protection course - chapter 1

8/10/2019 protection course - chapter 1

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POWER SYSTEM PROTECTIONPOWER SYSTEM PROTECTION

Prof. Masoud & ShehabProf. Masoud & Shehab

CC00NTINOUES COURSENTINOUES COURSE

TOTAL MARKSTOTAL MARKS 200200

22ndnd MTMT 2020

LAB.LAB. 2020 FINAL EXAMFINAL EXAM 120120


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Course ContentsCourse Contents 1 One

INTRODUCTION TO PROTECTIVE RELAYING

2 TwoPOWER SYSTEM RELAYING PRINCIPLES

3 Three

urren an o age rans ormers 4 FourNon-Pilot Over Current and DistanceProtection Of

Transmission Lines 55 FiveFive

BASIC ELEMENTS OF DIGITAL PROTECTION


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11 ONEONE

INTRODUCTION TOINTRODUCTION TOPROTECTIVE RELAYINGPROTECTIVE RELAYING

What is relaying,

,

Power system bus configurations ,

The nature of relaying,

Abnormalities, Selectivity and Zones of protection,

Relay speed,


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11 ONEONE

INTRODUCTION TO PROTECTIVEINTRODUCTION TO PROTECTIVERELAYINGRELAYING

Primary and back up protection,

Single and three phase tripping and reclosing,

Elements of protection system,


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WHAT IS RELAYING ?WHAT IS RELAYING ? RelayingRelaying isis thethe branchbranch ofof electricelectric powerpower

engineeringengineering concernedconcerned withwith thetheprinciplesprinciples ofof designdesign andand operationoperation ofof

'' '''protective'protective relays')relays') whichwhich detectdetectabnormalabnormal powerpower systemsystem conditions,conditions,

andand initiateinitiate correctivecorrective actionaction asas quicklyquicklyasas possiblepossible inin orderorder toto returnreturn thethe powerpowersystemsystem toto itsits normalnormal statestate..


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11..11 WHAT IS RELAYING ?WHAT IS RELAYING ?

TheThe functionsfunctions ofof thethe systemsystemprotectionprotection andand coordinationcoordination areare::

systemsystem..

ToTo limitlimit thethe extentextent andand durationdurationofof serviceservice interruptioninterruption..


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MULTIMULTI--LAYERED STRUCTURELAYERED STRUCTURE

OF POWER SYSTEMSOF POWER SYSTEMS


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11..33 POWER SYSTEM BUSPOWER SYSTEM BUS

CONFIGURATIONSCONFIGURATIONS

Operating Voltage LevelsOperating Voltage Levels A radial power systemA radial power system

A network power systemA network power system


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Operating Voltage LevelsOperating Voltage Levels


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REDIAL POWER SYSTEMREDIAL POWER SYSTEM


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A Network Power SystemA Network Power System


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(a) single bus,(a) single bus,single breaker;single breaker;

Substation Bus ArrangementsSubstation Bus Arrangements

(b) two bus, one(b) two bus, onebreaker;breaker;(c) two bus,(c) two bus,two breaker;two breaker;

(d) ring bus;(d) ring bus;(e) breaker(e) breaker--andand--aa--halfhalf


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Power System DesignPower System Design

RequirementsRequirements

11.. QuicklyQuickly isolateisolate thethe effectedeffectedportionportion..

22.. MinimizeMinimize thethe magnitudemagnitude ofof thetheavailableavailable shortshort circuitcircuit currentcurrent..

33.. ProvideProvide alternatealternate circuitscircuits


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APPLICATIONAPPLICATION 11..11


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Protection is provided to achieveProtection is provided to achieve

the following goals:the following goals: Regain the systemsRegain the systems stabilitystability as fast asas fast as

possible after fault occurrence.possible after fault occurrence. Allow continuity of load supply,Allow continuity of load supply,

throu hthrou h

1. fast isolation of faulted parts.

