Not known      3 cells listed as battery
                                                                        ac         cargo                     given as       known                                        bank.
                                                                                   system                    sealed lead                                                 System information
                                                                                                             acid only                                                   1000VA
63
                                                        Information                                             Valve
             Manufacturer   Information   Vessel        from                                                    Regulated        Battery   Battery              Battery Life
64




             of UPS         from Vessel   Technical     Desktop         System     System        Manufacturer   Lead Acid        Type      Cell      Battery    Expectancy
             System         Survey        Information   Investigation   Voltage    Usage         of Battery     Type             Number    Voltage   Ah         (Years)        Remarks
             O              Yes           No            No              108V dc    Switchboard   Not known      Information      Not       12V       Not        Not known      9 cells listed as battery
                                                                                   controls                     given as         known               known                     bank.
                                                                                                                sealed,                                                        System information
                                                                                                                maintenance                                                    DCPS 108-22 at 22.2A.
                                                                                                                free, lead
                                                                                                                acid
                                                                                                                automotive-
                                                                                                                like batteries
                                                                                                                only
             S              Yes           No            No              24V dc     Not known     Not known      Information      Not       6V        190Ah      Not known      4 cells x 6V = 24V 3pcs
                                                                                                                given as non-    known                                         make up battery bank.
                                                                                                                spill only                                                     System information
                                                                                                                                                                               M6V 190F
             Q              Yes           No            No              24V dc     Ballast and   SAE            Information      Not       12V       25Ah       Not known      2 cells listed as battery
                                                                                   bilge                        given as         known                                         bank.
                                                                                   control                      cycle gel cell
             N/A            No            No            Yes             As         UPS           Yuasa          VRLA AGM         NP        12V       Range      5 years        Years rating at 20° C
                                                                        required                                                 series              of sizes
             N/A            No            No            Yes             As         UPS           Yuasa          VRLA AGM         NPL       12V       Range      7 to 10        Years rating at 20° C
                                                                        required                                                 series              of sizes   years
             N/A            No            No            Yes             As         UPS           Panasonic      VRLA AGM         RW        4/6/12V   Range      5 years        Years rating at 20°C on
                                                                        required                                                 series              of sizes   3 to 5 years   trickle charge
                                                                                                                                                                               Years rating at 25°C on
                                                                                                                                                                               trickle charge
             N/A            No            No            Yes             As         UPS           Panasonic      VRLA AGM         PW        4/6/12V   Range      10 years       Years rating at 20°C on
                                                                        required                                                 series              of sizes   6 years        trickle charge
                                                                                                                                                                               Years rating at 25°C on
                                                                                                                                                                               trickle charge
             N/A            No            No            Yes             As         UPS           Enersys        VRLA AGM         Odyssey   12V       Range      Design life    Years rating at 20°C
                                                                        required                                                 series              of sizes   = 12 years
                                                                                                                                                                Service life
                                                                                                                                                                = 6 to 8
                                                                                                                                                                years
IMCA M 196
                                                        Information                                        Valve
             Manufacturer   Information   Vessel        from                                               Regulated   Battery    Battery              Battery Life
IMCA M 196




             of UPS         from Vessel   Technical     Desktop         System     System   Manufacturer   Lead Acid   Type       Cell      Battery    Expectancy
             System         Survey        Information   Investigation   Voltage    Usage    of Battery     Type        Number     Voltage   Ah         (Years)        Remarks
             N/A            No            No            Yes             As         UPS      Exide          VRLA AGM    Absolyte   4V        Range      20 years       Years rating at 25°C on
                                                                        required                                       XL                   of sizes                  float charge.
                                                                                                                       series
             N/A            No            No            Yes             As         UPS      Exide          VRLA AGM    Marathon   6/12V     Range      12 years       Years rating at 20°C
                                                                        required                                       L series             of sizes                  (80° remaining charge)
             N/A            No            No            Yes             As         UPS      Exide          VRLA AGM    Sprinter   6/12V     Range      10 years       Years rating at 20°C
                                                                        required                                       series               of sizes                  (80° remaining charge)
             N/A            No            No            Yes             As         UPS      Exide          VRLA AGM    Power      6/12V     Range      7 years        Years rating at 20°C
                                                                        required                                       Fit S500             of sizes                  (80° remaining charge)
                                                                                                                       series
             N/A            No            No            Yes             As         UPS      SBS            VRLA AGM    UPS        12V       Range      10 years       Years rating at 20°C
                                                                        required                                       HR                   of sizes
                                                                                                                       series
             N/A            No            No            Yes             As         UPS      SBS            VRLA AGM    UPS        6/12V     Range      7 years        Years rating at 20°C
                                                                        required                                       S series             of sizes
             N/A            No            No            Yes             As         UPS      SBS            VRLA Gel    G series   6/12V     Range      10 years       Design years rating at
                                                                        required                                                            of sizes                  20°C on float charge.
                                                                                                                                                       8 to 10        Service years rating at
                                                                                                                                                       years          20°C on float charge.
65
             Wet Cells – Results of Vessel Survey, Vessel Technical Information and Desktop Investigation
66




