Document Sample
                                                     Copyright Material IEEE
                                                     Paper No. PCIC-2000-29
         James A. Oliver                                Roger Lawrence                        Basudeb Ben Banerjee
         Fellow IEEE                                    Senior Member IEEE                    Senior Member IEEE
         Jarsco Engineering Corp.                       EPRl ASDO                             EPRl
         18901 State Street                             1017 Main Campus Drive                3412 Hillview Avenue
         Corona, CA 92881                               Raleigh, NC 27606                     Palo Alto, CA 94303
         USA                                            USA -                                 USA

Abstract The concept of the power quality problem is
presented, which is the susceptibility of industrial                              II.    WHAT IS POWER QUALITY?
equipment reliability to electric power quality abnormalities.
These abnormalities are characterized. The power quality               A Power Quality problem is an occurrence manifested in a
study approach is presented. Mitigation practices are                non-standard voltage, current, or frequency deviation,
reviewed. How to include power quality tolerance                     which results in a failure or a misoperation of end-use
requirements in specifications for new process equipment             equipment. Power Quality is a reliability issue driven by
is discussed. An industry survey of PQ mitigation is                 end users. There are three concerns:
presented                                                            1) The characteristics of the utility power supply can have
                                                                           a detrimental effect on the performance of industrial
Index Terms - Power Quality, Voltage Transients,                           equipment.
Interruptions, Sags, Harmonics, PQ Mitigation, Static VAR            2) Harmonics produced by industrial equipment, such as
Compensator.                                                               rectifiers or ASDs, can have a detrimental effect on the
                                                                           reliability of the plant electrical distribution system, the
                    1.   INTRODUCTION                                      equipment it feeds, and on the utility system.
                                                                     3) The characteristics of the current and voltage
  With the intense drive for profits, industrial plants are                produced by ASDs can cause motor problems.
concerned about any kind of production shut down. At the               While Power Quality is basically voltage quality, it is not
same time, sophisticated electronics are being rapidly               strictly a voltage issue. Since the supply system has a
introduced into most production processes. These are                 finite, rather than an infinite strength, currents outside the
often in the form of such power quality-sensitive equipment          direct control of the utility can adversely affect power
as these:                                                            quality. These are harmonic load currents, lightning
1) Computers                                                         currents, and fault currents. How do we quantify voltage
2) Telecommunications                                                aberrations indicative of power quality problems?
3) Electronic Process Controls                                         One must employ an accurate voltagemeasuring device,
4) Robotics                                                          such as an oscilloscope. to identify which of the voltage
5) Adjustable Speed Drives                                           aberrations of Table 1, and discussed below, is causing the
  The reliability of this type of equipment is much more             problem.
closely tied to the quality of the power supply, as compared
to older or more traditional equipment, which might have                                              I
had relay controls or electrical contactor controls.
 For the past 15 years or so, there has been an increasing
awareness of the Power Quality problem. In 1991,                                                 Figure 1
Business Week magazine reported that spikes, sags and                                   Impulsive Transient Voltage
outages cost the nation $26 billion in downtime.
Contributing to this cost is lost time, lost produdion,                 1)     Transients - Impuisive: These are commonly
production of scrap, lost sales, delivery delays, and                known as switching surges or voltage spikes, Figure 1.
damaged production equipment. Now, with utilities facing             They can be caused by Circuit breakers out of adjustment,
competition in who supplies power, particularly to their             by capacitor switching, by lightning, or by system faults.
major industrial customers, mitigating power quality                 They are characterized by a sudden, non-power frequency
problems is foremost on the utilities' agenda.                       change, by a high amplitude, by fast rise and decay times,
  There is a need to understand the Power Quality issue.             and by high energy content.
The source of the power quality problem is not a given.
The unacceptable quality of power may be a utility
responsibility, or it may be a self-generated responsibility of
the industrial facility. With so much at stake, it behooves
both utilrty and industly to quickly identify the problem and                                      Figure 2
eliminate it.                                                                           Oscillatory Transient Voltage

