RFQ No. 267/2002


           SECTION 3

                                                                              EAC SPEC. 14-013

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                                 POWER TRANSFORMERS

1     Scope

1.1     General

This specification covers the construction and system requirements for the design and
testing of one auto-transformer and associated equipment.

The auto-transformer shall comprise in addition to the main tank and associated equipment
a three phase automatic tap changer with associated panel.

Test requirements and test methods are included which are intended to demonstrate the
capability of the auto-transformer and its compliance to the declared values in the Schedules
of Particulars, which are attached to this document.

The auto-transformer and the associated equipment shall be delivered at Cyprus Port within
five (5) months from the award of the Contract. It should be noted that no request for
extension would be granted due to the urgency of the project.

1.2     Approved Types

1.2.1    Tap changers and associated relays

The tap changers and associated regulating relays shall be of the most recent type suitable
for the schemes covered by this Specification.

1.2.2    Auto-transformers

132/66 autotransformer 40/63MVA ONAN/ONAF complete with three phase on load tap
changer and associated control panel.

2     References

2.1     Normative references

This specification incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate place in the text and
the publications are listed in paragraph 2.3 below. For a dated reference, only the cited
edition applies: any subsequent amendments to or revisions of the publication apply to this
specification only when incorporated in the reference by amendment or revision. For
undated references, any amendments to, or the latest edition of, the cited publication

2.2     Informative references

This specification refers to other publications that provide information or guidance. Editions
of these publications current at the time of issue of the standard are listed in the paragraph
below, but reference should be made to the latest editions.
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2.3   List of References

Normative references

BSI standards publications

BS 88         Cartridge fuses for Voltages up to and including 1000 V a.c. and 1500
              V d.c.
BS 89         Direct Acting Indicating Electrical Measuring Instruments
BS 142        Electrical Protective relays
BS 148        Insulating oil for transformers and switchgear
BS 171        Power Transformers
BS 308        Engineering drawing practice
BS 381C       Colours for Identification Coding & Special Purposes
BS 443        Specifications for testing zinc coatings on steel wire
BS 646        Cartridge Fuse Links (rated up to 5 amperes) for AC & DC Service
BS 729        Hot dip galvanized coatings
BS 822        Terminal markings for electrical machinery and apparatus
BS 1133       Packaging Code
BS 1224       Electroplated Coatings of nickel and chromium
BS 1376       Colours of light signals
BS 1598       Ceramic insulating materials
BS 1780       Bourdon tube pressure and vacuum gauges
BS 2011       Basic environmental testing procedures
BS 2562       Specification for cable boxes for transformers and reactors
BS 2569       Sprayed Metal coatings
BS 2600       Methods of radiographic examination of fusion welded butt joints in
BS 2757       Classification of insulating materials
BS 2765       Dimensions of temperature detecting elements and corresponding
BS 2910       Methods for radiographic examination of fusion welded circumferential
              butt-joints in steel pipes
BS 3600       Specification for dimensions and masses per unit length of welded and
              seamless steel pipes and tubes for pressure purposes.
BS 3643       ISO metric screw threads
BS 3692       ISO metric precision hexagon bolts, screws and nuts
BS 3941       Voltage transformers
BS 4099       Specification for colours of indicator lights push buttons, annunciators
              and digital readouts
BS 4190       ISO metric black hexagon bolts, screws and nuts
BS 4360       Specification for weldable structural steels
BS 4504       Flanges and bolting for pipes, valves and fittings
BS 4571       Specification for on load tap changers
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BS 4794     Specification for control switches
BS 4872     Approval testing of welders
BS 4944     Reactors, arc-suppression coils and earthing transformers for electric
            power systems
BS 4963     Tests on hollow insulators for use in high voltage electrical equipment.
BS 5000     Rotating electrical machines
BS 5135     Metal arc welding of Carbon and carbon manganese steels.
BS EN       Low voltage switchgear and control gear.
BS 5490     Specification for degrees of protection provided by enclosures
BS 5493     Code of practice for protective coatings of iron and steel structures
            against corrosion
BS 6121     Mechanical cable glands for elastomer and plastics insulated cables.
BS 6231     PVC Insulated cables for switchgear & control gear wiring

IEC Standards Publications

IEC 76      Power Transformers
IEC 137     Insulated bushings for alternating voltages above 1kV
IEC 296     Insulating Oil for transformers and switchgear
IEC 354     Loading Guide for Oil Immersed Transformers
IEC 470     High voltage AC contactors
IEC 551     Method of measurement of transformer and reactor sound levels
IEC 694     Common clauses for high voltage switchgear & control gear standards
IEC 688-1   Electrical measuring transducers
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3.1.1    Site Operating Conditions

The climate is sub-tropical and the following meteorological information is set out for
guidance only and no responsibility for it will be accepted nor will any claims based on this
information be accepted. Nevertheless the values given below shall be taken into account in
designing the works.

Altitude of sites above sea level:                                    below 1000m
Maximum ever recorded outdoor               C                        50
ambient shade or indoor temperature for
design purposes
Minimum Temperature                         C                        -5
Relative humidity                          %                         100
Thunderstorms per year                                               30
Number of strokes to earth                                           4
per sq.km per year
Earthquake loading for design              Refer to Clause 3.1.6
3.1.2    General Design Information

Phase Rotation and Colour-Phases shall be distinguished as Red (R), Yellow (Y) and Blue
(B) with phases reaching their maximum values in that order in an anticlockwise rotation.

Nominal system voltage               kV   132             66              11
between phases
Rated Voltage                        kV   145             72              12
Rated short-circuit and                   31.5 for        25 for          20 for
through fault capability Ka               1 sec           1 sec           3 sec.
Earthing of System                        Solid           Solid           Solid Earthing of
                                          Earthing        Earthing        the 11kV neutral or
                                                                          of zig-zag earthing

System        ratio : 20

System Frequency: 50 Hz

A.C. supply voltage for auxiliary equipment: 400/230 V

D.C. Supply voltage for auxiliary equipment: 110V d.c. 2-wire

Closing: 110V d.c.
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Tripping: 110V d.c.

Initiating power supply for indications and alarms: 110V d.c.

The equipment provided under this Contract is to be capable of operating reliably within the
following voltage ranges:

(a)     DC Equipment:

        From 80% nominal voltage up to 110% nominal voltage (125V for 110V DC supply).

(b)     AC Equipment:

        From 80% nominal voltage up to 110% nominal voltage.

3.1.3    Co-ordination of Transformer Insulation

Nominal system voltage                                  kV        132          66          11

Rated system voltage                                    kV        145          72          12

Assumed highest switching surge                         Not greater than 3:1

Impulse withstand voltage (1.2/50 μs)                   kV        550          325         95

Power Frequency withstand voltage (1 min)               kV        230          140         28

Minimum substation clearances:

(a)      Phase to earth                                 mm        1270         685         200

(b)      Phase to phase                                 mm        1473         786         250

(c)      Between terminal of same phase                 mm        1473         786         250

(d)      Finished Concrete level to base of post        mm        2440         2440        2440

(e)      Section                                        mm        3500         3050        2590

(f)      Height from ground to the nearest              mm        3530         3530        2900
         unscreened live conductor in air


         These clearances are applicable only to equipment not subject to impulse voltage
         tests. They apply for conditions of maximum swing and sag.

3.1.4    Creepage distance of insulators

a)      Nominal voltage between phases             kV           132       66              11
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b)      Minimum external creepage distance           mm         4620        2310        385

The minimum creepage distance measured from the metal cap to the base over the surface
of the insulator shed (expressed in millimetres per unit of nominal voltage between phases)
shall not be less than 35mm per kV (nominal voltage) for outdoor insulators.

The minimum protected creepage distance shall not be less than thirty five per cent of the
total creepage distance. The protected creepage distance refers to that part of the insulator
which is protected against rain at right angles to the axis of the bushing. If the use of "Anti-
fog" or "Anti-pollution" type or other insulators with deep sheds or skirts is intended the
Tenderer shall include a description and fully dimensioned drawing of the insulators in the

3.1.5    Enclosures

All outdoor panels and kiosks and equipment shall have a weatherproof enclosure to
Standard IEC 529 IP54.


The sites are subject to seismic activity and disturbances with a modified Mercalli intensity of
8.0 which should be taken into account in the plant design. For the purpose of design
calculations, the earthquake stresses may be determined on the basis of maximum
horizontal and vertical ground accelerations (seismic coefficient) of 0.15g.

For equipment which will fail by fracture of a brittle component the adopted design stress
using the modified seismic coefficient shall provide for a factor of safety of not less than 2.

The seismic design of the substation equipment shall be based on a recognised design
code, in so far as such codes are applicable to the plant in question. Tenderers shall state
which design code they propose to use.

Tenderers shall include evidence of tests or studies conducted to prove the earthquake
resistance of the equipment offered. Details of equipment similar to that offered and which
has been subject to any serious earthquakes shall be stated.

Calculations to show design factors used, design stresses, seismic response spectra, factors
of safety, inherent damping, mode of failure etc shall be submitted by the Contractor.
Drawings showing the weight and location of the centres of gravity of the principal
components of each piece of equipment, reports of tests and studies conducted to
determine damping factors and natural periods of vibration shall be submitted.


3.2.1    General

Notwithstanding any descriptions, drawings or illustrations which may be submitted with the
Tender, all details will be deemed to be strictly in accordance with the Specification and the
standard specifications and codes referred to therein unless a departure is listed in the
Schedule of Departures and the departure has been formally accepted at the date of
Contract award.
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3.2.2   Contractor's responsibilities

Unless stated specifically to the contrary in the Tender with full supporting explanations, the
Contractor will be deemed to have concurred as a practical manufacturer with the design
and layout of the Works as being sufficient to ensure reliability and safety in operation,
freedom from undue stresses and satisfactory performance in all other essentials as a
working plant.

The Contractor is to include the whole of the Works which are described in or implied by the
Contract Document. All matters omitted from the Contract Document, which may be inferred
to be obviously necessary for the efficiency, stability and completion of the Works, shall be
deemed to be included in the Contract Price.

Works shown upon the drawings and not mentioned or described in the Specification and
Works described in the Specification and not shown on the drawings will nevertheless be
held to be included in this Contract and their execution is to be covered by the Contract Price
in the same manner as if they have been expressly shown upon the drawings and described
in the Specification.

3.2.3   Design and construction

In complying with the requirements of the Specification, both with respect to arrangement
and detail, design is to conform to the best current engineering practice. Each of the several
parts of the Plant is to be of the maker's standard design provided that this design is in
general accordance with the Specification. All systems and equipment supplied shall have
proved satisfactory on other installations when operated similarly in a similar environment.

The Contract Works shall be designed to facilitate inspection, cleaning and repairs and for
operation in which continuity of service is the first consideration. All apparatus shall be
designed to ensure satisfactory operation under the atmospheric conditions prevailing at the
sites and under such sudden variations of load and voltage as may be met under working
conditions on the system and short circuits, including those due to faulty synchronising,
within the rating of the apparatus.

The design shall incorporate every reasonable precaution and provision for the safety of all
those concerned in the operation and maintenance of the Contract Works and of associated
works supplied under other Contracts.

The essence of design should be simplicity and reliability in order to give long continuous
service with high economy and low maintenance cost. Particular attention should be paid to
internal and external access in order to facilitate inspection, cleaning and maintenance.

The design, dimensions and materials of all parts are to be such that they will not suffer
damage as a result of stresses under the most severe service conditions.

Fully detailed specifications of the several parts of the Plant are to be submitted describing
particularly the materials to be used.

The materials used in the construction of the Plant are to be of the highest quality and
selected particularly to meet the duties required of them. Mechanisms are to be constructed
to avoid sticking due to rust or corrosion.

Workmanship and general finish are to be of the highest class throughout.
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Corresponding parts throughout the Contract plant shall be interchangeable and all spare
parts must fit in place accurately without additional machining. When required by the
Engineer, the Contractor shall demonstrate this quality.

All equipment is to operate without undue vibration and with the least possible amount of
noise and is not to cause a nuisance.

All equipment is to be designed to minimise the risk of fire and any damage which may be
caused in the event of fire.

All apparatus shall be designed to obviate the risk of accidental short-circuit due to animals,
birds and vermin. Openings in ventilated enclosures shall be so constructed to prevent the
entry of vermin and insects. The use of materials which may be liable to attack by termites
or other insects is to be avoided.


The Contractor shall design in "The International System of Units" (SI Units) in accordance
with BSI/PD5686, BS 5555 and the Units of Measurement Regulations 1976, SI 1976 No.

Where plant and equipment designs already exist in Imperial units, dimensions and
tolerances of layouts and terminal points shall be presented in SI Units to a degree of
accuracy of conversion from the original unit which permits precise matching with mating

Contract drawings produced specifically for this Contract and plant manuals shall be in SI

SI Units shall be used in all correspondence, technical schedules and in the Operating
Maintenance Instructions.

3.4     DRAWINGS

3.4.1    General

Drawings shall be prepared in accordance with British Standards Specifications BS 308 or in
the event to equivalent Standards of the country of origin subject to the approval of the
Engineer. All drawings shall be on ISO 216 using the preferred "A" series size sheets with
multiple sheets of the same drawing all the same size. The maximum dimensions in one
direction shall not exceed 420 mm and the minimum drawing size shall not be less than 21O
mm x 297 mm. Drawings shall be specifically prepared for this Contract unless existing
standard drawings are approved by the Engineer.

3.4.2    Tender Drawings

The Tender shall be accompanied by the drawings and performance curves referred to in
the Schedules and any other drawings necessary to describe the plant offered.

3.4.3    Manufacturing and Erection Drawings

At the commencement of the Contract, the Contractor shall prepare a register of all drawings
which he proposes to produce which he shall maintain and issue at regular intervals. The
register shall record dates of issue and approval status against each issue. Drawings shall
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be subdivided into groups of drawings in subject matter. The register layout shall be to the
approval of the Engineer.

Before the work is put in hand, dimensioned drawings and diagrams showing all details of
the Plant and materials to be used are to be submitted to the Engineer for approval.

No wiring or connection diagrams shall be submitted for approval unless prior approval has
been obtained for schematic diagrams, which is to include control and protection
schematics, showing the facilities being provided and the working of the schemes. Electrical
schematic diagrams shall show, in a simple manner, the connections between all apparatus
included in the Contract and also those connections to associated equipment which may be
supplied under a separate contract. All schematic drawings shall preferably be submitted on
single drawing on a format large enough to cover the complete system which is the subject
matter of the drawing. All wiring diagrams shall include a schedule of apparatus which shall
explain any symbols or abbreviations used.

All wiring diagrams shall show clearly the details of multicore cables terminated in the
equipment, whether such multicore cables are supplied under the Contract or not.

Wiring diagrams shall be drawn as viewed from the back of the panels. Where wiring
diagrams take the form of schedules, each schedule shall include a view of the back of the
panel with the position of all terminals identified.

Electronic circuit diagrams and component layout drawings are to be supplied in order to
enable full repair and testing by the Purchaser of all electronic equipment supplied under the
Contract. In cases where the Contractor is unable to provide any of the above required
information it should be stated at the time of Tendering.

The drawings are to be submitted as soon as possible after the commencement date and in
any case in sufficient time to permit modifications to be made if such are deemed necessary
by the Engineer without delaying the initial deliveries or the completion of the Contract
Works. The drawings submitted are to be modified as necessary if requested by the
Engineer and re-submitted for final approval.