2. providing alternative paths of power

supply to affected loads Keep the electrical devices away fromKeep the electrical devices away fromany damage during fault occurrenceany damage during fault occurrence


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THE NATURE OF RELAYINGTHE NATURE OF RELAYING DetectionDetection

TheThe functionfunction byby whichwhich thethe protectionprotectionsystemsystem feelsfeels thethe faultfault casecase.. SelectionSelection

ItIt representsrepresents selectingselecting ofof ::TheThe faultedfaulted partpart ofof aa powerpower systemsystemTheThe reactionreaction toto suchsuch aa faultfault

OperationOperation ItIt representsrepresents thethe finalfinal decisiondecision ofof thethe

protectionprotection system,system, isis disconnectingdisconnecting thethe

rightright trippingtripping circuitcircuit


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ApplicationApplication


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AbnormalitiesAbnormalities1.1. Over loadOver load

22. Sudden loss of load. Sudden loss of load33. Unbalanced voltage system. Unbalanced voltage system

44. Over voltage. Over voltage55. Under voltage. Under voltage

66. Open conductor. Open conductor


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AbnormalitiesAbnormalities77. Over current due to faults such. Over current due to faults such

as;as;

Single line to groundSingle line to ground

Double line to groundDouble line to ground

Double lineDouble line

Symmetrical fault (three line fault)Symmetrical fault (three line fault)

88. Under frequency. Under frequency Over frequencyOver frequency


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ndnd

..


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Basic Terms Used onBasic Terms Used on

ro ec onro ec on


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RELIABILITYRELIABILITY The need for a high degree of

reliability needs the following:

a. Correct design.

b. Correct installation.

c. Testing and maintenance


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Supply reliability, its Cost andSupply reliability, its Cost and

Value to the consumerValue to the consumer


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Reliability,Reliability, DependabilityDependability, and, and

SecuritySecurity

ReliabilityReliability isis generallygenerally understoodunderstoodtoto measuremeasure thethe degreedegree ofof certaintycertainty

thatthat aa piecepiece ofof equipmentequipment willwillperformperform asas intendedintended..


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Selectivity of Relays and ZonesSelectivity of Relays and Zones

of Protectionof Protection

TheThe propertyproperty ofof securitysecurity ofof relays,relays, thatthat is,is,

thethe requirementrequirement thatthat theythey notnot operateoperate forforfaultsfaults forfor whichwhich theythey areare notnot designeddesigned toto

,,powerpower systemsystem -- calledcalled zoneszones ofof protectionprotection --forfor whichwhich aa givengiven relayrelay oror protectiveprotective systemsystem

isis responsibleresponsible.. TheThe relayrelay willwill bebe consideredconsideredtoto bebe securesecure ifif itit respondsresponds onlyonly toto faultsfaultswithinwithin itsits zonezone ofof protectionprotection..


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CLOSED AND OPEN ZONES OFCLOSED AND OPEN ZONES OF

PROTECTIONPROTECTION


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SELECTIVITYSELECTIVITY Protection is arranged in zones, which

should cover the power systemcompletely, leaving no part

.

protection is required to select and triponly the nearest circuit breakers. This

property of selective tripping is alsocalled 'discrimination' and is achievedby two general methods:


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ZONES OF PROTECTIONZONES OF PROTECTION Location of current transformers on

both sides of the circuit breaker

.


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ZONES OF PROTECTIONZONES OF PROTECTION

Location of current transformers oncircuit side of the circuit breaker.


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Overlapping Zones of ProtectionOverlapping Zones of Protection

SystemsSystems


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Zone overlap with different typesZone overlap with different types

of CTs and circuit breakersof CTs and circuit breakers


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rdrd


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STABILITYSTABILITY

ThisThis term,term, appliedapplied toto protectionprotection asasdistinctdistinct fromfrom powerpower networks,networks,refersrefers toto thethe abilitabilit ofof thethe s stems stem

toto remainremain inertinert toto allall loadloadconditionsconditions andand faultsfaults externalexternal toto

thethe relevantrelevant zonezone..


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SPEEDSPEED


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SPEEDSPEED ((11)) InstantaneousInstantaneous:: TheseThese relaysrelays

operateoperate asas soonsoon asas aa securesecure decisiondecision isismademade.. NoNo intentionalintentional timetime delaydelay isisin rin r l wl w wnwn hh r lr l

responseresponse.. ((22)) TimeTime--DelayDelay:: AnAn intentionalintentional timetime

delaydelay isis insertedinserted betweenbetween thethe relayrelaydecisiondecision timetime andand thethe initiationinitiation ofof thethetriptrip actionaction..