 0-7803-6334-5/00/$10.00 0 2000 IEEE                                                                                        00CH37112
                                                              -281   -
    2) Transients Oscd&tory. This is a sudden, bi-
directional, non-power frequency change: a ringing, Figure
                                                                            6)      Voltage Flicker:        Flicker comes from the
                                                                        aggravating, rapid on-off sensation of incandescent and
2. For high frequency ringing, ~ 5 0 kHz of ps duration, and
                                      0                                 fluorescent lamps as perceived by the human eye. It
for 5 to 500 kt-k ringing with lo's of p duration, it is likely         results from the rapid variation in voltage, within the normal
the result of either the system response or the load                    allowable voltage range tolerance of 90 to 1lo%, Figure 6.
response to an impulsive transient. Wt a frequency of 4
                                        rh                              Flicker can result from electric arc furnaces, welders,
kHz and 0.3-50ms duration, it could have one of a number                rapidly cycling loads, or it can result from a large AS0 with
of Causes.                                                              inadequate dc link filtering on a weak distribution system.
                                                                        Wrth inadequate dc link filtering, the inverter harmonics,
                                                                        which are a function of a non-60 Hz fundamental, flow into
                                                                        the power system, causing a pulsating of the 60 Hz
                                                                            7) Voltage Regulation. Low voltage during peak load
                           Figure 3                                     periods can result from overloaded lines, improperly set
                         Voltage Sag                                                           r
                                                                        transformer taps, o maladjusted automatic voltage
                                                                        regulators. The voltage is less than the normal 90% lower
   3 Voltage Sag: This is a short-term, a few cydes
    )                                                                   limit. Symptoms are dim light bulbs, light bulbs burning out
duration, drop in voltage, Figure 3, on the order of more               too often, electric motors failing to start.
than 10% to less than 90%. Typically, it lasts from 0.5                     8) frequency fluctuations: Normally, the variation in
cycles to a minute. Voltage sags result from the voltage                frequency is not significant enough to cause any problems.
drop from starting big motors across-theline, or from a fault           Frequency tends to lag a little during the day as central
on an adjacent power line.                                              plant generators are well loaded, but at night with light load,
                                                                        the frequency leads a little, so that at the end of a 24-hour
                                                                        period, all docks are correct. Deviations in frequency can
                                                                        occur in weak electric systems, such as an island system
                                                                        with no main supporting ties to the mainland, or a an     t
                                                                        industrial plant with its own generating system. A weak
                                                                        system could develop during an area-wide system
                          Figure 4                                      disturbance that separates one part of the system from
                        Voltage Swell                                   another.

    4)    Voltage Swell: This is a short-term increase in
voltage of a few cycles duration, Figure 4. The magnitude
of the increase is more than 10% and less than 80%. A
swell can result from a single line to ground fault which                                         Figure 7
raises the voltage on the other two phases. It can also                                   Harmonic Voltage Distortion
result from dropping a large load or from energizing a
capacitor bank.                                                             9 Voltage Distortion: Voltage distortion is the degree to
                                                                        which the voltage wave shape deviates from a sine wave.
                                                                        Distortion can result from the following:
                                                                        1) Harmonics
                                                                        2) lnterharmonics
                        Figure 5                                        3) Voltage Notching
                   Momentary Interruption                               4) Noise
                                                                        5) DCOffset
    5) Intemption: Ninety percent of the faults on overhead                 10) Harmonics: Voltage distortion, Figure 7, is well-
distribution lines are of a temporary nature, Figure 5.                 understood. It is defined and thoroughly discussed in IEEE
Typically, these faults result from lightning, tree limbs or            Standard 519. Non-linear elements in power systems,
animals causing grounds or shorts. Distribution lines are               such as power electronic switches, saturated magnetic
protected by a form of circuit breaker called a 'Recloser".             components, and arc furnaces create current distortions.
Reclosers interrupt faults, then they automatically restore             Harmonic currents flowing through system impedances
the circuit, or redose, and if the fault has cleared, the               create harmonic voltages. IEEE Std. 519 suggests voltage
recloser stays dosed. If the fault still persists, the recloser         and current distortion limits at the connection point between
trips and again automatically closes back in. It usually                the industrial facility and the electric utility, e.g. the 'point of
recloses three times before locking out.                                common coupling".
                                                                          Harmonics can cause such problems as telephone
                                                                        interference, motor overheating, transformer overheating,
                                                                        capaator fuse blowing, high neutral currents, and problems
                                                                        with electronic controls. Distorted timedomain voltage and
                                                                        current wave shapes are evaluated with spectrum analyzer
                           Figure 6                                     equipment utilizing Fourier Transform algorithms to
                        Voltage Flicker                                 calculate frequency domain magnitudes and phase angles

                                                              - 282 -
of individual harmonic components. Solutions to harmonic                       fundamental 60 Hz frequency, Figure 8. They can result
problems indude the use of transformer connections,                            from ASDs with insufficient dc link filtering.           Whn
harmonic filters, optimum spacing of conductors, shielding                     inadequate dc link filtering, inverter harmonics which are
and grounding schemes.                                                         multiples of a "-t-60 Hz fundamental, pass into the power
                                                                               system, where they appear as non-multiples o the 60 Hz
Typical accepted, defined value ranges for voltage                             fundamental. This phenomenon can also occur with cydo-
aberrations are listed in TABLE 1.                                             converter type ASDs which have no dc link, and with arc
                                                                               furnaces, which develop an infinite spectrum of parasitic
                                                                                   12) Voltage Nofching: Voltage notching is a periodic
                                                                               voltage disturbance resulting from the normal operation of
                                                                               power electronic devices, such as thyristors. Notching,
    Impulsive            Spectral         Typical            Voltage           Figure 9, is not normally a problem since it is controlled by
    Transients           Content          Duration           p.u.              circuit elements assodated with the switching devices. It
     Short               5 ns rise        <50 ns                               can be a
     Medium              1 ps rise        50 n s 1 ms
     Lana                -1 ms rise       > 1 ms

