Appendix 1-454-465

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A p p e n d i x 1T e r m i n o l o g y

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The introduction of computer technology means that theProtection Engineer must now be familiar with a rangeof technical terms in this field, in addition to the termslong associated with Protection and Control. Below is a

list of terms and their meanings that are now commonlyencountered in the Protection and Control field.

ACAlternating Current

ACBAir Circuit Breaker

AccuracyThe accuracy of a transducer is defined by the limits of intrinsic error and by the limits of variations.

Accuracy c lass

A number used to indicate the accuracy range of ameasurement transducer, according to a definedstandard.

Act ive power (watt ) t ransducerA transducer used for the measurement of activeelectrical power

ADCAnalogue to Digital Converter

A/D Convers ionThe process of converting an analogue signal into an

equivalent digital one, involving the use of an analogueto digital converter

AdjustmentThe operation intended to bring a transducer into a stateof performance suitable for its use

AGCAutomatic Gain Control

AIAnalogue Input

AISAir Insulated Switchgear

Appendix 1Term in ology

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AlarmAn alarm is any event (see below) tagged as an alarmduring the configuration phase

Al l-or-nothing re layAn electrical relay which is intended to be energised bya quantity, whose value is either higher than that atwhich it picks up or lower than that at which it drops out

Ant i-pumping deviceA feature incorporated in a Circuit Breaker or reclosingscheme to prevent repeated operation where the closingimpulse lasts longer than the sum of the relay and CBoperating times

AOAnalogue Output

ARAuto Reclose: A function associated with CB,implemented to carry out reclosure automatically to try

to clear a transient faultARBITERProprietary protocol for time synchronisation fromARBITER Systems, Inc. Paso Robles, California USA

Arcing t imeThe time between instant of separation of the CBcontacts and the instant of arc extinction

Auto-t ransformerA power transformer that does not provide galvanicisolation between primary and secondary windings

AUXAuxiliary

Auxi l ia ry c i rcu i tA circuit which is usually energised by the auxiliarysupply but is sometimes energised by the measuredquantity

Auxi l ia ry re layAn all-or-nothing relay energised via another relay, forexample a measuring relay, for the purpose of providinghigher rated contacts, or introducing a time delay, or

providing multiple outputs from a single input.Auxi l ia ry supplyAn a.c. or d.c. electrical supply other than the measuredquantity which is necessary for the correct operation of the transducer

AVRAutomatic Voltage Regulator

Back-up protect ionA protection system intended to supplement the mainprotection in case the latter should be ineffective, or to

deal with faults in those parts of the power system thatare not readily included in the operating zones of themain protection

BaySet of LV, MV, or HV plant and devices, usually controlledby a bay computer

BCBay Computer. Computer dedicated to the control of oneor several bays within a substation

BCD

Binary Coded Decimal

BCPBay Control Point. A local keypad at bay level to controlthe elements of a single bay

Biased re layA relay in which the characteristics are modified by theintroduction of some quantity other than the actuatingquantity, and which is usually in opposition to theactuating quantity

Bias current

The current used as a bias quantity in a biased relay

BIOSBasic Input/Output System (of a computer ormicroprocessor)

BTBooster Transformer

Booster TransformerA current transformer whose primary winding is in serieswith the catenary and secondary winding in the returnconductor of a classically-fed a.c. overhead electrified

railway. Used at intervals to ensure that stray tractionreturn currents, with their potential to causeinterference in nearby communication circuits, areminimised

BurdenThe loading imposed by the circuits of the relay on theenergising power source or sources, expressed as theproduct of voltage and current (volt-amperes, or watts if d.c.) for a given condition, which may be either at‘setting’ or at rated current or voltage. The rated outputof measuring transformers, expressed in VA, is always atrated current or voltage and it is important, in assessingthe burden imposed by a relay, to ensure that the valueof burden at rated current is used

CCapacitance

CADComputer Aided Design

Cal ibrat ionThe set of operations which establish, under specifiedconditions, the relationship between values indicated bya transducer and the corresponding values of a quantityrealized by a reference standard. (This should not beconfused with ‘adjustment’, q.v.)