In no case shall the Contractor proceed with manufacture before the manufacturing
specification, drawings and design data are approved. Comments or approval shall be given
by the Engineer within thirty days from receipt by the Engineer. Any manufacturing work
carried out prior to such approval will be at the Contractor's own risk and expense. The
Contractor's programme shall allow for the time required for the necessary comment and/or
approval by the Engineer.

If the Contractor requires urgent approval of any drawing in order to avoid delay in the
delivery of the Contract Works, he is to advise the Engineer to such effect when submitting
the drawing. The Engineer will not be held responsible if he is unable to approve or
comment on the submitted drawing within the time requested by the Contractor.

If the Engineer fails to approve or comment on the drawings submitted by the Contractor
within the specified period the Contractor may, after advising the Engineer in writing,
proceed with manufacturing at the manufacturer's works in accordance with the programme.

Two full size copies of each drawing, diagram or report shall be furnished for approval of the
Engineer, by air mail if from another country. Within thirty days after receipt the Engineer
will advise the Contractor by air mail in one of the following ways:-
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(a)     "Approved - Category I

(b)     "Approved Except as Noted" - Category II

(c)     "Modification required" - Category III

(d)     "For information only, no approval required" - Category IV.

The notation "Approved" and "Approved Except as Noted" authorise the Contractor to
proceed with fabrication of the plant covered by the drawings subject to the agreed
amendments, if any, indicated.

When the Contractor receives the advice that a plant drawing is "Approved" by the Engineer,
he must then forward within 14 days two copies of this drawing directly to the Engineer.
When the Contractor receives the advice "Approved Except As Noted" the Contractor may
either re-submit a modified drawing for approval or accept the noted modification and
forward within 14 days two copies, suitably amended as above.

No examination or consideration by the Engineer of proposals, drawings or documents
submitted by the Contractor for the approval of the Engineer, nor the approval expressed by
him with regard thereto, either with or without modifications, shall absolve the Contractor
from any responsibility or liability imposed upon him by any of the provisions of the Contract

3.4.4   Numbering of Drawings

All drawings shall bear a title in English, including the site and description of the drawing
subject and the serial number of the Main Contract, the revision letter, the scale, an
indication of the method of drawing, together with an approved Contract Reference.

The title block shall include a space in a prominent location of the Purchaser's name
ELECTRICITY AUTHORITY OF CYPRUS, substation site, Contract No. and drawing
number. A blank area of l00 mm x 7O mm shall be left on all drawings above the title block
for the Engineer's acceptance stamp.

Amended or redrawn drawings shall have the revision letter inserted in each drawing in a
table which shall also include a brief description of the revision, date and authorisation

The drawing title block shall be subject to the Engineer's approval.

3.4.5   Contract Drawings

After all items of Plant have been manufactured one electronic copy of each drawing being
fully revised and previously approved is to be provided together with one reproducible on
heavy gauge polyester base film or similar.

Translucent copies shall be of a base material with a matt finish on both sides and which is
non-tintent polyester plastic between 0.075mm and 0.125mm thick having a non-sensitized
surface suitable for pencil or ink drafting work. They shall be reverse reading (i.e. the image
of the original shall be in contact with the sensitised coating of the copy material during
exposure). If diazo film is supplied it shall be of the ultra-violet stabilised type.
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Within one month of acceptance of the Tender, the Contractor is to forward to the Engineer
a chart detailing the Plant design manufacture, testing and delivery programme for the
complete contract work for his comment or approval. Copies of the approved chart, as
required by the Engineer, are to be provided by the Contractor.

The chart is to indicate the various phases of work for all items of the Contract from the
commencement of the Contract to its final completion, e.g., design, production of drawings,
ordering of materials, manufacture, testing, packing, and delivery.

The works programme shall take into consideration work carried out by different parties
involved and shall define the times at which the various operations controlling the progress
will take place such as submission of drawings, supply of necessary materials etc.


3.6.1      Purpose

The purpose of the manual is to collect all information necessary to allow the purchaser:

          to understand the operation of the equipment,

          to operate it under normal and accident conditions,

          to maintain it under satisfactory conditions,

          to carry out all operations which may be necessary for the maintenance necessary in
           case of incident or accident.

3.6.2      Contents

The details are to cover the main plant and all associated ancillary equipment as supplied
under the Contract. It will not be sufficient to incorporate manufacturer's standard brochures
as part of the text unless they refer particularly to the equipment supplied and are free of
extraneous matter.

The instruction manuals shall conform to the following format:

     Index:

          The index system shall provide rapid and easy access to particular subjects,
           drawings and illustrations. It should include a master index and a sub-index to each
           main section of the manual.

     Description

          This section shall include basic data on the Plant:

              Descriptions of the Plant both for individual items and for the system into which
               items are assembled.
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           Drawings sufficient for the understanding of descriptions.

           Flow sheets or single line and block diagrams which explain the functioning and
            logic of the system. Where related systems are shown on composite diagrams,
            individual systems shall be identified by colour, or coding as agreed.

           Schedules which provide assembled references to items of a like kind, e.g. Valve
            Schedules, Piping Schedules, Operational Limit Schedule, etc.

           Data sheets which assemble in a concise format relevant technical details of a
            plant item or system. The purpose of a data sheet is to provide quick reference
            to the essential facts omitting all reference to general descriptions operating or
            maintenance principles and instructions.

   Installation:

       It shall include installation drawings and step by step procedures for installation.

   Operation.

       This section shall include basic step by step instructions on how to operate the Plant
        both with regard to individual items and to systems under all patterns of normal and
        abnormal conditions. The instructions shall include reference to the applicable
        operation limits.

   Maintenance.

       This section shall comprise the maintenance procedures for the items of the Plant
        and shall include:

           The step-by-step procedures for maintenance including assembly and
            disassembly instructions.

           The checks to be made, including the limits of fits and other tolerances.

           A fault diagnosis guide, where appropriate in particular where it concerns
            electronic equipment.

           The spares required.

           The special tools required.

           Drawings sufficient to illustrate the maintenance procedures, spares and special
            tools including where appropriate exploded views and isometrics to give
            maximum instructional content. The necessary electronic circuit diagrams and
            component layout drawings for all electronic equipment supplied should be
            provided in order to enable full testing and repair of such equipment.

           Lubricant schedule.

           Ball and roller bearing schedule.
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3.6.3    Manual Presentation

Drawings and diagrams shall wherever practicable be reduced to a convenient size and
bound into the manual. The reduced size drawings and diagrams shall be completely legible
and suitable for reproduction. Drawings which are referred to several times in the text shall
be either of the "throw clear" type or be repeated as necessary. Throw-clear drawings are to
be included at the back of the relevant sub-sections, and their locations noted in the Section
drawing index. Detailed engineering drawings necessary for maintenance and mentioned in
the text but not included in the manual because of size reduction difficulties, should
nevertheless be listed in the drawing index, the words 'NOT INCLUDED' being entered
against them. Drawings are to be identified at the bottom right corner by title and number.

The name of the main Contractor, but not that of any Sub-Contractor, may also be inscribed
upon the cover after the description of the Plant.

The name of the Purchaser and substation or other identification followed by a classification
of the plant (e.g., 132/66kV AUTO-TRANSFORMER) is to be inscribed upon the spine of the
cover and, if the instructions are contained in several books, these are to be marked with the
appropriate volume number.

Copies of the draft composite maintenance and operating manuals covering all plant
supplied under the contract shall be submitted to the Engineer at least two months before
the earliest delivery of plant, in accordance with the general clauses of the Specification.
Where appropriate these shall be subdivided to cover each substation site.

In the event that amendments or alterations to the draft manual are required by the
Engineer, the Contractor shall submit revisions for approval without delay so that the final
document can be supplied within the date specified.

Not later than the time of delivery of any Plant covered by the Contract at least three copies
of the approved version of the instructions incorporating amendments required by the
Engineer shall be delivered to the Purchaser. Where more than one substation is covered
by the Contract, at least three sets shall be supplied for each substation.


The recommendations of BS.1133 Packaging Code are to be observed.

Packing shall be such that it affords adequate protection to the enclosed materials against
mechanical damage during transport to its final destination, including any transition during
shipment. All plant shall be packed suitable for open storage for upto three months following
arrival in Cyprus, if required, taking into consideration high humidity and salty atmosphere.

A maximum amount of shop assembly consistent with export shipping requirements is
required in order to reduce field erection work.

Where shipment by container is intended the packing requirements stated below for non-
containerised shipments shall apply for any part container loads.

Containers shall be of the fully enclosed weatherproof type (i.e. metal sides and roof) unless
the size of plant to be shipped necessitates otherwise in which case the type of container
and method of shipping shall be subject to approval.
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For non-container shipments packing shall be stout close-boarded wooden cases of
adequate thickness, suitably braced and banded and lined internally with water-resistant

Certain types of outdoor equipment may be crated, provided that adequate protection of
vulnerable parts is assured. All pipe flanges shall be fitted with wooden covers not less than
4O mm larger in diameter than the flange. These shall be wired or bolted provided that the
ends are adequately protected and the enclosing bands or wires are robust.

For full container shipments a degree of crating may still be required depending on the type
of equipment involved and the Contractor shall state his intentions and obtain approval.

Adequate battens and braces shall be provided to prevent movement of equipment within
the container. Where appropriate due to the weight or nature of the equipment pallet type
bases shall be provided to assist in loading and off loading.

Indoor electrical equipment, whether shipped in containers or packing cases, must be
enclosed in welded polythene envelopes inside the packing cases. The envelopes should be
sealed and have sufficient desiccant inside to absorb the initial moisture content plus an
allowance for leakage.

When in cases or crates or containers, all items shall be so secured that they are not free to
move and cannot work loose in transport. If rotating parts are shipped within their bearings
or mountings they must be adequately braced and restrained to prevent relative movement.
Bags of loose items shall be placed in a supplementary case, each bag having stitched on to
it a metal label indicating the number and nature of its contents. Where a filler material is
used in a case to restrict movement or provide additional protection it must be inorganic and

All surfaces liable to corrosion shall be thoroughly cleaned and special steps, adapted to the
nature of the materials and the time interval between packing and unpacking, shall be taken
to prevent corrosion. These steps may constitute the greasing of surfaces, the application of
a protective coat; enclosure of the items in a hermetically sealed container, consisting of
paper, cellophane, plastic or zinc; the addition of vapour phase inhibitor paper to the
package; or other approved means.

Steps shall be taken to ensure that insulated materials cannot be damaged by moisture,
mould, insects or rodents. Items that include materials liable to be damaged by moisture
shall be packed in hermetically sealed containers in which silica gel, or some other approved
dehydrant, has been inserted.

Cases shall be marked both with large lettering to show which side up the case is to be, and,
if the contents are fragile, marked "FRAGILE" in large letters and the international wine glass
symbol. In the case of container shipments individual crates or equipment on pallets shall
also indicate any special handling or movement requirements or weight limitations.
Packages shall be marked with their place of destination in such a way that rough handling
or the effect of weather cannot remove or obliterate the marking. Each separate package
shall be marked with the gross weight and for all lifts over two tons marks on the cases or
equipment shall show where the weight is bearing and the correct positions for the slings.

The cases shall, whenever possible, be so packed that they can safely be placed any side
uppermost and no reliance shall be placed on the ability of those who will handle the case to
read written instructions or to understand pictorial ones. Cases that have to be slung in a
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certain way shall, as far as possible, be so constructed that they cannot conveniently be
slung in any other way and packages shall preferably be so large that they cannot be easily
rolled over or thrown about; thus when practicable small cases shall be crated together to
form one larger unit. Crates shall be sufficiently strong to be capable of being slung from the
outside even when provision is also made for slings to be attached direct to a major article
inside. Special steps shall be taken to guard against theft during transport. No small items,
such as padlocks, nameplates and so forth, which could be torn off or unscrewed, shall be
accessible. Cases, crates, barrels and drums shall be handed in such a manner as to
obstruct the theft of any of the timber used for packaging, and the bands shall be so secured
that they are not rendered ineffective by shrinkage of the wood.

The materials for each substation should be packed separately and suitable markings to the
approval of the Engineer shall be made on all cases, cratings etc. to distinguish the materials
for each substation.

A descriptive and fully itemised list shall be prepared of the contents of each packing case or
container. A copy of this list shall be placed in a waterproof envelope under a metal or other
suitable plate securely fastened to the outside of one end of the case or container and its
position adequately indicated by stencilling. Where appropriate drawings showing the
erection marking instructions of the items concerned shall be placed inside the case or with
the equipment in the container.

All stencilled markings on cases and crates, or other markings on descriptive metal tabs
fixed to cable drums, bundles of structural steelwork and so forth, shall be applied in two
places with a material which cannot wash off and shall be additional to any erection of other
marks or impressions which may be specified elsewhere.

Components accessories or materials not included in the main shipment as a result of an
oversight or the negligence of the Contractor, shall, unless otherwise agreed by the
Purchaser, be shipped by air mail or air freight on the Contractor's expense.


All plant requiring erection at site shall be marked with distinguishing numbers and/or letters
corresponding to those on the approved drawings and material lists or shipping documents.
All erection marks shall be legible and clearly visible, where relevant erection Marks shall be
stamped before galvanising.

Colour banding to an approved code is to be employed to identify members of similar shape
or type but of differing strengths of grades.


All iron and steel structures shall be protected against corrosion in accordance with BS.5493
and shall withstand the environment for at least 10 years without maintenance.

The Tenderer is to submit with his offer details of painting and finishing covering the extent
of surface treatment required on items in works and prior to despatch.

Before painting or filling with oil, gas or compound all ungalvanised parts including tanks and
accessories, shall be thoroughly cleaned free from rust, scale, burrs, sharp corners, grease
and moisture by shot blasting, pickling and rinsing or other approved process. Any protective
coatings are to be applied after tests have been carried out.
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Pickling shall be preceded by suitable solvent or alkaline cleaning for removal of deposits of
oil, grease etc. where necessary. The finished surface shall be in a suitable condition to
provide good adhesion properties to the primary coat.

Pipes, valves and other similar parts of the Plant which are subject to hydraulic test and are
not readily accessible for drying out are on completion of tests at the manufacturer's works
to be drained out by washing with an approved de-watering oil prior to protection for

All surfaces shall be prepared for coating in accordance with BS.2569.

All paint is to have appropriate standard finish, requiring at least two finishing coats on
prepared surfaces properly filled in to provide a smooth finish. The insides of control
cubicles, cabinets etc., where condensation is liable to occur are to receive the same
number of coats.

All bright metal parts are to be covered before shipment with an approved protective
compound and protected adequately during shipment to Site. After erection these parts are
to be cleaned with correct solvent and polished bright where required.

The Contractor shall provide an adequate supply of touch-up paint for making good minor
damages which may occur during transport.

The colour and shade of all painted external surfaces shall be to BS 38lC colour, 63l Light
Grey or similar (RAL 7035). All internal surfaces which require painting, shall be white.

Instrument, relay and ancillary panel mounted equipment shall be consistently finished and
details submitted for approval by the Engineer.

Colours of equipment other than above and all shades are to be proposed by Contractor and
agreed with the Engineer.