I   Oscillatory
     Low Freq.
                     I4     kHz
                                      I   0.3-50ms
                                                         I   0-4
     Med. Freq.          5-500kHz         20 ps              0-8
     High Freq.          0.55 MHz         5 ms               0-4                                       Figure 8
I   Short            I                I                  I                                  Voltage Wave with Interharmonics
                     I                I   0.530Hz        I   c0.1

                                                                                                           Figure 9
                                                                                                Distorted Voltage with Notching

                                                                               significant problem on weak electric systems, where it can
                                                                               produce noise currents causing control system misopera-
                                                                               tion. Notching and ringing can cause extra zero crossings
                                                                               resulting in equipment malfunction in some equipment.

    Interruption,                         >I min             0.00
    Sustained                                                                               c
    Under                                 >1 min             0.8-0.9
    voltages                                             I
    over                              I > I min          I   1.1-1.2                                   Figure 10
                                                                                                Common Mode Noise Current
    Voltage                           I   Steady-State I 0.050.2
I Unbalance
  -. .- -. -. .- -   1                I
                                                         I                         13) Noise: Fast switching speed and high input
    DC Offset        I                I Steady-state I 0-0.01                  impedance give IGBT (Insulated Gate Bi-Polar Transistor)
    Harmonics        10-100"'         I Steady-state I 0-.20                   inverters the potential to produce stray currents resulting in
                     I harmonic       I                                        electromagnetic interference (EMI). Stray currents can
     Inter           I 0.6 kHz        I   Steady-state   I 0-.02               disrupt communications equipment, ASD control, program-
    harmonics                                                                  mable controllers, sensors, barcode scanners and position
    Notching                              Steady-state                         sensing equipment. These commommode noise currents,
    Noise                Broad            Steady-state       @.01              Figure I O , are mainly conducted currents. They are
                         band                                                  superimposed on and can overwhelm low voltage control
      Voltage            c25 Hz           Intermittent       0.01-.7           signals with these adverse effects. The magnitude of the
    Fluctuations                                                               stray currents is determined by the amount of phase-te
      Power                               <IO s                                ground stray capacitance coupling available during the
    Frequency                                                                  approximate 0.05 to 0.1 psec time period when the inverter
    Variations                                                                 voltage is transitioning to and from the dc link voltage level.

                                                                       - 283   -
             111.   THE POWER QUALITY STUDY                                conditioning equipment. Obtain a singleline diagram
                                                                           of the plant electrical system, with transformer ratings
 When there is a power quality problem, it is often'                       and impedances. Identify any power factor correction
necessary to analyze both the utility electric supply system               capacitors.
and the electric system of the industrial faality. A                       Look for loads that disrupt power quality, such as
monitoring program is set up, and at the same time, a                      A s h , arc furnaces, induction heating units, welders,
model mathematical simulation is run. The latter is done to                or power electronic rectifiers.
provide insight into the nature of the problem and to allow                ldentrfy loads that are sensitive, such as computers,
simulation of a fix. The approach is as follows:                           telecommunications systems, process oontrds,
1) Identify the PQ concerns.                                               robotics, and ASDs.
2) Collect system data for both the utility system and the                 Considerable insight into the problem can be obtained
    Industrial plant.                                                      by discussing the problem with the plant engineers.
3) Set up a monitoring program.                                            Such a discussion would indude a history of the
4) Set up a model and simulation program.                                  problem, an evaluation of wiring, cable shielding and
5) From the resutts of the monitoring and the simulation,                  grounding practices, and identication of sensitive
    develop solutions.                                                     equipment.

A.    Simulation Models                                                    Monitoring Equipment

There are several computer programs available for the                 The basic measuring tools for the power quality field test is
Power Quality study. Harmonic analysis programs can be                the power quality monitor. Other useful tools are the
used for calculating harmonics, notching and noise.                   ground resistance meter, megohmmeter, Circuit tester,
Electromagnetic transients programs (EMTP) are used for               multimeter, infrared scanner and damp-on current probes.
a variety of studies, as in Table 2 (from IEEE 1159):                 There are a variety of power quality monitors available.
                                                                      The correct monitor for the job should be selected. Some of
                            TABLE 2                                   the key functions to consider in selecting a power quallty
                     CAPABILITIES OF EMTP                             monitor are as follows:
                                                                      1) Multiple channels to monitor phase, neutral and
 Switching surge studies                                                   ground simultaneously
  tine energizing              I     Arrester duty                    2) Voltage and current measurements
  Single pole switching        I     Insulation                 1     3) Waveform display