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CBCircuit Breaker

CBCCompact Bay Controller. Small capacity bay computerfor Medium Voltage applications

CBCTCore Balance Current Transformer

CCRCentral Control Room

CDMConceptual Data Modelling is an activity whose aims are:

• to define objects and links and naming conventions fortheir identifications

• to guarantee interoperability between subsystems

• to define standard exchange formats between systemconfigurator and subsystem configurators

Character i s t ic angleThe angle between the vectors representing two of theenergising quantities applied to a relay and used for thedeclaration of the performance of the relay

Character i s t ic curveThe curve showing the operating value of thecharacteristic quantity corresponding to various valuesor combinations of the energising quantities

Character i s t ic Impedance Rat io (C . I .R . )The maximum value of the System Impedance Ratio up

to which the relay performance remains within theprescribed limits of accuracy

Character ist ic quantityA quantity, the value of which characterises theoperation of the relay, for example, current for anovercurrent relay, voltage for a voltage relay, phase anglefor a directional relay, time for an independent timedelay relay, impedance for an impedance relay

Check protect ion systemAn auxiliary protection system intended to prevent

tripping due to inadvertent operation of the mainprotection system

CHPCombined Heat and Power

Circuit insulat ion voltageThe highest circuit voltage to earth on which a circuit of a transducer may be used and which determines itsvoltage test

Class indexThe number which designates the accuracy class

Clos ing Impulse t imeThe time during which a closing impulse is given to theCB

Clos ing T imeThe time for a CB to close, from the time of energisationof the closing circuit to making of the CB contacts

C o mp l ia nc e v o lt ag e ( a cc ur a cy l i m it in goutput vo l tage)For current output signals only, the output voltage up towhich the transducer meets its accuracy specification

Conjunct ive testA test of a protection system including all relevantcomponents and ancillary equipment appropriatelyinterconnected. The test may be parametric or specific

Convers ion coeff ic ientThe relationship of the value of the measurand to thecorresponding value of the output

Core Ba lance Current TransformerA ring-type Current Transformer in which all primaryconductors are passed through the aperture of the CBCT.

Hence the secondary current is proportional only to anyimbalance in current. Used for sensitive earth-faultprotection

Count ing RelayA relay that counts the number of times it is energisedand actuates an output after a desired count has beenreached.

CSV Character (or Comma) Separated Values format. Awidely used format for the exchange of data betweendifferent software, in which the individual data items aseparated by a known character – usually a comma

CTCurrent Transformer

Current t ransducerA transducer used for the measurement of a.c. current

CVTCapacitor Voltage Transformer. A voltage transformerthat uses capacitors to obtain a voltage divider effect.Used at EHV voltages instead of an electromagnetic VTfor size/cost reasons

DACDigital to Analogue Converter

DARDelayed auto-reclose

DATDigital Audio Tape

DBMSData Base Management system

DCF77

LF transmitter located at Mainflingen, Germany,broadcasting a time signal on a 77.5kHz frequency

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DCPDevice Control Point: local keypad on device level tocontrol the switchgear, often combined withlocal/remote switch

DCSDistributed Control System

Dead T ime (auto-rec lose)

The time between the fault arc being extinguished andthe CB contacts re-making

De-ionisat ion t ime (auto-reclose)The time required for dispersion of ionised air after afault is cleared so that the arc will not re-strike on re-energisation

Delayed Auto-Rec loseAn auto-reclosing scheme which has a time delay inexcess of the minimum required for successful operation

Dependent t ime measur ing re lay

A measuring relay for which times depend, in a specifiedmanner, on the value of the characteristic quantity

DFTDiscrete Fourier Transform

Digi ta l S ignal ProcessorA microprocessor optimised in both hardwarearchitecture and software instruction set for theprocessing of analogue signals digitally, through use of the DFT and similar techniques

Digi ta l S ignal Process ing

A technique for the processing of digital signals byvarious filter algorithms to obtain some desiredcharacteristics in the output. The input signal to theprocessing algorithm is usually the digital representationof an analogue signal, obtained by A/D conversion

Direct ional re layA protection relay in which the tripping decision isdependent in part upon the direction in which themeasured quantity is flowing

Discr iminat ion

The ability of a protection system to distinguish betweenpower system conditions for which it is intended tooperate and those for which it is not intended to operate

Distort ion factorThe ratio of the r.m.s. value of the harmonic content tothe r.m.s. value of the non-sinusoidal quantity