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SPEEDSPEED ((33)) highhigh--SpeedSpeed::AA relayrelay thatthat operatesoperates

inin lessless thanthan aa specifiedspecified limelime.. TheThespecifiedspecified timetime inin presentpresent practicepractice isis 5050milli nmilli n ll nn nn HzHz

system)system).. ((44)) UltraUltra HighHigh --SpeedSpeed:: ThisThis termterm isis

notnot includedincluded inin thethe RelayRelay StandardsStandardsbutbut isis commonlycommonly consideredconsidered toto bebeoperationoperation inin 44 millisecondsmilliseconds oror lossloss..


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SENSITIVITYSENSITIVITY Sensitivity is a term frequently

used when referring to theminimum operating current of a

comp ete protect ve system.protective system is said to besensitive if the primary operating

current is low.

PRIMARY AND BACK UPPRIMARY AND BACK UP


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PRIMARY AND BACK UPPRIMARY AND BACK UP

PROTECTIONPROTECTION Many factors may cause protection

failure and there is always somepossibility of a circuit breaker failure.

,

supplement primary protection withother systems to 'back-up' theoperation of the main system and tominimize the possibility of failure toclear a fault from the system.

APPLICATION lAPPLICATION l 44


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APPLICATION l.APPLICATION l.44Duplicate primary, local backup andDuplicate primary, local backup and

remote backup protectionremote backup protection

Single and Three phase TrippingSingle and Three phase Tripping


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and Reclosingand Reclosing TheThe prevailingprevailing practicepractice inin thethe UnitedUnited StatesStates

isis toto triptrip allall threethree phasesphases ofof thethe faultedfaultedpowerpower systemsystem elementelement forfor allall typestypes ofof faultsfaults..InIn severalseveral EuropeanEuropean andand otherother countries,countries, ititss aa commoncommon prac ceprac ce oo r pr p on yon y ee au eau e

phasephase forfor aa phasephase--toto--groundground fault,fault, andand tototriptrip allall throethroe phasesphases forfor allall multimulti--phasephasefaultsfaults onon transmissiontransmission lineslines.. ThoseThosedifferencesdifferences inin thethe trippingtripping practicepractice areare thetheresultresult ofof severalseveral fundamentalfundamental differencesdifferences ininthethe designdesign andand operationoperation ofof powerpower systemssystems



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and Reclosingand Reclosing

AllAll reclosingreclosing operationsoperations shouldshould bebesupervisedsupervised (i(i..ee.. controlled)controlled) bybya ro riatea ro riate interlocksinterlocks toto reventrevent

anan unsafe,unsafe, damaging,damaging, ororundesirableundesirable reclosingreclosing operationoperation..

SomeSome ofof thethe commoncommon interlocksinterlocks forforreclosingreclosing areare::



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and Reclosingand Reclosing ((11)) VoltageVoltage CheckCheck:: UsedUsed whenwhen goodgood operatingoperating

practicepractice demandsdemands thatthat aa certaincertain piecepiece ofofequipmentequipment bebe energizedenergized fromfrom aa specificspecific sideside..

ForFor example,example, itit maymay hehe desirabledesirable toto alwaysalways

energizeenergize aa transformertransformer fromfrom itsits highhigh voltagevoltagesideside.. ThusThus ifif aa reclosingreclosing operationoperation isis likelylikely totoenergizeenergize thatthat transformer,transformer, itit wouldwould bebe wellwell toto

checkcheck thatthat thethe circuitcircuit breakerbreaker onon thethe lowlow voltagevoltagesideside isis closedclosed onlyonly ifif thethe transformertransformer isis alreadyalreadyenergizedenergized..



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and Reclosingand Reclosing ((22)) SynchronizingSynchronizing Check Check:: ThisThis checkcheck maymay bebe

usedused whenwhen thethe reclosingreclosing operationoperation isis likelylikely totoenergizeenergize aa piecepiece ofof equipmentequipment fromfrom bothboth sidessides.. InInsuchsuch aa case,case, itit maymay bebe desirabledesirable toto checkcheck thatthat thethewowo sourcessources w cw c wouwou ee connec econnec e yy ee

reclosingreclosing breakerbreaker areare inin synchronismsynchronism andandapproximatelyapproximately inin phasephase withwith eacheach otherother.. IfIf thethe twotwosystemssystems areare alreadyalready inin synchronism,synchronism, itit wouldwould bebe

sufficientsufficient toto checkcheck thatthat thethe phasephase angleangle differencedifferencebetweenbetween thethe twotwo sourcessources isis withinwithin certaincertainspecifiedspecified limitslimits..