     High-speed relcosing
                                                                      4) Continuous monitoring
                                                                      5) Harmonic analysis
                                                                      6) Scopemode
                               I    operation                         7) Simultaneous display of current and voltage wave
  Capacitor switching          I    Ferroresonance                        forms
                                                                      8) Wide frequency response
  Fault clearing

  Transformer switching
                               II   Parallel
                                    Motor starting
                                                                I     9) Event summaries to provide graphical plots o RMS
                                                                           and high frequency events

  Reactor switching            I    Harmonic                          10) Capability to access the monitor over the internet
                                                                       The power monitor should be placed a the location
                                                                      selected in the test plan. To determine the overall power
                                                                      quality of the facility, place a monitor at the service
                                                                      entrance. To investigate a power quality test response for
                                                                      a new manufacturing unit or for single new piece of
                                                                      equipment, place a monitor as close to the unit in question
                                                                      as possible. It will be necessary to record current, voltage
                                                                      and the response of the facility or new equipment over the
B. initial Site Survey
                                                                      period of time of each test segment.
 The initial site survey is used to develop basic information                       IV.   MmGATlON EQUIPMENT
for the PQ study.
1) The nature of the problem is determined, insofar as                 Mitigation equipment exists for each of the above power
      possible.                                                       quality problem categories: voltage transients, voltage
2) An equipment list is made up with as many i d e n t i n g          sags, interruptions, regulation, harmonics, flicker and
      characteristics listed as available, such as plant
                                                                      voltage unbalance. Some of this equipment is listed in
      identification name o number, nameplate information,
                                                                      Table 3.
      rating in amperes, voltage, kilowatts, manufacturer,
      model number, serial number.
                                                                    A.    LQhfning and surge anesters
3) ldentlfy time of day when problems occur. Identify any
     coincident problems or simultaneous operations.
                                                                       Arresters are designed for lightning protection of
4) Determine how the equipment is tied into the plant
                                                                      transformers and are not sufficiently voltage-limiting for
     electrical system.       Identify any existing power

                                                            - 284 -
protecting sensitive electronic control circuits from voltage           magnet energy storage (SMES), storage capacitors or
surges.                                                                 even flywheels driving dc generators. The output of these
                                                                        devices is supplied to the system through an inverter, on a
B.      Thyristor-BasedStatic Switch                                    momentary basis, by a fast acting electronic switch.
                                                                        Enough energy is fed to the system to replace the energy
 The static switch is a versatile device for switching a new            that would be lost by the voltage sag or interruption
element into the circuit when voltage support is needed. It
has a dynamic response time of about one cycle. To                      D. Dynamic Voltage RegulatorEkctmnk Tap Changing
correct quickly for voltage spikes, sags or interruptions the              Transformer
static switch can be used to switch in one of the following:
1) Capacitor                                                             A yoltageregulating transformer with an electronic load
2) Filter                                                               tapchanger is used with a single line from the utility. It
3) Alternate Power line                                                 regulates voltage drops up to 50%.        It requires a stii
4) Energy Storage System                                                system (short-circuit power to load ratio of 1O:l or better).
  The static switch can be used in the alternate power line             This has coarse steps and is intended for only occasional
application. This scheme requires two independent power                 voltage variations.
lines from the utility. It protects against 85% of the
interruptions and voltage sags. It does not protect against             E. Static Var Compensators
area-wide voltage disturbancesthat affect both lines.
                                                                         Loads such as rolling mills, mine hoists, cranes, welding
                               TABLE 3                                  machine and arc furnaces, where the use of reactive power
               POWER QUALITY MITIGATION EQUIPMENT                       changes instantaneously, often cause rapid voltage
                                                                        fluctuations. If the effects are sufficiently large. production
I Problem                  I Mitigation Device                          or operational disturbances can result. This type of voltage
 Voltage Transient         I                                            variation can be controlled with reactive power
    Spike                  1   Surge Arresters                          compensation. Equipment is available in size ranges from
I Oscillation              I Liahtnina Arresters                I       1 to 100 MVAR. This equipment utilizes a combination o        f
                           I Staticswitch                               reactors, capacitors and, depending on the response time
                           I   Controlled Switching                     needed, thyristor or IGBT-based controls.
I                          1 Energy Storage Systems             I       F. Passive H a m n i c Fitters