Each main and auxiliary item of plant is to have attached to it in a conspicuous position, a
rating plate of incorrodible material upon which is to be engraved any identifying name, type
or serial number, together with details of loading conditions under which the item of Plant in
question has been designed to operate, and such diagram plates as may be required by the
Engineer. Where labels are provided for making clear the method of operation of
apparatus they shall be concise and preferably diagrammatic in form. Danger labels and fire
protection equipment labels shall be fitted in appropriate places. All labels shall be
submitted for approval and shall be in English unless otherwise specified.

Equipment rating plates and serial numbers shall be located in a conspicuous and easily
readable position.

All equipment shall be clearly and permanently identified with circuit designation front and
rear, number plates and phase discs of appropriate colours.

Labels, number plates and their fixing screws for outdoor use shall be of stainless steel or
other corrosion resistant material. Where the use of vitreous enamelled labels is approved,
the whole surface including the back and edges shall be properly covered and protective
washers shall be provided front and back on the fixing screws.
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Danger notices shall have red lettering on a white background or they may be pictorial if
approved by the Engineer. All other labels and number plates shall have black lettering on a
white background.

               Equipment                            Label Size              Lettering
                                                      (mm)                    (mm)
Main labels on panels, cubicles, kiosks,             125X50                  20X1.5
junction and control boxes and similar
Control and changeover switches and                   70X30                  12X1.5
similar items
Fuses and links                                       35X15                    5X1
Relays and contactors                                 60X20                    5X1
3.11 LOCKS

Padlocks or other approved locking devices for control switches, screened enclosures and
other equipment shall be supplied under this Contract.

On electrical plant at all voltage levels switches on the local and remote control and
protection panels shall be locked as follows:

Control Switches                   -       cylinder or fixed interference lock : key removable
                                           in neutral position only
Discrepancy Switch                 -    fixed interference lock : key removable in neutral
                                        position only
Control Selector Switch           -     cylinder or fixed interference lock : key removable in
                                        each position
Where locks are called for under this Specification, these shall be of an approved dead latch
type, or padlocks as appropriate. Three keys shall be supplied for each lock and all locks
and keys shall be non-interchangeable.

Where a set of locks is provided under any particular section of the Plant, a group master
key shall be supplied in addition.

All locks and padlocks shall be of brass and where they are fitted to switchboards or similar
cubicles shall have the visible parts chromium plated.

Keys and locks shall be impressed with the manufacturer's serial number.

The padlocks and keys shall be engraved with an agreed identifying code or inscription.


In choosing materials and their finishes, due regard is to be given to the humid conditions
under which equipment is to work. Some relaxation of the following provisions may be
permitted where equipment is hermeticallly sealed but it is preferred that tropical grade
materials should be used wherever possible.

   Metals:
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       Iron and steel are generally to be painted or galvanised as appropriate. Indoor parts
        may alternatively have chromium or copper-nickel plating or other approved
        protective finish. Small iron and steel parts (other than rustless steel) of all
        instruments and electrical equipment, the cores of electromagnets and the metal
        parts of relays and mechanisms are to be treated in an approved manner to prevent

   Screws, Nuts, Springs, etc:

       The use of iron and steel is to be avoided in instruments and electrical relays
        wherever possible. Steel screws are to be zinc, cadmium or chromium plated, or
        when plating is not possible owing to tolerance limitations, are to be of
        corrosion-resisting steel. Instrument screws (except those forming part of a magnetic
        circuit) are to be of brass or bronze. Springs are to be of non-rusting material, e.g.,
        phosphor-bronze or nickel silver, as far as possible.

   Rubbers:

       Neoprene and similar synthetic compounds, not subject to deterioration due to the
        climatic conditions, are to be used for gaskets, sealing rings, diaphragms, etc.


Nuts and bolts for incorporation in the plant are preferably to conform to ISO Metric Coarse
to BS.3643, BS.3692 and BS.4190. Other sizes or threads are permitted for threaded parts
not to be disturbed in normal use or maintenance. Where the Contract includes nuts and
bolts of different standards, then the tools to be provided in accordance with this
Specification are to include spanners, taps and dies for these nuts and bolts.

Fitted bolts are to be a driving fit in the reamed holes they occupy, are to have the screwed
portion of a diameter such that it will not be damaged in driving and are to be marked in a
conspicuous position to ensure correct assembly at Site.

On outdoor equipment all bolts, nuts and washers shall be of non-corroding materials where
they are in contact with non-ferrous parts in conductor clamps and fittings and elsewhere
where specifically required by the Engineer.

All washers are to be included under this Contract, including locking devices and
anti-vibration arrangements, which are to be subject to the approval of the Engineer. Taper
washers are to be fitted where necessary.

Where there is risk of corrosion, bolts and studs are to be finished flush with the surface of
the nuts.


Rivets are to conform to the appropriate British Standard and for general use pan heads are
preferred. Rivets on bearing surfaces are to be flat counter-sunk, driven flush. Whenever
practicable, rivetting is to be done by hydraulic tools and rivets must completely fill the holes
when closed. If loose, or if the heads are badly formed, cracked or eccentric to the shank or
do not bear truly on the plate or bar, such rivets are to be cut out and replaced. All surfaces
to be rivetted must be in close contact throughout.
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All important forgings are to be jointly examined at the maker's works by the Engineer and
by a representative of the Contractor during forging and heat treatment and are to be
examined by the latest methods for the detection of defects.


All castings are to be as free from blowholes, flaws and cracks as is practicable. No
welding, filling or plugging of defective parts is to be done without the sanction of the
Engineer and then only with his approval in writing.

All cast-iron is to be of close-grained quality and is to be corrosion-resistant for those parts in
contact with sea water. Cast-iron is not to be used for any part of the equipment which is in
tension or which is subject to impact stresses. This clause is not intended to prohibit the use
of suitable grades of cast-iron for parts where service experience has shown it to be


Where fabrication welds are liable to be highly stressed, the welders or welding operators
shall be qualified in accordance with the requirements of the appropriate section of BS.4872
Part 1, or other relevant British Standard Specification.

The Engineer reserves the right to visit the Contractor's Works at any reasonable time
during the fabrication of the items of Plant and to familiarise himself with the progress made
and the quality of the work to date.

All tests are to be carried out in accordance with the relevant British or other approved
Standards. Where required by the Engineer, non-destructive examination of the finished
weld is to be made. If the examinations be by radiograph means, then the recommendations
of BS.2600 or 2910 where applicable are to be followed and the resulting negatives are to be
made available to the Engineer.


All materials to be galvanised are to be of the full dimensions shown or specified and all
punching, cutting, drilling, screw tapping and the removal of burns is to be completed before
the galvanising process commences.

All galvanising is to be done by the hot dip process with spelter, not less than 98% of which
must be pure zinc and in accordance with BS.729 or BS.443 as applicable. No alternative
process is to be used without the approval of the Engineer. Bolts are to be completely
galvanised including the threads, but the threads are to be left uncoated in the case of nuts.

The zinc coating is to be uniform, clean, smooth and as free from spangle as possible.

Unless otherwise specified the average thickness of zinc coating for iron and steel articles
shall be in accordance with BS729 and that for steel wires to BS443. The Engineer may
select for test as many components to be weighed after pickling and before and after
galvanising as he may think fit.

All galvanised parts are to be protected from injury to the zinc coating due to abrasion during
periods of transit, storage and erection.
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The chromium plating of those components of the Plant where specified and where offered
by the Contractor is to comply with the requirements of BS.1224.


3.20.1 Internal Cleaning of Pipes

The Contractor is to be responsible for ensuring that the internal surface of all pipe lines is
thoroughly clean both during erection and before the pipe line is placed in commission.

The procedure adopted by the Contractor is to include the following:

   Thorough cleaning of all internal surfaces prior to erection to remove accumulations of dirt,
    rust, scale, etc., and welding slag due to site welding before erection.

   Thorough cleaning of all pipework after erection by blowing through to atmosphere to
    ensure that no extraneous matter is left in the system.

3.20.2 Pipework

   All pipework shall be designed for the appropriate conditions and shall comply with
    requirements of the latest Standard. All pipes, bends and tees shall be truly cylindrical and
    uniform in section. The pipes shall be of appropriate approved material, shall be seamless
    and shall be suitable to withstand the stresses and strain involved in the operation of the

Branches shall be welded onto the pipes in an approved manner - alternatively cast steel tees
may be provided subject to the approval of the Engineer. Cast steel tees bends or fittings shall
be of similar analysis to the adjoining pipes.

Care shall be taken that the internal diameter of all castings is the same as that of the pipes to
which they are joined. Castings without ample fillets at the points of attachment of flanges and
branches will be rejected.

All pipes shall be adequately anchored and expansion loops and bends shall be provided
where required and shall preferably be arranged horizontally. The Contractor will be
responsible for the design and positioning of all provisions for expansion.

All piping systems shall be arranged to allow adequate falls in the direction of the flow except
where otherwise approved by the Engineer.

Adequate provision shall be made for air release, pressure relief, and drainage on all pipework.
Isolating valves, complete with padlocks and hose connections, shall be provided at the take
off points of all such drains.

Special care shall be taken to ensure that no permanent stresses are set up in any pipeline or
items of connected plant when closing lengths are jointed.

Except where otherwise specified all piping shall have full penetration butt welded connections
with a minimum number of flanged joints necessary for maintenance.
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All terminal points and at points where castings adjoin and where, in the opinion of the
Engineer, it is undesirable to use a butt-welded joint, a flanged joint of approved design shall
be provided.

Pipes and attachments shall be properly aligned and jigged prior to welding. If tack welds are
used the tacks shall be fused into the first runs of weld deposited.

All flanged joints and bolting materials shall be liberally smeared with an adequate graphite
solution during erection and/or assembly to assist subsequent maintenance.

Gauges shall not be mounted directly on the pipes but shall be secured to a structure which is
free from vibration.

3.20.3 Pipe Supports

The whole of the pipework and accessories included in this Contract are to be supported and
mounted in an approved manner. All necessary slings, saddles, structural steelwork,
foundation bolts, fixing bolts and all other attachments are to be provided.

Supports shall be arranged so that any valve or fitting can be withdrawn without any additional
support being required and without disturbing the rest of the plant.

No pipe shall be supported from another pipe.

The number and positions of all supports and the maximum weight carried by a support is to
be subject to the approval of the Engineer.

3.20.4 Valves

All valves shall be of approved design and manufacture. Where valves are of a similar make,
size and type they shall be interchangeable with one another. Valves shall have bolted
connections. Light pattern valves are not acceptable for any service.

All valves shall be of the fullway gate type unless otherwise specified and when in full open
position, the bore of the valve shall not be obstructed by any part of the gate. The internal
diameter of all valves at the ends adjacent to the pipework shall be similar to the internal
diameter of the connecting pipework.

All valves over 5O mm nominal bore shall have outside screwed spindles, the screwed thread
on the spindle shall not pass through or into the stuffing box. Where valves are exposed to the
weather, protective covers shall be provided for the spindles which shall be to the approval of
the Engineer.

All valves shall be closed by rotating the handwheel in a clockwise direction when looking at
the face of the handwheel. The face of each valve handwheel shall be clearly marked with the
words "OPEN" and "SHUT" and with arrows adjacent to indicate the direction of rotation to
which each refers.

All valves over 5O mm bore shall have indicators to show readily whether the valves are open
or shut. In the case of valves with extended spindles, indicators shall be fitted to both the valve
spindle and the operating pedestal.

Each valve handwheel shall have fitted firmly in position on top of the handwheel, a permanent
stainless steel nameplate with inscribed lettering to indicate the system with which the valve is
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associated and an identification number corresponding to the number allocated to the valve on
the system flow diagram. The identification system shall be to the approval of the Engineer.

Valves shall be installed with their spindles above or at the horizontal position, no valves shall
be erected in the inverted position. Hand operated valves shall be easily operable by one man.

Adequate means of easy lubrication shall be provided for all valves and operating extension

All valves up to and including 75mm bore shall be made of gunmetal.

Cast iron shall not be used in the manufacture of any valves. Plastic or composition
handwheels will not be accepted.

All non-return valves shall be of an approved type and manufacture and head loss through the
valves shall be to approval. The bodies shall be provided with removable access covers to
enable the internal parts to be examined or renewed without removing the valve from the
pipeline. The bodies shall be stamped with an arrow to indicate the correct flow direction.

Non-return valves shall not be fitted in vertical pipe runs.

Valves which it will be necessary to lock in the open or closed position are to be provided with a
non-detachable locking arrangement by locking pins which shall be of an antirattle design so
as not to add to noise emission. Such locking pins shall incorporate 8mm holes for padlocks.

Filter valves shall be fitted with locking plates.


All joints of fabricated oil or compound filled chambers, other than those which have to be
broken, are to be welded and care is to be taken to ensure that the chambers are oil-tight.
Defective welded joints are not to be caulked but may be re-welded subject to the written
approval of the Engineer.

Suitable provision is to be made for the expansion of the filling medium in all oil or compound
filled chambers and the chambers are to be designed to avoid the trapping of air or gases
during the filling process.

Design shall permit the temperature of any chamber which is to be compound filled to be
raised such that the compound does not solidify during the filling process.

All wiring in the vicinity of oil-filled chambers is to be insulated with oil-resisting insulation of
approved quality.


Oil level indicators of approved design are to be fitted to all oil containers. The indicators are to
show the level at all temperatures likely to be experienced in service, are to be marked with the
normal level at 20oC clearly visible from normal access levels and are to be easily dismantled
for cleaning. In addition, the normal filling level of all removable containers is to be marked on
the inside.
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Pressure gauges are to comply with the requirements of BS.1780.

All pressure gauges are to be fitted with stop cocks immediately adjacent to each gauge and
all pressure gauge piping is to be fitted with an isolating valve at each point of connection to the
main system. Where pressure gauges are mounted on panels, the stop cocks are to be
suitable for the connection of a test gauge.

Where a difference in level exists between the situation of the gauge and the point at which
pressure is to be measured, appropriate compensation is to be made in the dial reading and
the dial must be marked with the amount of compensation applied. Where the compensation
would amount to two percent or less of the total movement indicated under normal conditions,
it may be ignored.

All pressure gauges are to be clearly identified by means of labels of approved type and

All pressure gauge piping is to be of corrosion resistant steel or copper tube.


All wiring shall be neatly run and securely fixed in cleats, bunched in neat forms or run in
approved wiring troughs or non-corrodible tubes. The number of wires in any one bunch or
tube shall not exceed 20 and the duct filling ratio shall not exceed 75%. The practice of
doubling back wires on themselves in a trough to absorb slack is not acceptable. Where
bunched or handled wires are run in troughs the maximum number in each bunch or bundle
shall be retained at 20.

Cleats shall be of moulded or metal-reinforces insulating material and shall be of the limited
compression type. Insulated strapping shall be used for bunched wires. Wiring troughs shall
be of insulating material.

Wherever practicable, wiring shall be accommodated on the sides of the cubicles and the wires
for each circuit shall be separately grouped. Back of panel wiring shall be so arranged that
access to the connecting stems of relays and other apparatus and to contacts of control and
other switches is not impeded. Where provision is made for addition of equipment not required
initially, means shall be adopted for supporting and termination wiring during the interim period.

Except where terminals are approved by the Engineer for use with bare conductors, crimped
connectors of approved type are to be used to terminate all small wiring.