DNPDistributed Network Protocol. A proprietarycommunication protocol used on secondary networksbetween HMI, substation computers or Bay Computersand protective devices

DOLDirect-on-Line

Direct-on-LineA method of motor starting, in which full line voltage isapplied to a stationary motor

Drop-out (or drop-off )A relay drops out when it moves from the energisedposition to the un-energised position

Drop-out/pick-up rat io

The ratio of the limiting values of the characteristicquantity at which the relay resets and operates. Thisvalue is sometimes called the differential of the relay

DSPDigital Signal Processing

DTDefinite time

Earth fau l t protect ion systemA protection system which is designed to respond only tofaults to earth

Earthing transformerA three-phase transformer intended essentially toprovide a neutral point to a power system for thepurpose of earthing

Effect ive rangeThe range of values of the characteristic quantity orquantities, or of the energising quantities to which therelay will respond and satisfy the requirementsconcerning it, in particular those concerning precision

Effect ive set t ing

The ‘setting’ of a protection system including the effectsof current transformers. The effective setting can beexpressed in terms of primary current or secondarycurrent from the current transformers and is sodesignated as appropriate

Elect r i ca l re layA device designed to produce sudden predeterminedchanges in one or more electrical circuits after theappearance of certain conditions in the electrical circuitor circuits controlling it

NOTE: The term ‘relay’ includes all the ancillaryequipment calibrated with the device

Elect romechanica l re layAn electrical relay in which the designed response isdeveloped by the relative movement of mechanicalelements under the action of a current in the inputcircuit

EMCElectro-Magnetic Compatibility

Embedded generat ion

Generation that is connected to a distribution system(possibly at LV instead of HV) and hence poses particularproblems in respect of electrical protection

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e .m.f .Electro-motive Force ( or voltage)

Energis ing quantityThe electrical quantity, either current or voltage, whichalong or in combination with other energising quantities,must be applied to the relay to cause it to function

EPROM

Electrically Programmable Read Only Memory

Error (of a t ransducer)The actual value of the output minus the intended valueof the output, expressed algebraically

EventAn event is any information acquired or produced by thedigital control system

FATFactory Acceptance Test. Validation procedureswitnessed by the customer at the factory

Fault Passage IndicatorA sensor that detects the passage of current in excess of a set value (i.e. current due to a fault) at the location of the sensor. Hence, it indicates that the fault liesdownstream of the sensor

FBDFunctional Block Diagram: One of the IEC 61131-3programming languages

Fiduc ia l va lueA clearly specified value to which reference is made in

order to specify the accuracy of a transducer. (Fortransducers, the fiducial value is the span, except fortransducers having a reversible and symmetrical outputwhen the fiducial value may be either the span or half the span as specified by the manufacturer. It is stillcommon practice, however, for statements of accuracyfor frequency transducers to refer to ‘percent of centre-scale frequency’ and, for phase angle transducers, to anerror in electrical degrees.)

FPIFault Passage Indicator

Frequency t ransducerA transducer used for the measurement of the frequencyof an a.c. electrical quantity

Ful l duplex communicat ionsA communications system in which data can travelsimultaneously in both directions

GatewayThe Gateway is a computer which provides interfacesbetween the local computer system and one or severalSCADA (or RCC) systems

GISGas Insulated Switchgear (usually SF6)

Global Posit ioning SystemA system used for locating objects on Earth precisely,using a system of satellites in geostationary orbit inSpace. Used by some numerical relays to obtain accuratetime information

GMTGreenwich Mean Time

GPSGlobal Positioning System

GTOGate Turn-off Thyristor

Half- duplex communicat ionsA communications system in which data can travel inboth directions, but only in one direction at a time

High-speed rec los ingA reclosing scheme where re-closure is carried outwithout any time delay other than that required for de-

ionisation, etc.