                                                                         Filters are used in some instances to effectively reduce or
                             Automatic Tap                              eliminate certain harmonics. If possible, it is always pre-
                             Changing Transformer                       ferable to use a 12-pulse o higher pulse transformer con-
                           I DynamicVoltage Regulator                   nection rather than a filter. Tuned harmonic filters should
                                                                        be used with caution, and avoided, when possible.
                           [ Static Var Compensator                     Usually, multiple filters are needed, each tuned to a
    Voltage Interruption                                                separate harmonic. Each filter causes a parallel resonance
       Momentary               Energy Storage Systems                   as well as a series resonance, and each filter slightly
       Sustained               Static Swiich                            changes the resonances of other filters.               Parallel
                               Automatic Tapchanging Transf.            resonances can occur near system harmonic frequencies
                               DynamicVoltage Regulator                 exacerbating an existing problem, or they can excite inter-
                               Static Var Compensator                   harmonics. If the use of passive tuned harmonic filters is
    Reaulation                                                          anticipated, the power quality study is definitely needed to
      Overvoltage              Automatic Tapchanging Transf.            explore all the ramifications of using this equipment.
      Undervoltage             Dynamic Voltage Regulator
                               Static Var Comoensator                   G. Modified CBEMA Curve
I Harmonics.               I                                    I
I   Notching, Noise                                                      EPRI, Canadian Electric Assoc. (CEA) and National Power
                               Passive Filter                           Laboratory (NPL) have assembled and combined their field
                               Dynamic Filter                           data on voltage sags, spikes and interruptions. Figure 11,
                               Static Var Comoensator                   has been prepared using this information. It shows the
     Flicker                                                            annual distribution of power quality aberrations for a typical
                           I   Static Var Compensator                   industrial site. Based on this study, the Information
                                                                        Technology Industry Council (ITIC). formerly CBEMA, in
    C. Energy Storage Systems                                           1996 modified the well-known CEBEMA curve to the shape
                                                                        shown in Figure 12.
Storage systems can be used to protect sensitive
production equipment from shutdowns caused by voltage
sags or momentary interruptions. These are usually dc
storage systems, such as UPS, batteries, superconducting

                                                                - 285   -
                                                                              at the control voltage level. The lower voltage and smaller
                                                                              kVA corrections are much less expensive than corrections
                                                                              at the transmission voltage level. Appendix A provides
                                                                              results of interviews with engineers of a number of
                                                                              industries on their views of power quality mitigation.
                                                                                V. HOW TO APPROACH THE AQUlSTlON OF NEW
                                                            6%                 PROCESS EQUIPMENT FROM THE W PERSPECTIVE
                                                                                From this background review of the power quality issues,
                                                                              how do we approach the preparation of process equipment
                   aoiwo amwo           Duslpn                                specifications for industrial equipment that will preclude
                                                                              power quality problems when the equipment is placed in
                              Figure 11                                       service, and later throughout its operating life?
                             PQ Field Data                                      The equipment must be made to be tolerant of power
                                                                              quality voltage aberrations and not produce harmonics in
                                                                              excess on IEEE Standard 519, considering quantity of
                                     110 Volt Equlpmant                       equipment and the point of common coupling. Some
                                                                              knowledge of the power system and the industrial facility is
                                                                              obviously needed.         The utility may have historical
             z                                                                information on the frequency of voltage sags, momentary
             5   200
                                                                              interruptions, and interruptions on the circuit or circuits
             f                                                                being considered for supplying the facility. Before the
              ; 1m
             '     70
                                                                              equipment is specified, preliminary engineering needs to be
                                                                              done. This will prevent much grief later on. Preliminary
                     0      0.01 5   J m      0.0.
                                                                              information needs to be obtained from the utillty, from the
                               tm          20m       10.                      proposed equipment suppliers, assuming that there is more
                         DumUon in C y c l r and S.cond.
                                                                              than one and competitive bidding is anticipated. If
                          Figure 12                                           partnering is expected, preliminary infomation is still
                   Modified CEBEMA Curve                                      needed.
                                                                                It is recommended that a power quality study be made of
 The modified CEBEMA curve shows the power quality                            the facility, or of the proposed facility, if it is a new one.
withstand goal of equipment manufacturers in this                             This will involve modeling the utility system, the industrial
computer-related industry. Other industries are now                           plant's electric supply system, and the new equipment
evaluating the use of this curve as a standard for power                      using a program such as EMTP.
quality-withstand tolerance. The following capability values                    The following historical data from the past few years, for
have been picked from this new curve:                                         each supply circuit is obtained from the utility:
 Momentary Interruption 0 volts for 20 ms                                     1) Interruptions, average annual number.
 Vottage Sag - 70% volts for 0.5 seconds                                      2) Momentary Interruptions, average annual number.
                    80% volts for I O seconds                                 3) Voltage sags, average annual number, and percent
                    90% volts continuous                                             sag.
 Voltage Spike 500% volts for 0.01 cyde                                       4) Voltage level range, maximum and minimum.
                      200% volts for 1 psec.                                  5) Ambient level of harmonics, THD value for each
                      120% volts for 0.5 seconds                                     harmonic.
                      110% volts continuous                                   6) Minimum short-arcuit kVA or MVA at the point of
                                                                                     common coupling.
H. CVTs and Coil HoM-in Devices                                               7) ldenttfy any capacitors on the proposed supply circuit
                                                                                    or circuits. Are the capacitors switched for voltage
 For many power quality studies, it is possible to greatly                           control?
improve the sag and momentary interruption tolerance of a                     8) Single line diagram of the utility supply system
facility by protecting control circuits. Constant-voltage                           showing power generation sources, transformers with
transformers, CvTs, can be used on control circuits to                               impedances and capacitors.
provide constant voltage with 3 cycle ride-through, or relays                   The following information is to be obtained from the
and ac contactors can be provided with electronic coil hold-                  industrial system:
in devices to prevent misoperation from either low or                         1) Single line diagram of plant electric system induding
interrupted voltage.                                                                transformers, circuit breakers, and capacitors.
                                                                              2) Any harmonic producing equipment, such as rectifiers,
I.   ApplicabiMy                                                                    ASDs, or other.
                                                                              3) Any power quallty mitigation equipment.
 Some of this equipment is more applicable to mitigation at                   4) If the equipment is to be added to an existing plant,
the transmission voltage level; others are more appropriate                          harmonic measurements on each supply bus and at
at the 480 volt bus or motor control center level, and some                         the point of common coupling.