                                                        Information                                              Lead                                       Battery
             Manufacturer   Information   Vessel        from                                                     Acid or     Battery   Battery              Life
             of DC          from Vessel   Technical     Desktop         System     System         Manufacturer   Nickel      Type      Cell       Battery   Expectancy
             System         Survey        Information   Investigation   Voltage    Usage          of Battery     Cadmium     Number    Voltage    Ah        (Years)      Remarks
             G              No            Yes           No              110V       DC supply      Saft           Nickel      SBL 30    Not        Not       20 Years     84 cell battery bank. This is a
                                                                        DC         system for                    cadmium               known      known                  common cell type and
                                                                                   HV                                                                                    configuration found on DP
                                                                                   Switchboard                                                                           vessels
                                                                                   metering,
                                                                                   protection
                                                                                   and control
                                                                                   also AVR
                                                                                   control
             E              No            Yes           No              Dual       24V DC for     SBS60          Lead acid   3 banks   12V        Not       Not known    6 cell battery bank
                                                                        output     engine                                    of 2 x               known                  Dual systems are utilised on
                                                                        of 115V    control,                                  12V                                         DP vessels but cannot be
                                                                        AC and     governor                                  cells                                       regarded as common
                                                                        24V DC     control, DG
                                                                                   speed
                                                                                   control and
                                                                                   also process
                                                                                   stations.
                                                                                   115vAC for
                                                                                   O/S
             R              Yes           No            No              24V DC     24V DC         Varta          Lead acid   Vb12149   12V        Not       Not known    4 separate 24V banks of 2 x
                                                                                   ballast and                                                    known                  12V = 8 cell battery bank
                                                                                   bilge
                                                                                   control
             N/A            No            No            Yes             24V and    DC supply      Saft           Nickel      SBL       1.2V       Wide      20 years     This battery type has valve
                                                                        110V       system                        cadmium     range     nominal    range.                 regulated pocket plate
                                                                        DC –                                                           per cell                          technology and is listed as
                                                                        other                                                                                            low maintenance also this
                                                                        voltages                                                                                         battery is listed as usage in
                                                                        as                                                                                               UPS systems
                                                                        required
IMCA M 196
                                                        Information                                           Lead                                       Battery
             Manufacturer   Information   Vessel        from                                                  Acid or     Battery   Battery              Life
IMCA M 196




             of DC          from Vessel   Technical     Desktop         System     System      Manufacturer   Nickel      Type      Cell       Battery   Expectancy
             System         Survey        Information   Investigation   Voltage    Usage       of Battery     Cadmium     Number    Voltage    Ah        (Years)       Remarks
             N/A            No            No            Yes             24V and    DC supply   Saft           Nickel      SML       1.2V       Wide      20 Years      This battery type has valve
                                                                        110V       system                     cadmium     range     nominal    range                   regulated pocket plate
                                                                        DC –                                                        per cell                           technology and is listed as
                                                                        other                                                                                          low maintenance also this
                                                                        voltages                                                                                       battery is listed as usage in
                                                                        as                                                                                             UPS systems
                                                                        required
             N/A            No            No            Yes             24V and    DC supply   SBS            Lead acid   OPS       2V per     Wide      20-25 years   This type of battery has been
                                                                        110V       system                                 range     cell       range                   listed as DC systems as the
                                                                        DC –                                                                                           study research has highlighted
                                                                        other                                                                                          only one wet cell usage in a
                                                                        voltages                                                                                       UPS system. This was a dual
                                                                        as                                                                                             system with AC and DC
                                                                        required                                                                                       outputs
             N/A            No            No            Yes             24V and    DC supply   SBS            Lead acid   STT       2V per     Wide      20-25 years   This type of battery has been
                                                                        110V       system                                 range     cell       range                   listed as DC systems as the
                                                                        DC –                                                                                           study research has highlighted
                                                                        other                                                                                          only one wet cell usage in a
                                                                        voltages                                                                                       UPS system. This was a dual
                                                                        as                                                                                             system with AC and DC
                                                                        required                                                                                       outputs
67

								
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