HMIHuman Machine Interface. The means by which a humaninputs data to and receives data from a computer-basedsystem. Usually takes the form of a Personal Computer(PC) (desktop or portable) with keyboard, screen andpointing device

HRCHigh Rupturing Capacity (applicable to fuses)

HSR

High Speed Reclosing

HV High Voltage

HVDCHigh Voltage Direct Current

ICurrent

ICCPTerm used for IEC 60870-6-603 protocol

ICTInterposing Current Transformer (software implemented)

I .D.M.T.Inverse Definite Minimum Time

IGBTInsulated Gate Bipolar Transistor

I /OInput/Output

IED

Intelligent Electronic Device. Equipment containing amicroprocessor and software used to implement one ormore functions in relation to an item of electrical

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equipment (e.g. a bay controller, remote SCADAinterface/protocol converter). A microprocessor-basednumerical relay is also an IED. IED is a generic term usedto describe any microprocessor-based equipment, apartfrom a computer

IGBTInsulated Gate Bipolar Transistor

Independent t ime measur ing re layA measuring relay, the specified time for which can beconsidered as being independent, within specified limits,of the value of the characteristic quantity

Inf luence quantityA quantity which is not the subject of the measurementbut which influences the value of the output signal for aconstant value of the measurand

Input quantityThe quantity, or one of the quantities, which constitute

the signals received by the transducer from the measuredsystem

Instantaneous re layA relay that operates and resets with no intentional timedelay.

NOTE: All relays require some time to operate; it ispossible, within the above definition, to discuss theoperating time characteristics of an instantaneous relay

Insulated Gate Bipolar TransistorA special design of transistor that is suitable for handling

high voltages and currents (relative to an ordinarytransistor). Frequently used in static power controlequipment (inverters, controlled rectifiers, etc) due to theflexibility of control of the output

In t r ins ic er rorAn error determined when the transducer is underreference conditions

Inverse t ime delay re layA dependent time delay relay having an operating timewhich is an inverse function of the electricalcharacteristic quantity

Inverse t ime re lay with def in i te min imumtime ( I .D.M.T.)An inverse time relay having an operating time thattends towards a minimum value with increasing valuesof the electrical characteristic quantity

IR IG-BAn international standard for time synchronisation

ISOInternational Standards Organisation

K-bus (K-bus Cour ier )Term used for the Courier protocol on K-Bus interface forK-Relay range manufactured by AREVA

Knee-point e .m.f .That sinusoidal e.m.f. applied to the secondary terminalsof a current transformer, which, when increased by 10%,causes the exciting current to increase by 50%

LInductance

LAN

Local Area Network

LCDLiquid Crystal Display

LEDLight Emitting Diode

LDLadder Diagram. One of the IEC 61131-3 programminglanguages

LDC

Line drop compensatorLimit ing value of the output currentThe upper limit of output current which cannot, bydesign, be exceeded under any conditions

Loca l Contro l ModeWhen set for a given control point it means that thecommands can be issued from this point

Lock-out (auto-rec lose)Prevention of a CB reclosing after tripping

Long-term stabi l i ty

The stability over a period of one year

Low-speed auto-rec loseSee Delayed Auto-Reclose

LV Low Voltage

Main protect ionThe protection system which is normally expected tooperate in response to a fault in the protected zone

Maximum permissible values of the inputcurrent and vol tage

Values of current and voltage assigned by themanufacturer which the transducer will withstandindefinitely without damage

MCBMiniature Circuit Breaker

MCCBMoulded Case Circuit Breaker

Mean-sens ing t ransducerA transducer which actually measures the mean

(average) value of the input waveform but which isadjusted to give an output corresponding to the r.m.s.value of the input when that input is sinusoidal

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MeasurandA quantity subjected to measurement

Measur ing e lementA unit or module of a transducer which converts the

measurand, or part of the measurand, into a

corresponding signal

Measur ing range

That part of the span where the performance complieswith the accuracy requirements

Measur ing re layAn electrical relay intended to switch when its

characteristic quantity, under specified conditions and

with a specified accuracy attains its operating value

Metering (non-tariff) Values computed depending on the values of digital or

analogue inputs during variable periods

Meter ing ( tar i f f )Energy values computed from digital and/or analogue

inputs during variable periods and dedicated to energymeasurement for billing (tariff) purposes

Mid Point Sect ioning Substat ion

A substation located at the electrical interface of twosections of electrified railway. It contains provision for

the coupling of the sections electrically in the event of

loss of supply to one section

ModBusProprietary communication protocol used on secondary

networks between HMI, substation computers or BayComputers and protective devices

MPSSMid Point Sectioning Substation (electrified railways)

Mult i-element transducerA transducer having two or more measuring elements.