                                                                  - 286   -
5)  5) Identify any large motors that are started acrossthe-                                      TABLE 4
    line, voltage and horsepower.                                                           PQ DESIGN CHECKLIST
This information is to be determined from the power quality
study:                                                                   Item                       1. I
                                                                                                     I          Responsibility   I   I
1) Voltage sag study: expected voltage sag level from                    Power Quality Study -      I       I   Customer
    line-to-line faults, from line-to-ground faults, and from
    motor starting.                                                        Saas
                                                                                                    I       1                    I       II
2) Expected duration or any momentary interruptions, in
    cycles.                                                                 Interruptions           I       I                    I        I
3) Level of voltage spikes to be expected from any
    capacitor switching or from circuit breaker operations
    on the u t i l i system.
4) Expected harmonic levels from adding the new
5) Any potential electric harmonic resonances.

A. Equipment Specification

The new process equipment specification needs address
the reliability of the equipment. Reliability should not be
compromised by power quality problems, and                the
equipment should not cause power quality problems, e.g.
harmonics in excess of IEEE Std. 519 recommendations,
or EMVRFI radiation sufficient to cause any reliability
problems. The specification should request a $year
guarantee against shutdown from any power quality
problem based on specified expected power quality
characteristics of the power supply.
  Based on information obtained from the Power Quality
Study, the specification should specify expected values for
the following:
1) Voltage sags, amplitude and duration.
2) Momentary interruptions, amplitude and duration.
3) Voltage spike amplitudes.
4) Ambient harmonic level.                                                   Warranty
5) Expected circuit resonant frequencies.                                   Utility Single Line
  The specification should include single-line diagrams of               Diag.
the utility power supply and of the proposed industrial plant,              Plant single Line
with the point of common coupling identified. The minimum                Diag.                      I
available short circuit MVA from the utility at the point of                Info. Furnish
common coupling needs to be specified. If any ASDs are                   w/Proposal
induded in the equipment being purchased, the                               Short CM. MVA at
specification should address limits on the kVA rating of                 PCC
equipment as regards Spulse and 12-pulse units and                          Ambient Harmonics
allowable THD limits from the ASDs.
  The specification should specify the tests that should be              bearing failures from inverter output voltage
carried out by the vendor to demonstrate compliance with                 characteristics.
the power quality tolerance of the equipment to the                   The vendor should fumish with his proposal a statement
specified system power quality characteristics.                      of warranty regarding equipment reliability of operation
  Under information to be furnished with the proposal, in            considering the specified expected system power quality
addition to the technical information on the performance of          characteristics. He should specify the tests he will perform
the equipment, there should be the following power quality           during commissioning to verify the reliability of the
information:                                                         equipment to the specified system power quality
 1) Preliminary harmonic study results: voltage and current          characteristics
     THD harmonic levels at the point of common coupling.
2) Preliminary EMTP study results, defining voltage sag                    VI. CHECKLIST OF PROCEDURES FOR DESIGN,
     levels and frequency, momentary interruption duration                         INSTALLATION, AND TESTING
     and frequency, voltage spike amplitude and frequency
     of occurrence.                                                    These checklists, Tables 4, 5, and 6, will help the utility
3) If ASDs and motors are part of the equipment                      industrial customer through the design, installation, and
     package, the vendor should address the n o n                    testing phases of the new process equipment acquisition
     susceptibility of the motors to winding failures or

                                                             - 287   -
from the point of view of eliminating later power quality               I ) Voltage sag
problems.                                                               2) Voltage unbalance
                       TABLE 5                                          3) Voltage swell
       PQ CHECKLIST FOR EQUIPMENT INSTALLATION                          4) Low steady-state voltage
                                                                        To simulate a voltage interruption, the supply breaker is
                                                                        opened and closed. If there is a utility mpaator bank in the
                                                                        region of test site, the effect of capacitor switching transient
                                                                        could be observed with the power quality monitor.

