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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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APPLICATIONAPPLICATION 11..22
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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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APPLICATIONAPPLICATION 11..33
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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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Single and Three phase TrippingSingle and Three phase Tripping
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
Single and Three phase TrippingSingle and Three phase Tripping
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Single and Three phase TrippingSingle and Three phase Tripping
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::
Single and Three phase TrippingSingle and Three phase Tripping
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Single and Three phase TrippingSingle and Three phase Tripping
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..
Single and Three phase TrippingSingle and Three phase Tripping
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Single and Three phase TrippingSingle and Three phase Tripping
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..
Single and Three phase TrippingSingle and Three phase Tripping
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Single and Three phase TrippingSingle and Three phase Tripping
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..
Single and Three phase TrippingSingle and Three phase Tripping
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Single and Three phase TrippingSingle and Three phase Tripping
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..
Single and Three phase TrippingSingle and Three phase Tripping
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Single and Three phase TrippingSingle and Three phase Tripping
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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LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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
LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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
LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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
LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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
LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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LIST OF DEVICE NUMBERSLIST OF DEVICE NUMBERS
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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RELAY TRIPPING CIRCUITSRELAY TRIPPING CIRCUITS
a. Series sealing.a. Series sealing.
b. Shunt reinforcing.b. Shunt reinforcing.
..
sealing.sealing.
RELAY TRIPPING CIRCUITSRELAY TRIPPING CIRCUITS
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RELAY TRIPPING CIRCUITSRELAY TRIPPING CIRCUITS
SUPERVISION OF TRIPSUPERVISION OF TRIP
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CIRCUITSCIRCUITS
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