The signals from the individual elements are combined toproduce an output signal corresponding to the

measurand

Mult i-sect ion t ransducerA transducer having two or more independent measuring

circuits for one or more functions

Mult i-shot rec los ingA reclosing scheme that permits more than one reclosing

operation of a CB after a fault occurs before lock-out

occurs

MV Medium Voltage

N/C

Normally Closed

N/ONormally Open

Nominal range of useA specified range of values which it is intended that aninfluence quantity can assume without the output signalof the transducer changing by amounts in excess of those specified

Notching relayA relay which switches in response to a specific number

of applied impulsesNPSNegative Phase Sequence

NSNeutral Section (electrified railways)

Numer ica l re layA protection relay which utilises a Digital SignalProcessor to execute the protection algorithms insoftware

OCB

Oil Circuit Breaker

Off-Load Tap ChangerA tap changer that is not designed for operation whilethe transformer is supplying load

OHLOverhead line

OLTCOn Load Tap Changer.

On Load Tap Changer

A tap changer that can be operated while thetransformer is supplying load.

Opening t imeThe time between energisation of a CB trip coil and theinstant of contact parting

Operat ing current (of a re lay)The current at which a relay will pick up

Operat ing t ime (CB)The time between energisation of a CB trip coil and arcextinction

Operat ing t ime ( re lay)With a relay de-energised and in its initial condition, thetime which elapses between the application of acharacteristic quantity and the instant when the relayoperates

Operat ing t ime character i s ti cThe curve depicting the relationship between differentvalues of the characteristic quantity applied to a relayand the corresponding values of operating time

Operat ing va lue

The limiting value of the characteristic quantity at whichthe relay actually operates

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OPGWOptical Ground Wire – a ground wire that includesoptical fibres to provide a communications link

OSI 7- layer modelThe Open Systems Interconnection 7-layer model is amodel developed by ISO for modelling of acommunications network.

Output common mode interference vol tageAn unwanted alternating voltage which exists betweeneach of the output terminals and a reference point

Output current (of a transducer)The current produced by the transducer which is ananalogue function of the measurand

Output loadThe total effective resistance of the circuits andapparatus connected externally across the outputterminals

Output power (of a transducer)The power available at the transducer output terminals

Output ser ies mode interference vol tageAn unwanted alternating voltage appearing in seriesbetween the output terminals and the load

Output s ignalAn analogue or digital representation of the measurand

Output span (span)The algebraic difference between the lower and uppernominal values of the output signal

Overcurrent re layA protection relay whose tripping decision is related tothe degree by which the measured current exceeds a setvalue.

Overshoot t imeThe overshoot time is the difference between theoperating time of the relay at a specified value of theinput energising quantity and the maximum duration of the value of input energising quantity which, whensuddenly reduced to a specific value below the operating

level, is insufficient to cause operationParametric conjunct ive testA conjunctive test that ascertains the range of values of each parameter for which the test meets specificperformance requirements

PCBPrinted Circuit Board

PCCPoint of Common Coupling

PED

Power Electronic Device

Phase angle t ransducerA transducer used for the measurement of the phaseangle between two a.c. electrical quantities having thesame frequency

Pick-upA relay is said to ‘pick-up’ when it changes from the de-energised position to the energised position

Pi lot channelA means of interconnection between relaying points forthe purpose of protection

PLCProgrammable Logic Controller. A specialised computerfor implementing control sequences using software

PLCCPower Line Carrier Communication

Point of Common Coupl ingThe interface between an in-plant network containing

embedded generation and the utility distributionnetwork to which the in-plant network is connected

POWPoint-on- Wave. Point-on-wave switching is the processto control moment of switching to minimise the effects(inrush currents, overvoltages)

Power Electronic DeviceAn electronic device (e.g. thyristor or IGBT) or assemblyof such devices (e.g. inverter). Typically used in a powertransmission system to provide smooth control of output

of an item of plantPower factorThe factor by which it is necessary to multiply theproduct of the voltage and current to obtain the activepower

Power Line Carr ier Communicat ionA mean of transmitting information over a powertransmission line by using a cariier fraquencysuperimpozed on the normal power frequency.