All wiring shall have insulation incapable of supporting combustion. Cores shall be multi-

The size of wiring cores shall be selected with due regard to thermal requirements, voltage
drop and mechanical strength.

Particular attention is to be paid to fatigue failure of cores due to flexing or vibration including
damage at terminations which require disconnection for test purposes.

All panel wiring is to comply with the requirements of BS.6231, Type A or B, as appropriate.
Conductors are to be copper and have a cross section equivalent to 30/0.25mm (1.5mm2),
50/0.25mm (2.5mm2), 7/0.67mm (2.5mm2) or 1/1.78mm (2.5mm2) but single stranded
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conductors should only be employed for rigid connections which are not subject to movement
or vibration during shipment, operation or maintenance. Flexible conductors of smaller sizes
shall only be employed with written approval.

Small wiring shall be black or other approved uniform colour unless otherwise specified or
extensions are involved to existing plant which has already coloured wiring, in which case the
existing wire colouring scheme shall be retained as far as existing switchboards are concerned.
For new switchboards the coloured wiring shall comply with the following code:

             Colour of Wire                                 Circuit Particulars

Red      )                               First, second and third phase connections respectively
Yellow   )                               when directly connected to the primary circuit or
Blue     )                               connected to the secondary circuits of current and
                                         voltage transformers.

Green or Green/Yellow                    Connections to earth
Black                                    AC neutral connections, earthed or unearthed,
                                         connected to the secondary circuit of current and
                                         voltage transformers. AC connections other than those
                                         above and connections in AC/DC circuits.

Grey                                     Connections in d.c. circuits.

Alternatively, where equipment is wired in accordance with a manufacturer's standard, wiring
may be carried out in a single colour except that all connections to earth shall be green or

Wiring diagrams must indicate wire colours and are to be drawn as viewed from the back of
the panel.

Numbered ferrules shall be fitted to internal wiring and to all multi-core cable tails.

Ferrule numbering shall be in accordance with the established numbering system for existing
substations. For new substations the Contractor shall submit for approval by the Engineer of a
standard system of numbering for small wiring.

Each wire shall have a letter to denote its function, e.g. control of circuit-breaker, current
transformer for primary protection, voltage for instruments, metering and protection. The
function letter shall be followed by a number identifying the individual wire. Every branch of
any connection shall bear the same identification mark. At points of interconnection where a
change of numbering cannot be avoided double ferrules are to be provided. Where it is
necessary to identify branches which are commoned (e.g. current transformer leads), different
identification marks for the branches may be employed only if they are commoned through
links, or are connected to separate terminals which are then commoned by removable

Numbering shall read from the terminals outwards on all wires.

Unused cores in multicore cables shall be ferruled U1, U2, etc. at both ends and connected to
individual spare terminals.
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Ferrules shall be of white insulating material with glossy finish to minimise adhesion of dirt.
They shall not be affected by damp or oil and shall be clearly and permanently marked in

The ferrules shall be of sleeve type so fitted that they cannot slip along the cable or be
removed from the cable without reterminating.

The ferrules on all wiring directly connected to circuit breaker trip coils, tripping switches, etc.,
are to be of a colour, preferably red, different from that of the remainder and marked "Trip" or
"T" in white.

All wiring shall be taken to terminal boards and wires shall not be teed or jointed between
terminal points.

Electrical wiring and instruments are to be so located that leakage of oil or water cannot affect

Where plastic material is used for ducting etc. it shall be tough and shall be able to resist shock
tests for reinforced enclosure equipment. Inflammation of the plastic due to exposure a flame
shall not propagate beyond the combustion area when the flame is removed.

All metallic cases of instruments, control switches, relays, etc., are to be connected by means
of copper conductors of not less than 2.5 mm section to the nearest earth bar. These
conductors may be bare or have insulation coloured green.


Screw type terminals shall utilise a pressure plate arrangement, single point screw terminations
will not be accepted. The size of screws for screw clamps is not restricted provided that the
screws are captive, otherwise they shall comply with the requirements for bolt and stud
terminals. Not more than two wires shall be connected to any one terminal. Insulating barriers
shall be provided between adjacent pairs of terminals. The height of the barriers and the
spacing of the terminals shall be such as to give adequate protection while allowing easy
access to terminals.

Terminations shall be grouped according to function and labels shall be provided to show the
group function.

Connections to terminals shall be made using preinsulated reinforced crimped end pieces.

Terminals of Tripping circuits shall be of the slide-type test/disconnect type and shall have
facility for inserting banana type testing terminal to both the incoming and to the outgoing

Connections to relays shall be made using screwed lugs clamped to the conductors with an
insulating sleeve.

All terminal boards are to be mounted in accessible positions and, when in enclosed cubicles,
are preferably to be inclined towards the rear doors to give easy access to terminations and to
enable ferrule numbers to be read without difficulty. Spacing of adjacent terminal boards is to
be not less than 100mm and the bottom of each board is to be not less than 200mm above the
incoming cable gland plate. Separate terminations are to be provided on each terminal strip for
the cores of incoming and outgoing cables including all spare cores.
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Acceptable types of terminals are:

       Screw or stud type used with crimped ring type termination. Screws and stud are to be
        not less than size M6 but stainless steel and bronze down to size M5 may be used
        provided that the current carrying capacity is adequate. All studs are to be provided
        with nuts washers and lock washers.

       Insertion clamp type such as the Klippon type SAK6 or the Phoenix type UK10 or
        similar equivalent to the approval of the Engineer, whereby the crimped termination is
        clamped between plates by a screw having a suitable locking device. Terminal entries
        are to be shrouded such that no current carrying metal is exposed. Tapped holes are
        to have not less than three full threads. Screws are to be of plated steel, stainless steel
        or phosphor bronze and size M3 and M4.

Terminal assemblies are preferably to be of the unit form suitable for mounting collectively on a
standard assembly rail, secured from the front and giving the required number of ways plus at
least ten percent extra terminals as spares. Relevant manufacturer's catalogues are to be
supplied with the offer. If requested by the Purchaser samples of terminals are to be provided
for inspection and approval.

For voltages in excess of l25V, circuit terminals are to be segregated from other terminals and
are to be fitted with non-flammable plastic covers to prevent contact with any live parts. They
are to have warning labels, with red lettering, mounted thereon in conspicuous position.

All connections are to be made at the front of the terminal boards and no live metal is to be
exposed at the back.


All insulating materials are to be suitably finished so as to prevent deterioration of their qualities
under the specified working conditions.

Plastics, elastomers, resin-bonded laminates and inorganic materials are to be of suitable
quality selected from the grades or types in the appropriate British Standard.


All necessary studs, connectors and earth bars are to be provided to permit the connection of
each switchboard, motor or other electrical equipment supplied under the Contract to the
substation general earthing system. The provisions for earthing are to be such that no reliance
is to be placed on the conductivity of metal to metal joints without the use of special


All motors are to be in accordance with BS.5000, Part II, or IEC.34 and, unless otherwise
specified shall have cooling type ICO1 suitable for continuous operation and direct on-line

They are to be suitable in all respects for service under the conditions at site. Main conductor
and slot insulation is to be non-hygroscopic and in accordance with Class B of BS.2757.

Motors are to be capable of operating continuously at rated output at any frequency between
48 and 51 cycles per second and at 85% of the nominal voltage without injurious overheating.
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Motors are to be designed to operate for a period of not less than five minutes at a voltage of
25% below the nominal value and at normal frequency without injurious overheating. If
required by the Engineer, the Contractor is to demonstrate that the motors comply with this

Each motor shall be protected by a miniature circuit-breaker or fuses with thermal overcurrent

The starting current at full voltage is not to exceed six times the rated full load current.

Motor bearings are to be of the rolling type and the cage locating the balls or rollers is not to be
in contact with the races. All bearings are to be fitted with oil or grease lubricators. Vertical
shaft motors are to have approved thrust bearings.

The ends of motor windings are to be brought out to terminal boxes and the arrangement is to
be such as to permit easy changing over of any two phase leads.

All terminals are to be of the stud type of adequate size for the particular duty, marked in
accordance with BS.822 and to be enclosed in a weatherproof box, which is to be securely
fixed to the motor frame.

All terminal boxes are to be fitted with an approved sealing chamber, conduit entry or adaptor
plate, as required, together with the necessary fittings to suit the type of cable supplied.

Motors shall be provided with a 9 mm diameter earthing stud and lock nuts. The material
surrounding the stud shall have a flat surface for an area of 3O mm diameter. For motors
below l kW a 6 mm diameter earthing stud may be fitted. Holding down bolts shall not be used
for earthing purposes.

The following protection shall be provided:-

       Motors up to 1 kW:                      fuses, thermal or magnetic overload

       Motors more than 1 kW: fuses:           thermal overload, single-phasing protection


Control switches and pushbuttons shall comply with BS.4794.

3.29.1 General

Where necessary, control switches are to be capable of being locked in appropriate positions.
Such switches are to be controlled by independent springs, the use of contact springs alone for
restoring not being acceptable.

All pushbuttons are to be of the non-retaining type made of non-hygroscopic materials,
non-swelling and fitted to avoid any possibility of sticking.

The contacts of all switches and pushbuttons are to be strong and to have a positive wiping
action when operated.

All control switches are to be provided with labels complying with the requirements of this
Specification in addition to clear indication as to the direction of each operation, for example,
"open", "close" etc.
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3.29.2 Electrical Control Locations:

Equipment may be electrically controlled from a number of different control points as specified
in the appropriate sections of this Specification. The control positions shall be designated as

   Local Control

       Located adjacent to the item of plant to facilitate maintenance, inspection and
        emergency operation.

   Remote Control

       Located at a substation control room where specified items of Plant are monitored and
        controlled by direct wire connection.

   Supervisory Control

       Located at a System Control Centre where principal items of plant at a number of
        substations are remotely controlled via a telecontrol system.


Indicating lamps fitted into the facias of switch and instrument cubicles or panels are to be
adequately ventilated.

Lamps are to be easily removed and replaced from the front of the panel by manual means
preferably not requiring the use of extractors.

The bezel of metal or other approved material holding the lamp glass is to be of an approved
finish and to be easily removable from the body of the fitting so as to permit access to the lamp
and lamp glass.

The lamps are to be clear and are to fit into a standard form of lamp holder. The rated lamp
voltage should be ten percent in excess of the auxiliary supply voltage, whether AC or DC.
Alternatively, low voltage lamps with series resistors will be acceptable.

The lamp glasses shall comply with BS.1376 and BS.4099 and are to be in standard colours,
red, green, blue, white and amber. The colour is to be in the glass and not an applied coating
and the different coloured glasses are not to be interchangeable. Transparent synthetic
materials may be used instead of glass, provided such materials have fast colours and are
completely suitable for use in tropical climates.


Where appropriate, each item of Plant is to be equipped with all necessary auxiliary switches,
contactors and mechanisms for indication, protection, metering, control, interlocking,
supervisory and other services. All auxiliary switches are to be wired up to a terminal board on
the fixed portion of the plant, whether they are in use or not in the first instance.

All auxiliary switches and mechanisms are to be mounted in approved accessible positions
clear of the operating mechanisms and are to be protected in an approved manner. The
contacts of all auxiliary switches are to be strong and to have a positive wiping action when
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Banks of auxiliary switches and associated terminal boards are to be arranged to facilitate
extension when required.


Enclosures for electrical apparatus are to afford the following degrees of protection classified in
IEC.529 (BS.5490).

       Metal housing of switchboard - IP54 - also provision of a thermostatically controlled
        230VAC anti-condensation heater and screened drainage holes.

       Auxiliary switches and associated terminals - IP54 - as (i) but with heater control switch
        common to other apparatus on the same circuit.

       Junction boxes - IP54

       Instruments - IP65

       Motors - IP54

Operating boxes, kiosks, cubicles and similar enclosed compartments forming part of auxiliary
equipment shall be adequately ventilated to minimise condensation. All contactor or relay coils
and other parts shall be suitably protected against corrosion. Anti-condensation heaters of an
approved type shall be provided inside each cubicle or where necessary each cubicle
compartment. They shall be shrouded and located so as not to cause injury to personnel or
damage to equipment. A thermostat shall be arranged to switch off the heater supply when the
ambient temperature exceeds 3O-35oC. Means shall be provided at each unit for isolating the
supply. A common switch with a neon gas type lamp labelled "Cubicle heaters on" shall be
mounted at a convenient point such that it will not require movement in the event of extension
units being added.


Thermometer pockets and instrument connections of an approved pattern are to be fitted in
such positions as may be determined to suit the operation and testing of the plant to the
approval of the Engineer. A thermometer pocket is to be fitted adjacent to each point of
connection for distant remote temperature indication unless specifically stated to the contrary.
Where necessary, the pocket is to be of approved alloy material suitable for the required

All thermometer pockets are to comply with the requirements of BS 2765.

3.34 OIL

The Contractor shall supply the first filling of all oil required for the operation of the plant. The
oil shall be in accordance with IEC.296 or BS:148 uninhibited, non-labelled, Class I and on
testing at works shall comply with these Standards.

All oil or oil derived compounds shall be PCB free. A certificate shall be provided at the tender
stage guaranteeing that none of the equipment offered utilises PCB's and each shipment shall
be accompanied by a certificate confirming that all equipment in the shipment is free from
PCB's. Furthermore, all shipments shall be accompanied by a Material Safety Data Sheet
which shall give the composition, the characteristics and instructions for the correct and safe
use and disposal.
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3.35.1 11kV Cable Boxes

         Cable boxes shall be unfilled and shall have sufficient clearances and be suitable for
          heat shrinkable terminations for the number, type and size of cables specified in the
          Schedule of Requirements.

         Provision shall be made for earthing the body of each cable box.

         Boxes shall be arranged for cables entering vertically from below.

         To provide full accessibility and to enable the cables to be prepared in their final
          position in the cable box, the gland plate and the front cover down to the gland plate
          shall be separate and removable.

         The cable boxes shall be supplied complete with the required connecting bars
          including, any supporting insulators, on which the cable connectors will be attached.

         Where cable boxes are provided for three-core or four-core cables, the sweating
          sockets on the outer phases shall be inclined towards the centre to minimise bending of
          the cable cores.

3.35.2 132kV and/or 66kV Cable Boxes

         The cable boxes shall be suitable to accommodate the cable terminations that shall be
          provided by others. Final drawings of terminations to be used will be submitted to the
          successful tender after the award of the contract.

3.35.3 Cable Glands

         Where lead sheath cables are to be used wiping cable glands to BS 2562 shall be
          provided under the Contract.

         Glands for single core cables are to be insulated from the box. The insulation is to
          include a metallic "island" layer for testing purposes. In addition, removable connectors
          for bonding across the gland insulation are to be provided. The gland insulation is to be
          capable of withstanding a dry high voltage test of 2kV RMS AC for one minute.

         Where XLPE insulated cables are to be used compression type cable glands to B.S.
          6121 shall be provided under the Contract.


4.1       GENERAL

4.1.1     Types of Transformer and Operating Conditions

i)        General:

The transformer shall be of the oil immersed type and suitable for outdoor installation and shall
comply with IEC-76, Parts 1 to 5 inclusive.

ii)       Cooling:
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The types of cooling shall be as stated in the Schedule of Requirements and the letters relating
to the method of oil circulation and cooling used hereafter in the Specification and Schedules
shall be in accordance with IEC-76.