                                                                                           VIII.   CONCLUSIONS

                                                                        Understanding the Power Quality issue leads to a systems
                                                                        approach to the acquisition of new process equipment as
                                                                        regards its tolerance to power quality aberrations.
                                                                        Equipment specifications are designed to make production
                                                                        equipment Po tolerant. To prepare these specrfications
                                                                        correctly, a power quality study is needed to determine
                                                                        what can be expected from both electric utility power
                                                                        quality and internal facility power quality when the new
                                                                        equipment is placed into service. Post startup testing for
                                                                        equipment tolerance to power quality aberrations may be
                            TABLE 6                                     appropriate.
                 CHECKLJST FOR PQ TESTS
                                                                                            IX     REFERENCES
I Item                  I J      I ResDonsibilitv      IJ         I
I Test Procedure        I        I Plant               I          II    The following documents provide support to information
I                       I        I                     I                contained in this paper as well as supplementary material
  Test Technicians              ' I Equip't Supplier   1                beyond the scope of this paper.
  Test Equipment      I           I Equip't Supplier   I
I Test Schedule       I           I EauiD't Sumlier    I          I            ABB Industrial Power Quality Seminar. Dr. Le Tang
  Equipment                         Plant                                      and John Daniel, Turgi, Switzerland. April 26-28,
  Availability                                                                 1999.
  Coordination-Plant/                Plant                                     Efectric       Power      Systems  Quality,    Dugan,
  Utilitykquip't                                                               McGranaghan,            Beaty. McGrawHill, New York,
, Supplier                                                                     1996.
                                                                               'Trouble-Shooting Guide for LowVoltage ASDlMotor
     VII.   NEW PROCESS EQUIPMENT TEST PLAN                                    Systems". EPRl TR-111097, Jarsco Engineering Corp.
                                                                               Final Report November 1998
  Working with the electric u t i l i and utilizing available                  "The Power Quality Survey". NETA World, Summer
portable test rig facilities to simulate the power quality                     1998. Richard Bingham, Dranetz-BMI, Edison, New
anomalies, a test plan is made for verifying the                               Jersey.
performance of the new equipment installation as regards                       "Superconductiong Magnet Energy Storage Smooths
susceptibility to power quality disruptions. Depending on                      Voltage Sags". Maintenance Technology, May, 1999.
test rig capability and the availability of any utility voltage                "Solutions for Power Quality". ABB Power Systems
control capacitors near the industrial facility, it may be                     'TCSC - Thyristor Controlled Series Capacitors. ABB
possible to test for the new equipment response to the                         Power Systems.
following:                                                                     W e don't have a flicker problem...' ABB Power
1) Voltage sag of specified amount and duration                                systems.
2) Unbalanced phase voltage of specified amount                                 "Minimum flicker, optimum active power and..." ABB
3) Low steady-state voltage of specified amount                                Power Systems.
4) Response to capacitor switching transient voltage                      10) "The Electromagnetic Transients Program - EMTP".
5) Voltage interruption                                                 htt~://www.      electrotek.com.
 The test plan indudes written procedures for each                        11) 'SuperHarm@' Harmonic Simulation Software.
simulation describing the test rig set-up and the monitoring            h t t p : / / w .electrotek.com.
equipment to be used.                                                    12) 'HarmFlo+ Workstation for Windows.
  Portable power quality test simulators are available for              httD://www. electrotek.com.
rent along with technicians. At the 100 ampere, 480 volt                13) " PSCAD@/EMTDC" Powerful Transients Simulation
and 200 ampere, 480 volt level. The 100 ampere                          Software by Manitoba HVDC Research Centre.
equipment is intended for component testing. The 200                    http://www.electrotek.com.
ampere equipment is intended for use at the motor control               14) WebPASS7M Web Monitoring of Power Quality Data
center.     These devices can simulate the following                    from BMI 8010 and 8020 PQNodesB.
anomalies:                                                              http://www.electrotek.com.