PPS

Positive Phase SequenceProtected zoneThe portion of a power system protected by a givenprotection system or a part of that protection system

Protect ion equ ipmentThe apparatus, including protection relays, transformersand ancillary equipment, for use in a protection system

Protect ion re layA relay designed to initiate disconnection of a part of anelectrical installation or to operate a warning signal, in

the case of a fault or other abnormal condition in theinstallation. A protection relay may include more thanone electrical element and accessories

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Protect ion scheme

The co-ordinated arrangements for the protection of oneor more elements of a power system. A protectionscheme may comprise several protection systems

Protect ion systemA combination of protection equipment designed tosecure, under predetermined conditions, usually

abnormal, the disconnection of an element of a powersystem, or to give an alarm signal, or both

ProtocolA set of rules that define the method in which a functionis carried out – commonly used in respect of communications links, where it defines the hardware andsoftware features necessary for successfulcommunication between devices.

PSMPlug Setting Multiple – a term used in conjunction with

electromechanical relays, denoting the ratio of the faultcurrent to the current setting of the relay

PSTNPublic Switched Telephone Network

PT100Platinum resistance temperature probe

RResistance

R.M.S .-sens ing t ransducerA transducer specifically designed to respond to the true

r.m.s. value of the input and which is characterised bythe manufacturer for use on a specified range of waveforms

Rat io correct ionA feature of digital/numerical relays that enablescompensation to be carried out for a CT or VT ratio thatis not ideal

RatingThe nominal value of an energising quantity that appearsin the designation of a relay. The nominal value usually

corresponds to the CT and VT secondary ratingsRCDResidual Current Device. A protection device which isactuated by the residual current

RCPRemote Control Point. The Remote Control Point is aSCADA interface. Several RCP’s may be managed withdifferent communication protocols. Physicalconnections are done at a Gateway or at substationcomputers or at a substation HMI

React ive power (var ) t ransducerA transducer used for the measurement of reactiveelectrical power

Rec la im t ime (auto-rec lose)The time between a successful closing operation,measured from the time the auto-reclose relay closingcontact makes until a further reclosing sequence ispermitted in the event of a further fault occurring

REFRestricted Earth Fault

Reference condi t ionsConditions of use for a transducer prescribed forperformance testing, or to ensure valid comparison of results of measurement

Reference rangeA specified range of values of an influence quantitywithin which the transducer complies with therequirements concerning intrinsic errors

Reference va lueA specified single value of an influence quantity at which

the transducer complies with the requirementsconcerning intrinsic errors

RelaySee Protection relay

Reset t ing va lueThe limiting value of the characteristic quantity at whichthe relay returns to its initial position

Res idual currentThe algebraic sum, in a multi-phase system, of all theline currents

Res idual vo l tageThe algebraic sum, in a multi-phase system, of all theline-to-earth voltages

Response t imeThe time from the instant of application of a specifiedchange of the measurand until the output signal reachesand remains at its final steady value or within a specifiedband centred on this value

Revers ib le output currentAn output current which reverses polarity in response to

a change of sign or direction of the measurandRipple content of the outputWith steady-state input conditions, the peak-to-peakvalue of the fluctuating component of the output

r .m.s .Root Mean Square

RMURing Main Unit

ROCOFRate Of Change Of Frequency (protection relay)

RSVCRelocatable Static Var Compensator

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RTDResistance Temperature Detector

RTOSReal Time Operating System

RTURemote Terminal Unit. An IED used specifically forinterfacing between a computer and other devices.

Sometimes may include control/monitoring/storagefunctions

SATSite Acceptance Test. Validation procedures forequipment executed with the customer on site

SCADASupervisory Control and Data Acquisition

SCLSubstation Configuration Language. Normalisedconfiguration language for substation modelling (as

expected by IEC 61850-6)

SCPSubstation Control Point. HMI computers at substationlevel allowing the operators to control the substation

SCSSubstation Control System

Sett ingThe limiting value of a ‘characteristic’ or ‘energising’quantity at which the relay is designed to operate underspecified conditions. Such values are usually marked on

the relay and may be expressed as direct values,percentages of rated values, or multiples

SFCSequential Function Chart: One of the IEC 61131-3programming languages

Short-term stabi l i tyThe stability over a period of 24 hours

Simplex communicat ions systemA communications system in which data can only travelin one direction

Single-shot rec los ingAn auto-reclose sequence that provides only onereclosing operation, lock-out of the CB occurring if itsubsequently trips