Where a combination of two methods of cooling is applied to one transformer as for
ONAN/ONAF Units, the transformer shall be capable of operating under the ONAN condition
up to half full load or more as stated in the Schedule of Requirements, after which the cooling
equipment is to come into operation and the transformer will operate as an ONAF Unit.

The forced cooled transformer shall be fitted with two coolers or two banks of radiators each
capable of dissipating 50% of the losses at continuous maximum rating. It shall be capable of
remaining in operation at full load for twenty minutes in the event of failure of blowers
associated with both coolers without the calculated winding hot spot temperature exceeding

Failure of one fan in each group of blowers shall not reduce the continuous maximum rating of
the transformer.

iii)    Parallel Operation

The Transformer supplied shall be suitable to operate satisfactorily in parallel with other
transformers of same rating and nominal voltages when operating on the same tap.

4.1.2    Continuous Maximum Rating Basis of kVA Rating

The Transformer shall have on both the High Voltage and the Low Voltage Windings the rating
stated in the Schedule of Requirements and shall comply with the requirements as regards
temperature rise and overloads on all tappings irrespective of the direction of power flow and
with the voltage of the lower voltage winding at the normal voltage stated in the Schedule of

In the case of multi winding units the rating shall permit delivery of the specified loads at the
terminals specified and they shall also comply with the requirements as regards temperature
rise and overloads on all tappings with the voltage of the intermediate voltage winding at the
normal voltage stated in the Schedule of Requirements.

The transformer shall be capable of delivering at all tappings rated currents at an applied
voltage equal to 110% of the tapping voltage (clause 4.4 of IEC 76-1 and B.S 171 refers).

The overload capability shall be in accordance with IEC 354.

The service conditions will be those specified in the Schedule of Requirements. Basis of Voltage Rating

The voltage rating shall be based on the turns ratio, i.e., no load values.

The voltages between phases on the higher and lower voltage windings measured at no load
shall be those corresponding to the normal ratio of transformation stated in the Schedule of
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Means shall be provided for varying the normal ratio of transformation in accordance with the
Schedule of Requirements.

4.1.3   Electrical Connections

Transformer windings shall be connected in accordance with the IEC.76 group symbol
specified in the Schedule of Requirements.

All electrical connections within windings shall be brazed but, subject to approval, mechanically
crimped joints may be used for round stranded conductors on tapping, bushing or earthing
connections and on bundle conductors where design has been proved by type test and
application is subject to rigorous quality control.

4.1.4   Ability to Withstand Short Circuit

i)      General:

The transformer shall be capable of withstanding, on any tapping and without damage the
thermal and dynamic effects of external short circuits under the conditions stated in IEC-76,
Part 5. For this purpose the design short circuit level for each system voltage is stated in
Schedule of Requirements.

ii)     Calculations and Tests:

Evidence shall be submitted with the Tender as to the extent to which the manufacturer has
proved by test the ability of the specified transformer to withstand short circuit.

The Tenderer shall state in the Schedule of Particulars a brief description of the transformer or
parts thereof which have been subjected to short circuit test. It is preferred that this information
relates to designs comparable with the transformer Tendered but in the event this is not so the
Engineer reserves the right to require calculations to prove that the design of transformer
tendered will satisfactorily comply with this Clause.

4.1.5   Stabilising Windings

Unless otherwise specified in the Schedule of Requirements, the product of the number of
turns of the stabilising windings and the cross-sectional area of one such turn must not be less
than 33% of the corresponding product for the untapped main winding.

When required in the Schedule of Requirements, the stabilising winding shall be capable of
carrying continuously the load specified therein.

4.1.6   Losses and Evaluation of Losses

The Tenderer shall state in the Schedule of Particulars guaranteed values for component
losses (i.e. no-load loss, load loss at CMR and auxiliary loss) of the total loss, which shall be as
low as is consistent with transport restrictions, reliability and economic use of materials.

Tenders will be assessed using the following:

Total cost = P + 10.27 (Fe + Cu + Aux)
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P        =       Tender price of transformer in £C

Fe       =       Product of "no-load" loss in KW and £C225

Cu       =       Product of "full load" copper loss in kW and C£ 15

Aux      =       Product of the transformer auxiliaries full load in kW and C£4.-

The acceptance of transformers yielding component losses higher than the guaranteed values
shall be governed by either of the following:

     A. Component losses in excess of guaranteed values but within the tolerance permitted
        under IEC.76, Part 1.

                Transformers shall be acceptable subject to full compliance with all other
                 technical particulars including temperature rise at CMR and subject to the
                 Tenderer accepting deduction from the Contract Price of charges for each KW
                 or part thereof of component losses in excess of the guaranteed values, at the
                 above evaluation rates.

     B. Component losses in excess of guaranteed values and exceeding the tolerance
        permitted under IEC.76, Part 1.

                The acceptance of the transformers shall be entirely at the discretion of the
                 Purchaser and subject to the Tenderer accepting deduction from the Contract
                 Price of charges for each KW or part thereof of component losses in excess of
                 the guaranteed values, at the above loss evaluation rates.

In the event of transformers yielding component and total losses which are either equal to or
below the guaranteed values, the Tenderer will not be entitled to any premium in respect of
reduction in losses below the guaranteed values.

4.1.7   Impedance

The value of reactance measured on all tappings shall be as stated in Schedule of
Requiremetns. The transformers are required to operate in parallel with upto two other similar

4.1.8   Noise

The transformer noise levels shall be measured as a type test and in accordance with IEC-551.
The acceptable mean sound level of the transformers shall be as stated in the Table of Clause

In addition, the transformer noise level shall be measured as a special test, with the
transformer energised at the maximum operating flux density. The acceptable mean sound
level of the transformer shall not exceed 80dB(A) at the worst possible operating conditions.

Where the bottom plate of the transformer tank will be in direct contact with the surface of the
foundation, anti-vibration pads shall be provided under the contract for insertion between the
transformer and its foundation.
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4.1.9    Harmonic Suppression

Transformers shall be designed with particular attention to the suppression of harmonic
voltages, especially the third, fifth and seventh harmonics and minimise the detrimental effects
resulting therefrom.


4.2.1    Magnetic Circuit

The design of the magnetic circuit shall be such as to avoid static discharges, development of
short circuit paths internally or to the earthed clamping structure, and the production of flux
components normal to the plane of the laminations. Each lamination shall be insulated with a
material stable under the action of pressure and hot oil.

The winding structure and major insulation shall be designed to permit an unobstructed flow of
cooling oil through core cooling ducts to ensure efficient core cooling.

The magnetic circuit shall be insulated from all structural parts, and shall be capable of
withstanding a test voltage to core bolts and to the frame of 2,000V RMS for one minute.

4.2.2    Flux Density

Cores shall be constructed from cold rolled grain oriented steel sheets. Design shall be such
that there will be no adverse effects due to core or stray flux heating with the quality of steel
employed, and that when operating under the most onerous conditions envisaged in IEC 76
and IEC 354, flux density in any part of the magnetic circuit does not exceed 19,000 lines per
square centimetre (i.e. 1.9 Tesla). The maximum flux density of the transformers when
operating with rated winding voltage at the principal tap shall not exceed 1,50 Tesla.

The Contractor shall determine the operating conditions under which the maximum flux density
will be attained within the following simultaneously applied limits:

Frequency                   48 Hz
Voltage H.V.                up to but not exceeding the maximum system voltage specified in
                            the Schedule of Requirements.
Load                        The transformers may be subjected to intermittent overloading in
                             accordance with I.E.C. Publication 354 with:

                            Load          : 150% of Rated kVA

                            Power Factor : 0.85 Lagging.

4.2.3    Windings

All transformer windings for 66kV and below shall have uniform insulation as defined in IEC-76.

The transformers shall be designed to withstand the impulse-voltage levels and power
frequency voltage tests specified.

The windings shall be located in a manner which will ensure that they remain electrostatically
balanced and that their magnetic centres remain coincident under all conditions of operation.
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The windings shall also be thoroughly seasoned during manufacture by the application of axial
pressure at a high temperature for such length of time as will ensure that further shrinkage is
unlikely to occur in service.

The windings and leads of the transformer shall be braced to withstand the shocks which may
occur through rough handling and vibration during transport, switching and other transient
service conditions including external short circuit.

If the winding is built up of sections or of disc coils separated by spacers, the clamping
arrangements shall ensure that equal pressures are applied to all columns of spacers.

4.2.4     Internal Earthing

i)       General:

All metal parts of the transformer with the exception of the individual core laminations, core
bolts and associated individual clamping plates shall be maintained at some fixed potential.

ii)      Earthing of Core Clamping Structure:

The top main core clamping structure shall be connected to the tank body by a copper strap.
The bottom main core clamping structure shall be earthed by one or more of the following

       A. By connection through vertical tie rods to the top structure.

       B. By direct metal-to-metal contact with the tank base maintained by the weight of the core
          and windings.

       C. By connection to the top structure on the same side of the core as the main earth
          connection to the tank.

iii)     Earthing of Magnetic Circuits:

The magnetic circuit shall be earthed to the clamping structure at one point only through a
removable link placed in an accessible position just beneath an inspection opening in the tank
cover and which, by disconnection, will enable the insulation between the core and clamping
plates, etc., to be tested at voltages up to 2.0kV. The link shall have no detachable
components and the connection to the link shall be on the same side of the core as the main
earth connection. These requirements are compulsory.

Magnetic circuits having an insulated sectional construction shall be provided with a separate
link for each individual section and the arrangement of the connections shall be subject to the
approval of the Engineer. Where oil ducts or insulated barriers parallel to the plane of the
laminations divide the magnetic circuit into two or more electrically separate parts, the ducts
and insulating barriers which have a thickness greater than 2.5mm are to be bridged with
tinned copper strips so inserted as to maintain electrical continuity.

iv)      Earthing of Coil Clamping Rings:
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Where coil clamping rings are of metal at earth potential, each ring shall be connected to the
adjacent core clamping structure on the same side of the transformer as the main earth

v)      Earthing of stabilising windings:

Where a stabilising winding is provided, one corner of the delta winding shall be earthed
externally by a removable link to the main tank earthing terminal.

vi)     Size of Earthing Connections:

Main earthing connections shall have a cross-sectional area of not less than 80mm2 but
connections inserted between laminations may have cross-sectional areas reduced to 20mm2
when in close thermal contact with the core.

4.3     TANKS

4.3.1    Transformer Tanks

The transformer shall be enclosed in a suitably stiffened welded steel tank such that the
transformer can be lifted and transported without permanent deformation or oil leakage. The
construction shall employ weldable structural steel of an approved grade to BS.4360. Welding
of structural steel shall be to BS.1856.

Lifting lugs shall be provided, suitable for the weight of the transformer, including core and
windings, fittings, and with the tank filled with oil. The tank shall be provided with at least four
jacking pads not less than 350 mm to the transformer foundation, and where required, with
lugs suitably positioned for transport on a beam transporter.

The transformer tank and conservator vessel, when empty of oil, shall be designed to
withstand full vacuum without deflection exceeding the value stated in the Schedule of Tests.
Ancillary apparatus eg tap changers etc need not be so designed if provision can be made not
to subject them to full vacuum during any site processing and their inability not to withstand full
vacuum does not inhibit full vacuum being applied to the tank and conservator vessel.

The transformer tank must be designed and secured to withstand the vibrations from
earthquakes as set out in this Specification including a strengthened base and anchorage of
the core and windings to this base.

Where the design of the tank is such that the bottom plate will be in direct contact with the
surface of the foundations, the plates shall have the following minimum thickness:

Length of Transformer Tank                                        Minimum Thickness

                                                   Side Plates                Bottom Plates

Less than 2500mm                                   6mm                        19mm

Greater than 2500mm                                9mm                        25mm

Greater than 7500mm                                9mm                        32mm

Where skid type bases are provided, the plates shall have the following minimum thicknesses:
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Length of Transformer Tank                                        Minimum Thickness

                                                   Side Plates                Bottom Plates

Less than 2500mm                                   6mm                        9mm

Greater than 2500mm                                9mm                        12mm

The base of the tank shall be so designed that it is possible to move in any direction the
complete transformer unit, full with oil and fitted with all specified fittings, without injury when
using rollers, plates, crane or rails without overstraining any joints and without causing any
subsequent leakage of oil. A design which requires that slide rails be placed in a particular
position is not to be used. Pulling eyes shall be provided at the base of the transformer for
enabling skidding of the transformer to either centre line of the transformer.

Unless elsewhere specified the transformer may have either flat or skid bases, but unless
specifically approved by the Engineer, detachable underbases must not be used.

All joints other than those which may have to be broken, shall be welded.

The tank and cover shall be designed in such a manner as to leave no external pockets in
which water can lodge, no internal pockets in which oil can remain when draining the tank or in
which air can be trapped when filling the tank, and to provide easy access to all external
surfaces for painting.

Where built-on radiators are used, each radiator bank shall be connected to the main tank
through flanged valves mounted on the tank at top and bottom and each bank shall be fitted
with drain valve and air release plug.

Where cooling tubes are used, each tube shall be of heavy gauge steel welded into the tank
sides, top and bottom.

Where separate coolers are used drilled flange facings shall be provided at both ends of the
tank so that the cooler can be mounted at either end. Valves shall be provided on the tank at
each point of connection to the cooler, and between the pump and bottom header of the cooler
to facilitate the removal of the pump. Gasketted blanking plates shall be provided for the
alternative oil connections to the tank. The alternative oil inlet to the tank shall be complete
with shut-off valve and gasketted blanking plates to facilitate site handling.

Each tank cover shall be of adequate strength, must not distort when lifted and shall be
provided with suitable flanges having sufficient and properly spaced bolts. Inspection openings
shall be provided to give access to and removal of the internal connections of bushings, current
transformers, winding connections and earthing links. Each opening shall be correctly located
and must be of ample size for the purpose for which it is intended. Each inspection opening
cover shall be provided with lifting handles and its weight shall not exceed 25 kg.

It must be possible to remove any bushing without removing the tank cover.

Pockets shall be provided for a stem type thermometer and for the bulbs of temperature
indicators where specified. These pockets shall be located in the position of maximum oil
temperature and it must be possible to remove any bulb without lowering the oil level in the
tank. Captive screwed caps shall be provided to prevent the ingress of water to the
thermometer pockets when they are not in use.
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Where called for in the Schedule of Requirements, accommodation shall be provided for
outdoor weatherproof neutral current transformers.

4.3.2      Conservator Tanks, Breathers and Air Dryers

The transformer shall be provided with an overhead conservator tank formed of substantial
steel plates and arranged above the highest point of the oil circulating system. Connections
into the main tank shall be at the highest point to prevent the trapping of air or gas under the
main tank cover.

The location of the conservator tank shall be so arranged that it does not obstruct the passage
of high voltage conductors above the transformer. The pipework between the conservator and
the transformer shall comply with the requirements of Section 3 and a valve shall be provided
at the conservator to cut off the oil supply to the transformer.

The capacity of the conservator tank shall be adequate for the expansion and contraction of oil
in the whole system under the specified operating conditions. The conservator tank shall also
be provided with the following:

(i)         A removable end for cleaning purposes.

(ii)        A filling orifice with cap.