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and Reclosingand Reclosing IfIf thethe twotwo systemssystems areare likelylikely toto bebe unun--

synchronized,synchronized, andand thethe closingclosing ofof thethecircuitcircuit breakerbreaker isis goinggoing lolo synchronizesynchronize

,,

monitormonitor thethe phasorsphasors ofof thethe voltagesvoltages ononthethe twotwo sidessides ofof thethe reclosingreclosing circuitcircuitbreakerbreaker andand closeclose thethe breakerbreaker asas thethephasorsphasors approachapproach eacheach otherother..



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and Reclosingand Reclosing ((33)) EquipmentEquipment Check Check:: ThisThis checkcheck isis toto

ensureensure thatthat somesome piecepiece ofof equipmentequipment isis notnotenergizedenergized accidentallyaccidentally..

TheseThese interlocksinterlocks cancan bebe usedused eithereither inin thethe

manualmanual oror inin thethe automaticautomatic modemode.. itit isis thethepracticepractice ofof somesome utilities,utilities, however,however, notnot totoinhibitinhibit thethe manualmanual reclosereclose operationoperation ofof

circuitcircuit breakersbreakers onon thethe assumptionassumption thatthat thetheoperatoroperator willwill makemake thethe necessarynecessary checkschecksbeforebefore hehe reclosesrecloses thethe circuitcircuit breakerbreaker..



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and Reclosingand Reclosing InIn extremeextreme situations,situations, sometimessometimes thethe

onlyonly wayway toto restorerestore aa powerpower systemsystem isisthroughthrough operatoroperator intervention,intervention, andandautomaticautomatic interlocksinterlocks maymay preventprevent oror

delaydelay thethe restorationrestoration operationoperation.. OnOn thetheotherother hand,hand, ifif leftleft toto thethe operatoroperator duringduringmanualmanual operation,operation, therethere isis thethe

possibilitypossibility thatthat thethe operatoroperator maymay notnotmakemake thethe necessarynecessary checkschecks beforebeforereclosingreclosing..


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Automatic ReclosingAutomatic Reclosing

AutomaticAutomatic reclosingreclosing cancan bebe highhigh speed,speed, oror ititmaymay bebe delayeddelayed.. TheThe termterm highhigh speedspeedgenerallygenerally impliesimplies reclosingreclosing inin timestimes shortershorterthanthan 11 secondsecond.. ManyMany utilitiesutilities maymay initiateinitiate

(such(such asas groundground faults),faults), andand notnot forfor othersothers..DelayedDelayed reclosingreclosing usuallyusually operatesoperates inin severalseveralsecondsseconds oror eveneven inin minutesminutes.. TheThe timingtiming forforthethe delayeddelayed reclosingreclosing isis determineddetermined bybyspecificspecific conditionsconditions forfor whichwhich thethe delaydelay isisintroducedintroduced..

1515KV &KV & 2727KV Automatic CircuitKV Automatic Circuit


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ReclosersReclosers


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AutorecloserAutorecloser

andandInstallationInstallation


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B tt d DC S lB tt d DC S l


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Battery and DC SupplyBattery and DC Supply

SinceSince thethe primaryprimary functionfunction ofof aa protectionprotectionsystemsystem isis toto removeremove aa fault,fault, thethe abilityability toto triptrip

aa circuitcircuit breakerbreaker throughthrough aa relayrelay mustmust notnot bebecompromisedcompromised duringduring aa fault,fault, whenwhen thethe acacvoltagevoltage availableavailable inin thethe substationsubstation maymay notnot

.. ,,

closeclose--inin threethree phasephase faultfault cancan resultresult inin zerozeroacac voltagevoltage atat thethe substationsubstation acac outletsoutlets..TrippingTripping power,power, asas wellwell asas thethe powerpowerrequiredrequired byby thethe relays,relays, cannotcannot thereforetherefore bebeobtainedobtained fromfrom thethe acac system,system, andand isis usuallyusuallyprovidedprovided byby thethe stationstation batterybattery..