S. I .R .System Impedance Ratio

Single e lement t ransducerA transducer having one measuring element

SOE

Sequence Of EventsSOTFSwitch on to Fault (protection)

Spec i f i c con junct ive testA conjunctive test using specific values of each of theparameters

Spr ing winding t imeFor spring-closed CB’s, the time for the spring to be fullycharged after a closing operation

ST

Structured Text: One of the IEC 61131-3 programminglanguages

Stabi l i ty (of a t ransducer)The ability of a transducer to keep its performancecharacteristics unchanged during a specified time, allconditions remaining constant

Stabi l i ty (of a protect ion system)The quantity whereby a protection system remainsinoperative under all conditions other than those forwhich it is specifically designed to operate

Stabi l i ty l imit s (of a protect ion system)The r.m.s. value of the symmetrical component of thethrough fault current up to which the protection systemremains stable

Start ing re layA unit relay which responds to abnormal conditions andinitiates the operation of other elements of theprotection system

STATCOMA particular type of Static Var Compensator, in which

Power Electronic Devices such as GTO’s are used togenerate the reactive power required, rather thancapacitors and inductors

Stat ic re layAn electrical relay in which the designed response isdeveloped by electronic, magnetic, optical or othercomponents without mechanical motion. Excludesrelays using digital/numeric technology

Stat ic Var CompensatorA device that supplies or consumes reactive power,comprised solely of static equipment. It is shunt-connected on transmission lines to provide reactivepower compensation

STCShort Time Current (rating of a CT)

Storage condi t ionsThe conditions, defined by means of ranges of theinfluence quantities, such as temperature, or any specialconditions, within which the transducer may be stored(non-operating) without damage

SVCStatic Var Compensator

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System di sturbance t ime (auto-rec lose)The time between fault inception and CB contactsmaking on successful re-closure

System impedance rat ioThe ratio of the power system source impedance to theimpedance of the protected zone

T101

Term used for IEC 60870-5-101 protocol

Tap changerA mechanism, usually fitted to the primary winding of atransformer, to alter the turns ratio of the transformer bysmall discrete amounts over a defined range

TCP/ IPTransmission Control Protocol/Internet Protocol. Acommon protocol for the transmission of messages overthe Internet

TCS

Trip Circuit Supervision

TC57Technical Committee 57 working for the IEC andresponsible for producing standards in the field of Protection (e.g. IEC 61850)

TFa) Transfer Function of a device (usually an element of acontrol system

b) Transient Factor (of a CT)

Through fau l t currentThe current flowing through a protected zone to a faultbeyond that zone

Time delayA delay intentionally introduced into the operation of arelay system

Time delay re layA relay having an intentional delaying device

TPITap Position Indicator (for transformers)

Transducer ( e l ec t r i ca l measu r ingt ransducer)A device that provides a d.c. output quantity having adefinite relationship to the a.c. measurand

Transducer wi th of f set zero ( l i ve zero)A transducer which gives a predetermined output otherthan zero when the measurand is zero

Transducer wi th suppressed zeroA transducer whose output is zero when the measurandis less than a certain value

Unit e lect r i ca l re layA single relay that can be used alone or in combinationswith others

Unit protect ionA protection system that is designed to operate only forabnormal conditions within a clearly defined zone of thepower system

Unrest r i c ted protect ionA protection system which has no clearly defined zone of operation and which achieves selective operation only by

time gradingUCAUtility Communications Architecture

UPSUninterruptible Power Supply

UTCUniversal Time Coordinates

V Voltage

VCB Vacuum Circuit Breaker

VDEWTerm used for IEC 60870-5-103 protocol. The VDEWprotocol is a subset of the IEC 60870-5-103 protocol

Vector group compensat ionA feature of digital and numerical relays thatcompensates for the phase angle shift that occurs intransformers (including VT’s) due to use of dissimilarwinding connections – e.g. transformers connecteddelta/star

Voltage trans ducerA transducer used for the measurement of a.c. voltage

VT Voltage Transformer

XReactance

ZImpedance • A1 •

A p p e n d i x 1 -


N t k P t t i & A t t i G i d • 4 6 5 •

Appendix 1-454-465

Documents

Transcript of Appendix 1-454-465