(iii)       A sump formed by projecting the feed pipe a minimum of 75mm above the bottom
            inside surface of the conservator.
(iv)        A drain valve with captive cap arranged to drain the conservator including the sump.

(v)         An isolating valve arranged on the conservator side of the oil and gas actuated relay.

(vi)        An oil level indicator, magnetic type, with indicating levels corresponding to top oil
            temperature of 5oC, plus 30oC and plus 60oC and mounted so that it is readable by a
            person standing on the ground within 600mm of the end of the conservator. To be
            supplied with low oil level alarm contacts.
(vii)       The conservator shall be fitted with an oil seal type silica gel breather. This shall be a
            type which permits the silica gel crystals to be removed for drying. Due to the climatic
            conditions at site, this breather shall be larger than would be fitted for use in a
            temperate climate. All breathers shall be mounted at a height of approximately
            1400mm above ground level.

4.3.3      Valves and Location

The transformer shall be fitted with the following valves as a minimum requirement.

Main Tank

        A. One 50mm bore filter valve located near to the top of the tank.

        B. One 50mm bore filter valve located near to the bottom of the tank and diagonally
           opposite to the filter valve required against (A). Where design permits, this valve may
           be combined with item (C).
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   C. One 50mm drain valve with such arrangements as may be necessary inside the tank to
      ensure that the tank can be completely drained of oil as far as practicable. This valve
      shall also be provided with an approved oil sampling device 15mm diameter.


   D. One valve between the conservator and gas actuated relay for the main tank and,
      where appropriate, for the tap change diverter switch tank.

   E. One drain valve for oil conservator tank so arranged that the tank can be completely
      drained of all oil.

Tap Changer Selector Switch:

   F. One 50mm filter and one 50mm drain valve where selector switches are contained in a
      separate tank.

Diverter Switch:

   G. One 50mm drain valve to be fitted to each tank. An approved oil sampling device shall
      also be provided.

Blank flanges, plates or captive screw caps shall be fitted to all valves and pipe ends not
normally connected in service.

The omission of any, or the provision of alternative arrangements to the above requirements,
will not be accepted unless approved in writing by the Engineer before manufacture.

4.3.4   Joints and Gaskets

All joint faces shall be arranged to prevent the ingress of water or leakage of oil with a
minimum of gasket surface exposed to the action of oil or air.

Oil resisting synthetic rubber gaskets are not permissible except where the synthetic rubber is
used as a bonding medium for cork or similar material or where metal inserts are provided to
limit compression.

Gaskets, having a minimum thickness of 5mm, shall be as thin as is possible consistent with
the provision of a good seal except that where jointing faces are precision machined thinner
gaskets may be used and full details of all gasket sealing arrangements shall be shown on the
Plant drawings submitted for approval.

One set of gaskets should be supplied separately so that new gaskets are available for use
during the assembly of any part of the transformer which are despatched separately (e.g.
radiators, conservators, valves etc.).
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4.3.5    Pressure Relief Device

An approved pressure relief device of sufficient size for the rapid release of any pressure that
may be generated in the tank and designed to operate at a static pressure lower than the
hydraulic test pressure called for in the Schedule of Works Tests, shall be provided.

An equaliser pipe connection shall be provided between the pressure relief device and the
conservator.The relief device is to be mounted on the tank cover or sides and is to be provided
with a skirt to project at least 25mm into the tank to prevent gas accumulation.

In the event that the device is a spring operated valve type, it shall be provided with one set of
normally open signalling contacts.

4.3.6    Earthing Terminals

Four steel flag terminals having two 14mm diameter holes on 55mm centres shall be located
one on each side and near to the bottom of the transformer to facilitate connection to the local
earthing system. Their location should be indicated on the drawings.

4.3.7    Rating, Diagram and Valve Plates

The following plates, or an approved combined plate, shall be fixed to the transformer tank at
an average height of 1500mm above the ground level:

      A. A rating plate bearing the data specified in IEC.76, Part 1. This plate shall also include
         a space for the Purchaser's serial number and in addition include the short circuit
         current rating and time factor for each winding

      B. A diagram plate showing in an approved manner, the internal connections and the
         voltage vector relationship of the several windings, in accordance with IEC.76, Part 1,
         with the transformer voltage ratio for each tap and, in addition, a plan view of the
         transformer giving the correct physical relationship of the terminals.

      C. A plate showing the location and function of all valves and air release cocks or plugs.
         This plate shall also if necessary warn operators to refer to the Maintenance
         Instructions before applying vacuum. The mass of oil shall be stated in litres and kg

Plates are to be of stainless steel or other approved material capable of withstanding the
rigours of continuous outdoor service at site.


4.4.1    Cooling Plant General

Radiators and coolers, where required, shall be designed so that all painted surfaces can be
thoroughly cleaned and easily painted in situ with brush or spray gun. The design shall also
avoid pockets in which water can collect and shall be capable of withstanding the pressure
tests specified in the Schedule of Works Tests for the transformer main tank.

The clearance between any oil or other pipework and live parts shall be not less than the
minimum clearances stated in the Schedule of Requirements.

The cooling of the transformer shall be such that failure of any one part of the cooling plant will
not result in the loss of more than 50 per cent of the total forced cooling capacity.
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4.4.2   Radiators Connected Directly to Tank

Radiators connected directly to the tank shall be detachable and shall be provided with
machined or ground flanged inlet and outlet branches. Plugs shall be fitted at the top of each
radiator for air release and at the bottom for draining.

A valve shall be provided on the tank at each point of connection to the tank.

4.4.3   Cooler banks

Each cooler bank shall be provided with:

   A. A valve at each point of connection to the transformer tank.

   B. A valve at each point of connection of radiators.

   C. Loose blanking plates to permit the blanking off of the main oil connections.

   D. A 50mm filter valve at the top of each cooler bank.

   E. A 50mm drain valve at the lowest point of each interconnecting oil pipe.

   F. A thermometer pocket, fitted with captive screw cap, in the inlet and in the outlet oil

   G. Air release and drain plugs on each radiator.

The omission of any, or the provision of alternative arrangements to the above requirements
will not be accepted unless approved in writing by the Engineer before manufacture.

4.4.4   Forced Cooling

The type of forced cooling shall be as stated in the Schedule of Particulars and Guarantees.

4.4.5   Oil Pipes and Flanges

All oil piping necessary for the connecting of the transformer to the cooler banks and oil
pumps, etc., shall be supplied under this Contract.

The oil piping shall be of approved material with machined flanged joints.

Copper pipework is to comply with BS.61.

Dimensions of steel pipes shall be in accordance with BS.3600 and the drilling of all pipe
flanges shall comply with BS.4504.

An approved expansion piece having anti-vibration characteristics shall be provided in each oil
pipe connection between the transformer and each oil cooler bank.

It shall be possible to drain any section of pipework independently of the rest and drain valves
or plugs shall be provided as necessary to meet this requirement.
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4.4.6   Air Blowers

Air blowers for forced air cooling shall be of approved make and design and be suitable for
continuous operation out-doors. They shall also be capable of withstanding the stresses
imposed when brought up to speed by the direct application of full line voltage to the motor.

To reduce noise to the practical minimum, motors shall be mounted independently from the
coolers or, alternatively, an approved form of anti-vibration mounting shall be provided.

It shall be possible to remove the blower complete with motor without disturbing or dismantling
the cooler structure framework.

Blades shall be of galvanised steel unless otherwise approved.

Blower casings shall be made of galvanised steel of thickness not less than 2.6mm (14SWG)
and shall be suitably stiffened by angles or tees.

Galvanised wire with mesh not exceeding 12.5mm guards shall be provided to prevent
accidental contact with the blades. Guards shall also be provided over all moving parts.
Guards shall be designed such that blades and other moving parts can not be touched by test
fingers to IEC.599 (BS 4590).

4.4.7   Cooler Control

Where multiple fan cooling using small single-phase motors is employed, the motors in each
cooling bank shall be grouped so as to form a balanced three-phased load.

The supply to the cooling fans shall be controlled by means of a suitably rated isolating switch
capable of being locked in the open position. The rating of the cooling control equipment shall
be based on a symmetrical fault level of at least 15,000A. A phase failure relay is to be
provided in the main cooler supply circuit.

Each motor or group of motors shall be provided with a three pole electrically operated
contactor and with control gear of approved design for starting and stopping manually. Auxiliary
contacts on each contactor shall provide an alarm to the remote control panel when any of
these contactors is open.

Where forced cooling is used on transformers, provision shall be included under this Contract
for automatic starting and stopping from the contacts on the winding temperature indicating
device. The control equipment shall be provided with a short time delay device to prevent the
starting of more than one group of fans in case of multiple fan cooling, at a time.

Each motor shall be protected by a suitable circuit breaker with thermal and short circuit
protection. Each motor circuit breaker shall have an auxiliary contact to provide an alarm to the
remote control panel in the event of the circuit breaker being open.

The control arrangements are to be designed to prevent the starting of motors totalling more
than 15KW simultaneously either manually or automatically.

All contacts and other parts which may require periodic renewal, adjustment or inspection shall
be readily accessible.
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All wiring for the control gear accommodated in the marshalling kiosk together with all
necessary cable boxes and terminations and all wiring between the marshalling kiosk and the
motors shall be included in the Contract.


4.5.1    General

Where called for in the Schedule of Requirements, transformers shall be provided with voltage
control equipment of the tap changing type for varying the effective transformation ratio.

Winding taps as called for in the Schedule of Requirements shall be provided on the high
voltage winding.

All terminals shall be clearly and permanently marked with numbers corresponding to the
cables connected thereto.

Tap positions shall be numbered consecutively ranging from one upwards. The lowest number
shall represent the tapping position corresponding to the maximum number of high voltage
winding turns.

4.5.2    On-Load Tap Changers

i)       General:

On-load tap changers shall comply with IEC.214 and BS.4571 and shall be suitable for power
flow in both directions. Only designs which have been type tested in accordance with these
standards will be accepted. Tapchangers shall be manufactured by any one of the following
approved manufactorers:

(a)     Maschinenfabrik Reinhausen - Germany

(b)     ABB Components - Sweeden

Current making and breaking switches associated with the tap selectors or otherwise where
combined with tap selectors shall be contained in a tank in which the head of oil is maintained
by means, completely independent of that on the transformer itself. The head of oil in this tank
shall be maintained either by a separate compartment of the main conservator or by a
separately mounted tank. An oil surge detector relay, an oil level indicator and a dehydrating
breather shall be provided. These requirements shall apply also for designs in which tap
selection and current making and breaking are accomplished by the same contacts within a
tank separate from the transformer.

The switches and the oil of compartments containing such switches used for making and
breaking current shall be capable, without maintenance, of performing 20,000 on-load tap
change operations or two years service, whichever is the lower.

Contacts used for making and breaking current shall be capable of performing at least 100,000
on-load tap change operations under maximum rated current conditions without replacement.

Transition resistors for on-load tap change equipment shall be mounted in the compartment
containing contacts used for making and breaking current and their measured values shall be
inscribed on the rating plate.
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Details of maintaining oil separation, oil levels, detection of oil surges and provision of alarm or
trip contacts will be dependent on the design of tap-changer and be to the approval of the

ii)       Mechanisms:

The tap change equipment shall be suitable for operation from a single phase 230V or three
phase 400V 50 Hz supply. Means shall be provided adjacent to the tap-change motor for
isolating the motor and the control gear from supply.

The tap change mechanisms shall be designed such that when a tap change has been
initiated, it will be completed independently of the operation of the control relays and switches.
If a failure of the auxiliary supply during tap change or any other contingency would result in
that movement not being completed an approved means shall be provided to safeguard the
transformer and its auxiliary equipment.

Limit switches shall be provided to prevent over-running of the tap changing mechanism.
These shall be directly connected in the operating motor circuit. In addition, mechanical stops
shall be fitted to prevent over-running of the mechanism under any conditions. For on-load tap
change equipment these stops shall withstand the full torque of the driving mechanism without
damage to the tap change equipment.

Thermal devices or other approved means shall be provided to protect the motor and control

A permanently legible lubrication chart shall be provided and fitted inside the tap change
mechanism box.

Switches, contacts and the driving mechanism shall be mounted in suitable compartments
placed in accessible positions on the transformer. Any enclosed compartment not oil-filled
shall be adequately ventilated and provided with low temperature heaters. All contactors, relay
coils and other parts shall be suitably protected against corrosion or deterioration due to

iii)      Local and Remote Control:

Equipment for local manual and electrical operation shall be provided in an outdoor cubicle.
Electrical remote control equipment shall also be supplied as specified in the Schedule of

The mounting of driving mechanisms shall minimise projection from the transformer and shall
be arranged such that the detachable manual operating handle in the driving mechanism is
approximately 1.4 metres above ground level.

Storage for the handle shall be provided within the casing of the tap changer driving

The following operating conditions are to apply to the on-load tap selector controls:

       A. It must not be possible to operate the electrical drive when the manual operating gear is
          in use.

       B. It must not be possible for two electric control points to be in operation at the same
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       C. Operation from the local or remote control switch shall cause one tap movement only
          unless the control switch is returned to the off position between successive operations.

       D. It must not be possible for any tranformers operating in parallel with one or more
          transformers in a group to be more than one tap out of step with the other transformers
          in the group.

       E. All electrical control switches and local manual operating gear shall be clearly labelled
          to indicate the direction of tap changing i.e. raise and lower tap number.

(iv)      Indications:

Apparatus of the latest technology and of an approved type shall be provided on each

       A. To give indication mechanically at the transformer and electrically at the remote control
          point of the number of the tapping in use. This indication shall not be capable of being

       B. To give electrical indication, separate from that specified above, of tap position at the
          remote supervisory point.

       C. To give indication at the remote control point that a tap change is in progress, this
          indication to continue until the tap change is completed.

       D. To give indication at the remote control point and at the supervisory control point when
          the units of a group of transformers operating in parallel are operating at more than one
          tap apart.

       E. To indicate at the tap change mechanism the number of operations completed by the

       F. To indicate at the tap change mechanism the maximum and minimum position to which
          the mechanism has moved. These indications to be resettable.

4.5.3     Automatic Voltage Control

Automatic control where specified shall be suitable for the control of transformers in parallel up
to three transformers in the future.

In addition to the methods of control covered by Clause 4.5.2, the following methods shall also
be provided.

       A. Automatic Independent: It shall be possible to select automatic independent control for
          each transformer irrespective of the method of control selected for any other of the
          associated transformers.

       B. Automatic Parallel: It shall be possible using the circulating current method.

4.5.4     Voltage Regulating Relays

Automatic voltage control shall be initiated by a voltage regulating relay of the latest technology
available for flush mounting, supplied by any one of the following manufacturers:-
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(a)    Maschninfabrik Reinhausen - Germany

(b)    ABB - Relays and Network Control - Finland

The reference voltage to the relay shall be obtained from the LV side of a voltage transformer
of ratio 66000/110, having Class 1 accuracy to BS3941. The relay voltage reference balance
point shall be adjustable.

The reference current to the relay shall be obtained from the secondary of a current
transformer of ratio 600/1A.

The relay bandwidth shall preferably be adjustable to any value between 1.5 times and 2.5
times the transformer tap step percentage, the nominal setting being twice the transformer tap
step percentage.