                                                              - 288 -
15) "fQWeb@ Monitoring Power Quality via World Wide                understanding of what the power quality issues are, and
Web". htttxilwww.electrotek.a m .                                  how to correct the problems. Manufacturing industries are
16) TOP, The Output Processor@Power System Ana/ysjs                using more and more ASDs for energy savings to reduce
and Display Software". http:/IWWW.electratek.com.                  the cost of electricity. They know that AS& can produce
17) ' W V i e W Power Quality Database Management and              harmonics to the systems and to the motor. They also
Analysis Software" h t t r x / / w .electrotek.com.                know about using input transformers and input reactors in
18) WebPES- Web Monitoring of Data from Dranetz-BMI                conjunction with ASDs to prevent tripping on voltage
7100 PQNodes@and PQPagersO".                                       spikes, and to control harmonics to the system. They use
httD://www.electrotek.com.                                         shielded control cable to control EMI.
19) "Fluke VRllOlS Voltage Event recorder System".                   These engineers are under strict cost controls. Any W
http://www.fluke.com.                                              mitigation devices must meet economic payback criteria.
20) "Application of CFilters in Steel Mill Power Systems".         They prefer to design the ASD installation correctly in the
Rory Dwyer, Le Tang ABB Electric systems Technology                first place, rather than later resorting to PQ mitigation
Institute, Steve G. Ashmore, ABB HV Capacitor Div.                 activities. In most cases, they have the ability and
21) "Harmonic Interaction Between 1500-kVA Supply                  persistence to get to the root cause of the problem. There
Transformer and W D Load at an Industrial Plant". Mahesh           is a tendency for many of these firms to somehow acquire
M Swamy, Steven L. Rossiter. Paper ICPSD 97-20. 1997               low-cost, substandard electric motors in vendor packages
Industrial and Commercial Power Systems Technical                  for new projects. These motors do not last long and are
Conference, Philadelphia. May 12-15, 1997.                         generally replaced with motors with cast iron frames and
                                                                   with inverter grade windings.
                         x   VlTA                                    Most feel that they get good quality power from the utility,
                                                                   and that the utility does a good job in making Power Quality
 James A. Oliver holds degrees of BSEE, University of              training available.
Maine and MEE, Polytechnic University. After career                  Smaller, less-well-financed manufacturing companies
segments with American Electric Power, McGraw Edison,              have power quality problems, but they may not recognize
and Bechtel Corp. he is now President of J a m                     them as such. They have shut downs, but unless they are
Engineering Corp. where he works on motor, generator,                                                                f
                                                                   of really significant duration, they take care o the problem
adjustable-speed drive, dist-ributed generation and power          and restart the operation. A few of the comments by
quality issues. He has been active in establishing the IEEE        specific industries follow:
International Machines and Drives Conference and he is an           1) Power Qualify Equipment Supplier and Consultant In
IEEE Fellow. In 1998, he received the IEEE Richard Harold          conducting a PQ audit, this interviewer looks for the simple,
Kaufmann Award.                                                    easy-to-identrfy things first. His procedure:
 Roger Lawrence graduated from Imperial College, London            1) walk-through
University, with BSEE and ACGl degrees. He received his            2) Identify the problem, induding monitoring
MBA degree from Mercer University. He spent 26 years               3) determine the costlbenefd
with GEC designing and developing power electronic                   Sometimes the solution is too costly to consider. By
equipment, and 7 years with EPRl's Adjustablespeed                 placing the mitigation equipment as dose to the problem as
Drive Application Oftice (ASDO). He is presently Vice-             possible, the costs can usually be minimized. Management
President of the EPRl ASDO.                                        will not consider the mitigation project, unless a detailed
 Basudeb Ben Banerjee has a BSEE degree from                       ROI is included.
University of Calcutta and a MEE degree from the                   2)      Automfive Finish Manufacturing More and more
University of South Carolina. He was formerly engineering          ASDs are being used for energy conservation. They are
manager for Square D Company in Columbia, SC, working              careful to design the ASD installation with input
with ASDs, and MCCs. Now Ben is Power Electronics                  transformers, input reactors, or filters as needed for
Manager for Power Cond-itioning and Energy Storage in              troublefree, reliable operation. They are careful about
the Science, Technology and Development Division of                specifying ASD sag and interruption ride-through capability.
EPRl. A member of IEEE, he has participated in IEEE and            3) Polyester Film Manufacturing Ten or twelve years ago
NEMA standards work. He initiated and directs the EPRI-            they applied low speed flywheel generators to back-up the
sponsored National Motors and Drives Steering                      power supply to their extruders and melt pumps to provide
Committee.                                                         ride-through capability for vottage interruptions. They have
                                                                    no specific problems now.
                  APPENDIX                                         4) Photographic Paper Manufaduring This facility
                                                                         generates 90% of its own power and purchases 10%.
                                                                         An outage of the machine creates a penalty of $1
                                                                         million per day, so they have been careful in designing
  To find out first hand what the industrial manufacturing               their ASD installations to minimize harmonics to their
community's concerns are about Power Quality, a series of                distribution system. They were concerned about
interviews were conducted with maintenance and industrial                lightningcreated voltage spikes on the utilq supply
engineers in manufacturing facilities throughout the                     getting into their electric system, so they are now using
country. These interviews yielded a variety of insights.                 lightning arresters with better protective characteristics.
  As a general observation, large, well-established industrial           Also, they have placed much of their power distribution
manufacturing firms make power quality training available                system underground.
to their engineering staff. Their engineers have an

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