Circuit BreakersCircuit Breakers examexam


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Circuit BreakersCircuit Breakers examexam TheThe circuitcircuit breakerbreaker isolatesisolates thethe faultfault byby

interruptinginterrupting thethe currentcurrent atat oror --nearnear aa

currentcurrent zerozero.. AtAt thethe presentpresent time,time, anan EHVEHVcircuitcircuit breakerbreaker cancan interruptinterrupt faultfault currentscurrentsofof thethe orderorder ofof 100000100000 amperesamperes atat systemsystemvo tage svo tage s upup toto ..

ItIt cancan dodo thisthis asas quicklyquickly asas thethe firstfirstcurrentcurrent zerozero afterafter thethe initiationinitiation ofof aa fault,fault,

althoughalthough itit moremore oftenoften interruptsinterrupts atat thethesecondsecond oror thirdthird currentcurrent zerozero


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ContactContactarc (a)arc (a)

EquivalentEquivalentcircuit bcircuit b

ContactsContactsand (c)and (c)

WaveformWaveformss


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138138KV OilKV OilCircuitCircuit

BreakersBreakers

(Dead(DeadTank)Tank)


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End of ChEnd of Ch 0101

Zone overlap with different typesZone overlap with different types


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p ypp yp

of CTs and circuit breakersof CTs and circuit breakers


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LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS


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22 Time delay starting or closing relayTime delay starting or closing relay

33 Checking or interlocking relayChecking or interlocking relay 44 Master contactorMaster contactor

2121 Distance relayDistance relay 2525 Synchronizing or synchronismSynchronizing or synchronism

check relaycheck relay

2727 Undervoltage relayUndervoltage relay



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3030 Annunciator relayAnnunciator relay 3232 Directional power relayDirectional power relay

3737 Undercurrent or under power relayUndercurrent or under power relay 4040 Field failure relayField failure relay

relayrelay 4949 Machine or transformer thermal relayMachine or transformer thermal relay 5050 Instantaneous overcurrent or rate of riseInstantaneous overcurrent or rate of rise

relayrelay 5151 A.c. time overcurrent relayA.c. time overcurrent relay



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5252 A.c. circuit breakerA.c. circuit breaker

5252a Circuit breaker auxiliary switch normallya Circuit breaker auxiliary switch normallyopenopen

22 ww

closedclosed 5555 Power factor relayPower factor relay

5656 Field application relayField application relay

5959 Overvoltage relayOvervoltage relay

6060 Voltage or current balance relayVoltage or current balance relay



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6464 Earth fault protective relayEarth fault protective relay

6767 A.c. directional overcurrent relayA.c. directional overcurrent relay 6868 Blocking relayBlocking relay

7474 Alarm relayAlarm relay 7676 D.c. overcurrent relayD.c. overcurrent relay

7878 Phase angle measuring or outPhase angle measuring or out--ofof--

step protective relaystep protective relay



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7979 A.c. reclosing relayA.c. reclosing relay

8181 Frequency relayFrequency relay 8383 Automatic selective control orAutomatic selective control or

trans er re aytrans er re ay

8585 Carrier or pilot wire receive relayCarrier or pilot wire receive relay

8686 LockingLocking--out relayout relay

8787 Differential protective relayDifferential protective relay

RELAY CONTACT SYSTEMRELAY CONTACT SYSTEM


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RELAY CONTACT SYSTEMRELAY CONTACT SYSTEM

OPERATIONAL INDICATORSOPERATIONAL INDICATORS


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OPERATIONAL INDICATORSOPERATIONAL INDICATORS

As a guide for power system

operation staff, protective systemsare invariably provided with.

In British practice these are called'flags', whereas

in America they are known as'targets'

RELAY TRIPPING CIRCUITSRELAY TRIPPING CIRCUITS


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a. Series sealing.a. Series sealing.

b. Shunt reinforcing.b. Shunt reinforcing.

..

sealing.sealing.



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SUPERVISION OF TRIPSUPERVISION OF TRIP


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CIRCUITSCIRCUITS

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protection course - chapter 1