The relay shall be insensitive to frequency variation between the limits of 47Hz and 51Hz. The
relay shall be complete with a time delay element adjustable between 10 and 120 seconds.
The relay shall also incorporate an under voltage blocking facility which renders the control
inoperative if the reference voltage falls below 80% of the nominal value with automatic
restoration of control when the reference voltage rises to 85% of nominal value.

The LV voltage transformer supply to the voltage regulating relay shall be monitored for partial
or complete failure. The specified indicating lamp and alarm will be inoperative when:

(i)    the circuit-breaker controlling the 66kV side of the transformer is open and

(ii)   when the tap changer is on manual control.

The relay shall have the following characteristics:

1. Parallel control of 3 Transformers

2. Control using circulating current method

3. Control of motor drive unit using the step-by-step method

4. Adjustment of all configurations for measuring transformers

5. Parameter setting via PC

6. Remote/supervisory control

7. Raise/lower pushbuttons

8. Auto/manual pushbuttons

9. Voltage reference adjuster

10. Voltage indication

11. Tap Position indication
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4.5.5     Remote Control Panels

Where remote control panels are specified in the Schedule of Requirements, floor mounting
sheet steel cubicles of approved type, layout and colour shall be provided for each transformer.
Each shall form a complete enclosure with lockable rear doors and shall be fitted with interior
lamp, door switch, heaters, cable gland plates for bottom entry of cables and all other
equipment to provide the features specified, the standard requirements (which may be varied
to suit manufacturer's design) being as follows:


Automatic voltage control.

Alarm Relay: A multi-element alarm flag relay is to be provided to indicate the following:

1. Buchholz Gas
2. Winding Temperature - stage 1
3. Low oil level
4. Marshalling Kiosk AC Fail.

Trip Relay: A multi-element trip flag relay is to be provided for the following:

1. Buchholz Oil surge
2. OLTC oil surge
3. Winding temperature - stage 2

4. Pressure Relief
These alarm and trip relays are required to be latched flag relays with four hand-reset change
over contacts per element. The contacts shall be voltage free for operating the transformer
main trip relay supplied under a separate contract.

Indications and Alarms

Air forced cooling equipment running - white

Air forced cooling failure - amber

VT Fail alarm - amber

Supply voltage failure on OLTC - amber lamp

Remote control schemes shall be entirely suitable for operation with the distance between the
transformer and remote control panel as shown on drawings or stated in Schedule B.


4.6.1     Requirements

Transformer tap change control may be effected from the System Control Centre. All
necessary connections, indicating auxiliary switches, relays and changeover switches to meet
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supervisory control requirements shall be provided and connected under this Contract to
terminal blocks at the transformer marshalling kiosk or cubicle or at the remote control panel,
as appropriate. Each individual command or signal must be connected to a pair of terminals.

The following supervisory facilities are required:

4.6.2     Controls:

I.        Switching of tap changer control between Manual/Auto.

II.       Tap change raise/lower.

III.      Three stage load shedding through preset voltage reference.

Proposals for tap changer supervisory control and indication from system control centre must
be agreed with the Engineer before finalisation.

4.6.3     Indications and Alarms:

      Winding Temperature - Stage 1

      Buchholz Gas

      Low Oil Level

      11kV VT fail alarm

      Supply voltage fail on OLTC

      Tap changer motor protection operated

      Sustained voltage deviation

      Tap change incomplete

      Tap change control "on supervisory" indication

      Tap change control "on remote" (i.e. at substation) indication

      Auto/Manual control indication

      Transformer cooling fault

      Tap position indication


          Bushing Insulators and Terminals

4.7.1     General:

Unless otherwise stated in the Schedule of Requirements, transformers are to be provided with
outdoor type bushing insulators for phase and neutral terminals.

The conductor used must be to the requirements of IEC 137 using Copper based solid rod or
stranded draw-lead fitted to a suitable outer terminal.
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All bushings shall be designed and tested in accordance with IEC.137 and the minimum
creepage distance for outdoor bushings shall be as specified in the Schedules.

Bushings for 66 kV and above shall be provided with adjustable arcing horns.

Bushings shall be of sealed construction suitable for service under the very humid conditions at
site and, in addition, to the very rapid cooling of equipment exposed to direct sunlight when this
is followed by sudden heavy rainstorms.

The insulation should be free at all times of partial discharge at all voltage levels within the
working range and shall be tested for voids and partial discharges during manufacture.

Typical sections of bushing insulators showing the internal construction, method of securing
the top cap and methods of sealing shall be included in the Tender.

On all condenser bushings a tapping shall be brought out to a separate terminal for testing
purposes on site. Space on the bushing name plates shall be provided for stamping values of
initial field dissipation factor (tan DELTA) tests.

Special precautions shall be taken to exclude moisture from paper insulation during
manufacture, assembly, transport and erection.

4.7.2   Porcelain:

Hollow porcelain shall meet the test requirements of BS.4963 (IEC 233) and shall be sound,
free from defects and thoroughly vitrified. Designs based on jointed porcelains will not be
acceptable. The glaze must not be depended upon for insulation.

The glaze shall be smooth, hard, of a uniform shade of brown and shall cover completely all
exposed parts of the insulator. Outdoor insulators and fittings shall be unaffected by
atmospheric conditions producing weathering, acids, alkalis, dust and rapid changes in
temperature that may be experienced under working conditions.

The porcelain must not engage directly with hard metal and, where necessary, gaskets shall be
interposed between the porcelain and the fittings. All porcelain clamping surfaces in contact
with gaskets shall be accurately ground and free from glaze.

All fixing material used shall be of suitable quality and properly applied and must not enter into
chemical action with the metal parts or cause fracture by expansion in service. Cement
thicknesses are to be as small and even as possible and proper care is to be taken to centre
and locate the individual parts correctly during cementing.

All porcelain insulators shall be designed to facilitate cleaning.

4.7.3   Marking:

Each porcelain insulator shall be marked with the manufacturer's name or identification mark,
year of manufacture serial number, electrical and mechanical characteristics in accordance
with IEC.137. These marks shall be clearly legible and visible after assembly of fittings and not
impressed but shall be imprinted before firing.

When a batch of insulators bearing a certain identification mark has been rejected, no further
insulators bearing this mark shall be submitted and the Contractor shall satisfy the Engineer
that adequate steps will be taken to mark or segregate the insulators constituting the rejected
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batch in such a way that there can be no possibility of the insulators being re-submitted for the
test or supplied for the use of the Purchaser.

4.7.4    Mounting of Bushings:

Bushing insulators shall be mounted on the tank in a manner such that the external
connections can be taken away clear of all obstacles. Neutral bushings shall be mounted in a
position from which a connection can be taken to a neutral current transformer mounted on a
bracket secured to the transformer tank.

The clearance from phase to earth must not be less than those stated in the Schedule of

The line current transformers, where required, will be provided under this Contract and the
bushings are to be so arranged that these can be removed without disturbing the current
transformers, secondary terminals and connections or pipework.

A flexible pull-through lead suitably sweated to the end of the winding copper shall be provided
for the 66kV and higher voltage bushings and is to be continuous to the connector which is
housed in the helmet of the bushings.

When bushings with an under-oil end of a re-entrant type are used the associated flexible
pull-through lead is to be fitted with a suitably designed gas bubble deflector.

The bushing flanges must not be of re-entrant shape which may trap air.

The quality of flange surfaces shall be N7.

Clamps and fittings made of steel or malleable iron shall be galvanised and all bolt threads are
to be greased before erection.


4.8.1    Cable Boxes and Sealing End Chambers

Where 132kV, 66kV and 11kV cables terminate on transformers, there shall be provided cable

Means shall be provided for easy disconnection of the cables from the transformer bushings
for testing purposes.

4.8.2    Testing

The cable box and disconnecting or sealing end chamber shall be capable of withstanding for
fifteen minutes both at the time of the first test on the cables and at any subsequent time as
may be required, between phases and to earth a test voltage equal to:

              2E kV dc or an ac test equal to 1.3E kV.

              Where E = r.m.s., nominal system voltage in kV between phases.

During these tests, the links in the disconnecting or sealing end chamber will be withdrawn and
the transformer windings with connectors thereto will be earthed.
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4.8.3    Supply of Cables

Auxiliary power and multicore control cables between the integral parts of the transformer, its
marshalling kiosk or tank mounted cubicle and ancillary equipment shall be installed, glanded
and have individual cores identified and terminated under this Contract.

Cables from each transformer to its associated remote control and protective equipment, to
auxiliary supply switchboards and interconnections with other transformers will be supplied,
glanded and have individual cores identified and terminated under another contract.

4.8.4    Cable Support Brackets

Where 132kV, 66kV and 11kV cable boxes are fitted the transformers shall be supplied with
suitable cable support brackets for supporting adequately the cables both under normal
operating conditions and under upnormal conditions such as during short circuit.


4.9.1    Temperature Indicating Devices and Alarms

The transformer shall be provided with two approved devices for indicating the hottest spot HV
and LV temperatures. The devices shall have a dial type indicator, and in addition, a pointer to
register the highest temperature reached. Each winding temperature device shall have three
separate contacts fitted, one of which shall be used to control the cooling plant motors, one to
give an alarm and one to trip the associated circuit-breakers. The dial of the temperature
indicators shall have a scale ranging from 30oC to 150oC preferably uniformly divided.

To simulate indication of the hottest spot temperature of the windings the device shall comprise
a current transformer associated with one phase only and a heating device designed to
operate continuously at 130 percent of transformer CMR current and for thirty minutes at 150%
of CMR current, associated with a sensing bulb installed in an oil tight pocket in the
transformer top oil. One CT shall be installed in the HV winding termination and the second in
the LV winding termination.

The winding temperature indicators shall be housed in the marshalling cubicle. The tripping
contacts of the winding temperature indicators shall be adjustable to close between 80oC and
150oC and to re-open when the temperature has fallen by not more than 10oC.

The alarm contacts and the contacts used to control the cooling plant motors and initiate
automatic start-up of the reserve cooler on the above devices shall be adjustable to close
between 50oC and 100oC and to re-open when the temperature has fallen by a desired amount
           o           o
between 15 C and 30 C.

All contacts shall be adjustable to a scale and must be accessible on the removal of the cover.
Alarm and trip circuit contacts shall be suitable for making or breaking 150VA between the
limits of 30V and 250V AC or DC and of making 500VA between the limits of 110V and 250V
DC. Cooler motor control contacts shall be suitable for operating the cooler contactors direct,
or if necessary, through an interposing relay.

The temperature indicators in the marshalling kiosk shall be so designed that it is possible to
move the pointers by hand for the purpose of checking the operation of the contacts and
associated equipment.
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The working parts of the instrument shall be made visible by the provision of cut-away dials
and glass-fronted covers and all setting and error adjustment devices shall be easily

Connections shall be brought from the device to terminal boards placed inside the marshalling

Isolating and test links and a 63 mm moving iron ammeter shall be provided in the marshalling
kiosk for each winding temperature indicator for:

   A. Checking the output of the current transformer.

   B. Testing the current transformer and thermal image characteristics.

   C. Disconnecting the bulb heaters from the current transformer secondary circuit to enable
      the instrument to be used as an oil temperature indicator. Links shall be provided as
      shown on the drawing enclosed with this specification.

The calibration of the indicator shall be related to the winding having the maximum temperature
rise. If the values on the winding temperature indicator vary by more than plus or minus 3oC
from the values derived during the temperature rise tests specified in the Schedule of
Particulars, adjustment shall be made to the equipment to achieve these limits.

4.9.2   Gas and Oil Actuated Relays

The transformer shall be fitted with gas and oil-actuated relay equipment having alarm contacts
which close on collection of gas or low oil level, and tripping contacts which close following oil
surge conditions.

Each gas and oil-actuated relay shall be provided with a test cock to take a flexible pipe
connection for checking the operation of the relay.

Each relay shall be fitted with a calibrated glass window for indication of gas volume.

A machined surface shall be provided on the top of each relay to facilitate the settings of the
relays and to check the mounting angle in the expansion pipe and the cross level of the relay.

A straight run of pipe shall be provided for a length of five times the internal diameter of the
pipe on the tank side of the gas and oil actuated relay and three times the internal diameter of
the pipe on the conservator side of the gas and oil-actuated relay.

To allow gas to be collected at ground level, a small bore pipe shall be connected to the gas
release cock of the gas and oil-actuated relay and brought down to a point approximately
1400mm above ground level, where it shall be terminated by a cock which shall have provision
for locking to prevent unauthorised operation.

The design of the relay mounting arrangements, the associated pipework and the cooling plant
shall be such that maloperation of the relays will not take place under normal service
conditions, including starting or stopping of oil circulating pumps whether by manual or
automatic control under all operating temperatures.

The pipework shall be so arranged that all gas arising from the transformer will pass into the
gas and oil-actuated relay. The oil circuit through the relay must not form a delivery path in
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parallel with any circulating oil pipe, nor is it to be teed into or connected through the pressure
relief vent. Sharp bends in the pipework shall be avoided.

The transformer shall be provided with two gas and oil-actuated relays piped separately to the
conservators for the transformer main tank and for the tap changer.

4.9.3   Marshalling Cubicles

The transformer ancillary apparatus shall be mounted in an approved heated and ventilated
cubicle, attached to the transformer.

The cubicle shall preferably be divided into four separate compartments for the
accommodation of the following equipment.

    A. Temperature indicators, cooler control "Auto-Hand" selector switch and test links and
       ammeter for the winding temperature indicator circuits.

    B. Control and protection equipment for the tap change gear including an isolating switch
       in the incoming circuit capable of carrying and breaking the full load current of the
       motor and of being locked in the open position.

    C. Control and protection equipment for the cooling plant including an isolating switch in
       the incoming circuit capable of carrying and breaking the full load current of all cooling
       plant motors and of being locked in the open position.

        The control facilities shall include a cooler selector switch which can be padlocked in
        either position to select either cooler for remote control. Local control of the selected
        cooler shall be provided.

    D. Terminal boards and gland plates including glands where specified for incoming and
       outgoing cables. Provision shall also be made for termination of secondary wiring of
       current transformers where specified.

All doors shall be fastened by integral handles with provision for locking each door.

The Temperature indicators shall be so mounted that the dials are not more than 1700mm
from ground level and the door(s) of the compartment shall be provided with glazed windows of
adequate size.

Facilities shall be provided to permit the temperature indicators with capillary tubing and bulbs
to be removed from the cubicle. Mechanical protection shall be provided and sharp bends
avoided where the capillary tubes enter the cubicle.

To prevent internal condensation an approved type of metal clad heater shall be provided,
controlled by a switch and a 5A fuse inside the cubicle to be supplied from a separate
substation "heating" supply circuit.

All internal wiring shall be so placed as not to obstruct access.

Labels in addition to those specified elsewhere shall be provided on the outside of the kiosk to
identify the compartments.

All three-phase relays, contactors, isolating switches and thermal devices shall be marked with
appropriate phase colour. Apparatus in which the phase elements are mounted horizontally
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shall be coloured red, yellow, blue from left to right when viewed from the front of the panel,
and when mounted vertically they shall be coloured red, yellow, blue from top and bottom.

The kiosk shall be fitted with the following interlocked switch sockets, mounted externally to
provide auxiliary supply points:

   1. Weatherproof 15A 3 pin switched socket, Walsall type SP51/55 list No. 2193 for 240V
      AC complete with plug. The switched socket shall be connected to the cubicle heater
      supply circuit through a 15 ampere fuse or MCB in the live lead.

All supply circuits in the marshalling cubicles shall be monitored to alarm to the remote control
panel in case the supply to the circuit is OFF or tripped.


The transformer shall be dried out by an approved method at the manufacturer's works and so
arranged that they might be put into service without further drying out on site. The Contractor
shall submit to the Engineer for his approval details of the method which they recommend
should be adopted for drying out the transformers on site should it prove necessary to do so.

Clear instructions shall be included in the Maintenance Instructions regarding any special
precautionary measures (e.g., strutting of tap changer barriers or tank cover) which must be
taken before the specified vacuum treatment can be carried out. Any special equipment
necessary to enable the transformer to withstand the treatment shall be provided. The
maximum vacuum which the complete transformer, filled with oil, can safely withstand without
any special precautionary measures being taken is also to be stated in the Maintenance

4.11 OIL

The Contractor shall supply the first filling of transformer oil which shall be in accordance with
BS148 or to IEC 296. Details of the oil to be supplied should be given in the Schedule of

Where the transport weight of transformers does not exceed 50000 kg these can be shipped
partly oil filled with sufficient oil to cover the windings and the insulation.

The oil shall be under controlled nitrogen pressure of about 0.3 atmospheres.

Alternatively the transformer can be shipped without oil with the tanks filled with nitrogen under
pressure of about 30.4 kPa. The Tenderers shall submit with their offer details on how they
propose to ship the transformers for approval by the Engineer. The Tenderers must also
supply full details on filling up the transformer with oil after delivery.


4.12.1 General

Where specified in the Schedules of Requirements transducers shall be supplied for the
purpose of generating dc analogue signals for use by the SCADA system and shall comply
with IEC 688-1 and the requirements stated below.

All transducers shall have an accuracy class of 0.5 unless stated otherwise.
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The transducer output shall be proof against short circuit and open circuit conditions and shall
be rated to drive a load of 1000 Ohms connected to the SCADA interface terminals (any other
loads connected to the transducer and any cable burdens within the scope of the switchgear
supply shall be allowed for additionally to the SCADA load). User adjustment of the transducer
output shall be provided.

Where transducers require an auxiliary power supply, this shall be derived from the substation
dc supply.

The transducer response time shall not exceed 0.5 seconds.

Ripple current in the transducer output shall not exceed 0.5% r.m.s.

4.12.2 Transformer Tap Position supervisory indication

The Transformer Tap Position supervisory indication shall be provided by the use of suitable
BCD or Gray Code units whose input shall be connected to Volt free transfer tap position
contacts. The BCD or Gray code units shall be based on diode matrix technology suitable for
nominal operating voltage 50V DC. Special plug in wire termination blocks shall be provided
for easy connection/disconnection of the unit.



The whole of the Plant covered by this Contract will be subject to inspection and test by the
Engineer during manufacture and on completion. The approval of the Engineer or the passing
of any such inspection or test will not, however, prejudice the right of the Purchaser to reject
the Plant if it does not comply with the Specification when erected to give complete satisfaction
in service. The costs of all tests and inspection shall be borne by the Contractor and shall be
deemed to be included in the Contract Price.

Before any Plant is packed or despatched from the Main or Sub-Contractor's works, all tests
called for shall have been successfully carried out in the presence of the Engineer.

Adequate notice shall be given when the Plant is ready for inspection or test and every facility
shall be provided by the Contractor and his Sub-Contractors to enable the Engineer to carry
out the necessary inspection and tests.


Within two months of acceptance of the Tender the Contractor shall forward to the Engineer a
list of all sub-orders placed or intended. The Contractor shall submit a copy of all sub-orders
as selected by the Engineer for progress or inspection. One copy of all drawings referred to in
the sub-orders is to be submitted, unless otherwise agreed by the Engineer.

The drawings and sub-orders submitted to the Engineer shall cover all components which are
subject to electrical and mechanical pressure or stress when the Plant is in operation and also
those items which will be despatched to Site direct from the Sub-Contractor's works.

For the purpose of this Clause, interworks shall be treated as sub-orders.

Sub-orders shall include a statement advising the Sub-Contractor that the items being ordered
will be subject to inspection and test by the Engineer.
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It is important that all copies of sub-orders are clearly marked with the name of the Contractor
and the following reference:

Purchaser's Name

Contract Number.

Sub-Contractors shall comply with all the applicable requirements of this Specification and, in
particular, with this Section. Orders issued by the Sub-Contractor shall also include the Main
Contractor's name and reference on their sub-order in addition to the above-mentioned


The Contractor shall provide test pieces as required by the Engineer to enable him to
determine the quality of the material supplied under this Contract. Such test pieces shall be
prepared and supplied free of charge and any cost of the tests shall be borne by the
Contractor. If any test piece fails to comply with the requirements of the appropriate
specifications for the material in question, the Engineer may reject the whole of the material
represented by that test piece; the Contractor's designers and metallurgists will be consulted
before any material is so rejected.

In the event of the Engineer being furnished with certified particulars of tests which have been
carried out for the Contractor by the suppliers of materials, they may, at their own discretion,
dispense with the previously mentioned test entirely.


After the Contract has been awarded and the main features of the project design are known,
then an Engineer's Inspection and Testing Programme shall be established by the Contractor.

The Engineer reserves the right to call for such additional tests as may be necessary to prove
compliance with the Specification.

Unless an alternative place of testing is agreed or specified the routine tests shall be carried
out at the Manufacturer's Works.

Type tests will not be required to be repeated and the Contractor must produce certified
evidence to the satisfaction of the Engineer that the required type tests have been performed
successfully on identical equipment or equipment which is for practical test purposes similar
and produced in the factory where the equipment offered is to be manufactured. Evidence to
this effect shall be submitted at the time of tendering.

Tenders will not be considered if such evidence is not produced.

Where a type tested design is manufactured under licence in a different location evidence of
repeat type tests appropriate to the alternative manufacturing location is required.

Inspection and testing during manufacture shall be in accordance with the General Conditions
of Purchase and this section of the Specification.

Works tests shall include all routine electrical, mechanical and hydraulic tests in accordance
with the relevant Standards except where departures therefrom and modifications thereto are
embodied in this Specification. For Plant not covered by any IEC or British Standard or
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specifically mentioned in this Specification, such tests as are relevant shall be agreed with the

Should the Plant or any portion thereof fail under test to give the required performance, further
tests which are considered necessary by the Engineer shall be carried out by the Contractor
and the whole costs of the repeated tests borne by the Contractor. This applies to tests carried
out at the Sub-Contractor's works.

After satisfactory completion of the witnessed tests at the Works, the Plant shall be submitted
for the Engineer's approval during dismantling preparatory to shipping. No item of Plant is to
be despatched to Site until the Engineer has given his approval in writing.


One set of all principal test records, test certificates and performance curves shall be supplied
for all tests carried out in accordance with the provisions of this Contract. These tests records,
certificates and performance curves shall be supplied for all tests, whether or not they have
been witnessed by the Engineer. The information given in such test certificates and curves
shall be sufficient to identify the material or equipment to which the certificate refers and should
also bear the Contract reference and the Purchaser's name.

These records shall be clearly marked so that the Contract equipment items or components to
which they refer can be readily identified.


If any item fails to comply with the requirements of this Specification in any respect whatsoever
at any stage of manufacture, test, erection or on completion at Site, the Engineer may reject
the item, or defective component thereof, whichever he considers necessary, and after
adjustment or modification as directed by the Engineer, the Contractor shall submit the item for
further inspection and/or test.

In the event of a defect on any item being of such a nature that the requirements of this
Specification cannot be fulfilled by adjustment or modification, such item is to be replaced by
the Contractor, at his own expense, to the entire satisfaction of the Engineer.


5.7.1    General

A list of the tests at the manufacturer's works and at site is given below.

The following tests shall be made in order to determine compliance with the Specification.

A detailed programme for the works tests accompanied by a method statement for each test
shall be prepared by the Contractor and submitted for the Engineer's approval well in advance
of the programmed testing period. As many tests as practically possible shall be arranged
together, in agreement with the Engineer.

Not less than 30 day notice of all tests shall be given in order that the Engineer's representative
may be present if so desired.
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5.7.2   MAIN TRANSFORMER Routine Tests

I.      The transformer shall be subject to the following routine tests:

II.     Correct functioning of the tap-changer and driving mechanism.

III.    Measurement of winding resistance on all tap positions and phases.

IV.     Measurement of Voltage ratio and check of voltage vector relationship.

V.      Measurement of impedance voltage, on all tap positions.

VI.     Measurement of load loss.

VII.    Measurement of no load loss and no load current.

VIII.   Insulation resistance.

During the tests listed below the transformer shall be equipped with the bushings that will be in
permanent operation.

I.      induced overvoltage withstand

II.     short duration power frequency voltage withstand

III.    lightning impulse withstand for line terminals

IV.     lightning impulse chopped wave - 100%.

The following are noted regarding the impulse voltage withstand tests:

A.      The transformer shall have been subjected to the above routine tests prior to the
        impulse voltage withstand tests.

B.      Impulse test on regulating windings shall be carried out on the principal and on the
        extreme tap positions.

C.      The procedure shall be as required by IEC76 Part 3, Clause 13, the impulse test
        voltages being applied successively to each line terminal. Negative polarity is to be
        used throughout the tests.

        The sequence of voltage applications shall be:

        a) One reduce impulse calibration test.

        b) One 100 per cent full wave voltage application.

        c) One reduced chopped wave voltage application.

        d) Two 100 per cent chopped wave voltage applications.

        e) Two 100 per cent full wave voltage applications.
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         Oscillographic records of the applied voltage and neutral current and/or transferred
         voltage are to be taken and included in the records.

         Copies of the oscillographic records are to be made available to the Engineer at the
         time of the tests for his examination.

         External flashover of the bushings during the chopped wave tests is not permitted.

D.       At the conclusion of the impulse voltage withstand tests, the transformer shall again be
         subjected to the routine tests (VI) and (VII). Special Tests

These tests might be waived if they have been performed earlier for the same type and size of

In such a case, the relevant test reports must be submitted with the tender documents.

    Temperature Rise Test:

        The test shall be in accordance with IEC.76, Part 2. Temperature-rise tests shall be
         conducted on the tapping corresponding to the maximum losses.

    Noise Level Test:

        A noise level test to IEC.76 shall be carried out in accordance with IEC.551.

        In addition the transformer noise level shall be measured with the transformer
         energised at the maximum flux density.

    Frequency Spectrum Test:

        The purpose of this test is in order to establish the noise spectrum for noise insulation

        This test shall be carried out over a frequency band of 50 Hz to 8 kHz, at 50Hz intervals
         up to 500 Hz and 100 Hz intervals up to 8 kHz with noise level measured at each point.
         The tests shall be carried out with the transformer de-energised and also with the
         transformer energised with fans running. Measurements shall be made on both axes at
         about 3m distance from the transformer. Other details will be agreed at the time of the

    Zero Sequence Impedance:

        Measure the zero sequence impedance of star connected or zigzag connected
         windings in Accordance with clause 8.7 of IEC76.1


Each finished tap changer is to be subjected to the routine tests specified in IEC.214 but in
addition the mechanical test shall be carried out at rated voltage and no load.
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                                                                          Issue 1, dated 10.9.2002 Type Tests

Test Certificates shall be submitted at the time of Tendering confirming compliance with
IEC.214 except that evidence of the service duty type test shall be in excess of 100,000

5.7.4    MAGNETIC CIRCUIT Routine Tests

Each core completely assembled is to be tested for one minute at 2,000V AC between core
bolts, side plates, structural steelwork and core at the core and coil stage. After the
transformer is tanked and completely assembled, a further test is to be applied between the
core and the earthed structural steelwork to prove that the core is earthed through the
removable link, at one point only. Magnetisation Curves

Magnetisation (Full B/H) curves shall be supplied by the manufacturer with the test reports
based on the test values for voltages upto 110% of nominal and on calculated values for
nominal voltages above 110% upto 140%. With the magnetizing curves the following data
shall be supplied for each distinct design included in the scope of supply.

    Magnetizing reactance type (Linear/piecewise lines)

    Magnetizing reactance knee flux.

    Magnetizing linear reactance

    Magnetizing saturated reactance

    Saturation exponent (if not linear)

    Inrush peak current maximum time

    Thermal withstand ratio Ith/In

    Thermal withstand maximum time

5.7.5    CABLE BOXES Routine Tests

To meet the requirements referred to elsewhere in this Specification.


The following sample tests in accordance with IEC.233 are to be made:

a)      Temperature Cycle Test.

b)      Porosity Test.
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The complete bushings are to be tested in accordance with IEC.137. Routine Tests

I.       To include:

II.      Oil leakage test

III.     50Hz dry withstand test

IV.      Power factor/voltage test

V.       Partial discharge test on bushings of which the major insulation is either oil impregnated
         paper or resin impregnated paper. Type Tests

Test Certificates shall be submitted with Tender Documents to confirm compliance with IEC
137 in respect of:

I.      50Hz Wet withstand test

II.     Impulse voltage test

5.7.8    TANKS Routine Tests

Oil Leakage:

All tanks, conservators and oil filled compartments which are subjected in service or during
maintenance to oil pressure are to withstand without leakage, a hydraulic pressure test equal
to 69kN/m2 or the normal pressure plus 34kN/m2 whichever is the greater, for 24 hours during
which time no leakage or oil ingress into normally oil free spaces shall occur. Type Tests

Type Test Certificates shall be produced for tests carried out on similar equipment and the
following tests are included for tanks and conservators.

I.      Vacuum Test:

        The equipment is to withstand a full vacuum of 760mm of mercury when empty of oil.
        The permanent deflection of plates or stiffeners on removal of vacuum is not to exceed
        the following values:

         Length of Plate                        Permanent Deflection
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         Less than 1300mm                       3.17mm

         1300 to 2500mm                         9.5mm

         Greater than 2500mm                    12.7mm

II.     Pressure Test:

        The equipment is to withstand a pressure corresponding to 69kN/m2 or the normal
        pressure plus 34kN/m2 whichever is the greatest. The permanent deflection of plates or
        stiffeners on removal of pressure is not to exceed the value stated in respect of the
        vacuum test in the preceding paragraph.

5.7.9    COOLING PLANT - Routine Tests

a)      Coolers:

        Pressure test to be as specified in above paragraphs.

b)      Motors and Control Gear:

        To the requirements referred to elsewhere in this specification.

c)      Cooling system:

        Automatic and manual operation of the system shall be checked.

5.7.10 GAS AND OIL - ACTUATED RELAYS - Routine Tests

a)      Oil Leakage:
        When subject to an internal oil pressure of 207kN/m for fifteen minutes.

b)      Gas collection

c)      Oil Surge

d)      Performance test under service conditions

e)      Voltage:

        2kV for one minute between electrical circuits and casing.

5.7.11 GALVANIZING - Routine Tests

To the requirements of BS.443 or BS.729 whichever is applicable.


All current transformers shall be subjected to the routine tests specified in BS3938. Copies of
all test records should be submitted to the Engineer. Also one copy of each test record should
be included in the relative Operating, Maintenance and Installation Manuals.
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ting, Maintenance and Installation Manuals.

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