Embed Size (px)
Citation preview
“PowerSystemProtection“– WhereAreWeToday?
MelihaB.SelakPowerSystemProtection&Control
IEEEPESDistinguishedLecturerProgramPrecedingIEEEPESVicePresidentforChapters
PESStudentEnergyConference(ZEC2015),Zagreb,Dec10th,2015
1
ElectricalPowerSystemComponents
10-7 10-5 10-3 10-1 101 103 105Lightning
Switching
Sub-synchronous resonance
TransientstabilityLongtermdynamics
Tie-lineregulation
Dailyloadvariation
Timescale (seconds)
HVDC,FACTS, etc.
Generatorcontrol
Protection
Primemovercontrol
LoadFrequencyControl
Operatoractions
1cycle 1sec 1min 1hr 1day
Impulsive transients
Oscillatorytransients
Short-durationvariationsLong-durationvariations
Imbalance,harmonics, inter-harmonics, notching,noise
Voltagefluctuations
Frequencyvariations
Electromagnetictransientmodelingandsimulation
TimeScalesofPowerSystemPhenomena
4
• SteadyStateShortCircuitFaultLevel
ü EquipmentSelection(isolationlevel)ü ReferenceforProtectionSettings
• DynamicStateSimulationSpeedofthefaultclearingtime
ü Non-communicationassistedschemeü Communicationassistedscheme
• TransientsSimulationTrippingPriorityregardingto:
ü Overvoltage'sconditionsü PowerQuality(harmonics)
SystemStudiesandOutputs
PowerSystemTransmission5
ØElectricalBehaviorofTransmissionLine-[dV/dx]=[Z][I]-[dI/dx]=jω[C][V]
ØSeriesimpedancematrix[Z]
[ ] [ ] [ ]
ikik
iiciiii
LjZLjRZ
LjRZ
ω
ω
ωωω
=
+=
+= )()(
HowtoModelTransmissionLine?
( )jba
P
rhL
i
ioii
−=⎟⎟
⎠
⎞
⎜⎜
⎝
⎛ +⋅⎟⎟
⎠
⎞
⎜⎜
⎝
⎛=
2ln
2πµ
jdcdDL
ik
ikoik
−=⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛=
'
ln2πµ
ωµρj o
oP =
TransmissionLineInductance
.)(,)()(Z
,2
ii
'
ikikik
iiii
c
ii
c
ii
o
o
ik
ik
i
i
cii
LRcjdjdcjZLjRajbRjbajR
Ddrhf
fR
+=+=−=
+=++=−+=
=
=
=
=
=
=
=
=
=
ωωω
ωωωωµ
ρ
πω
a.c.resistanceofconductori,
angularfrequency,
frequencyinHz,
averageheightabovegroundofconductori,
radiusofconductori,
directdistancebetweenconductorsi andk,
distancebetweenconductori andimage
atcomplexdepthofconductork,
earthresistivity,
earthpermeability.
FormulaQuantities
PowerSystemDisturbancesandFaults
• Inadequatesupplyequipment– Resultofinadequateplanningorunexpectedrapidloaddemand– Exceedingsupplycapabilityresultsinloadlosses
• Manyblackoutscausedbyoperatingsystemstooclosetostabilitylimits
9
PowerSystemProtectionProtectiverelaysprovidethe“brains”tosensetrouble,buttheyarenotabletoopenandisolatetheproblemareaofpowersystem.
#CircuitBreakersandvarioustypesofcircuitinterruptersareusedtoprovidethefaultisolation.
10
RelayingFundamentals11
52
21LTrip
Output
Voltage Transformer
(VT)
Current Transformer
(CT’s)
(Optional)
Relay
Circuit Breaker
AC
Bus
AC Circuit
Protection Duties12
• Protectionsystemorrelaymustdetectthefaultandsignalcircuitbreakertoisolatethefaultreliablyandasfastaspossible.
ProtectionSchemeDesignCriteria
13
Theprotectionsystemsshouldbedependableandsecure
14
Reliability
Reliability
15
Impedancemeasurement
16
SteppedDistance17
• Note:NOTcommunicationsassisted,butgoodbackgroundforotherschemes
Z1aZ1b
Z2a
Z2b
Examplereachesandtimecoordination
18
Time (Cycles)
60
40
20
Sub A Sub B Sub C Gen X
Zone 1
Zone 3
Zone 2
Zone 1
Zone 3
Zone 2
Zone 1
Zone 3
Zone 2
LineProtectionReachesØ Reaches:
ü Zone1shallnotoverreachprotectedline.ü Zone2elementsshallbesetasfaraspossiblewithoutoverreachingremoteinstantaneouselements.
ü Zone3elementsshallbesettocoverlongestremoteline,orasfaraspossiblewithoutriskoftrippingunderemergencyloadconditions
Ø Speed:ü Zone1instantaneousü Zone2timedelayedtocoordinatewithremoteprotection
ü Zone3timedelayedtocoordinatewithremoteprotection
19
Communicationassistedlineprotection?
Ø Speed,speed,speed…Ø Selectivityproblem(ie:isthefaultbetweenthetwoendsoftheline?)
ØAddingcommunicationsallowscooperationbetweenbothlineterminals,whichimprovesspeedbyimprovingselectivity
20
Permissive Overreaching Transfer Trip
21
• Sending Permissive Trip = “fault is in front of me”• Received Permissive Trip + local Zone 2 = local trip
Z1aZ1b
Z2a
Z2b
Protectionconcept• Protectionsareprovidedbyredundantdesignatedprimary
andstandbyprotection,orPYPNandSYPNusing identical ordifferentmanufacturermultifunctionalrelays.
• Each,PYPNandSYPNareconnectedtoseparatecurrenttransformercoresandvoltagetransformerwindings.
• Dependabilityofthesinglecircuitbreakersareprovidedbybreakerfailureprotectionandprimaryandstandbybreakertripcoils
• Lineprotectionusingtelecommunicationsareequippedwithfunctionsthatoperatetoprovidefaultclearingindependentofthetelecomm
•
22
Telecommunication
Telecommunicationisprovidedwithmodernizednetworkinfrastructure(DigitalMicrowaves)which,togetherwithmultifunctionalprotectiondevicesallowoptimizingtheexisting/newpowersystemoperation.
23
AutomaticReclosing
• Automaticsingle-shotreclosingisprovidedforallairinsulatedtransmissionlines.
• Automaticreclosingisnotprovidedforlinesthatareallcable.
24
PowerQuality
Thisprotectionconsistof• Over-frequency,• Underfrequency,• Over-voltage• Under-voltageelements
25
Security
• Securityisachieved(Secureprotectionsystemshouldnotoperatefornormalsystemoperationorwhennotrequiredtooperatetoclearafault)– withappropriateoperatinglevelsforfaultdetectionfunctions(current,voltageandimpedance),
– withselectiveprotectionsystems,– withsupervisionbyvoltage,impedance,load- blindinganddirectionalfunctions.
26
Selectivity
• Selectivityisachieved• (Protectionsystemsremovefromservicetheminimum
numberofsystemelementsnecessarytoclearafault)– withclosedzoneprotection,– withappropriateoperatinglevelsforfaultdetectionfunctions(current,voltageandimpedance),and
– withtimecoordinationoffaultdetectionfunctions.
27
Speed
• Protectionsystemsprovidefaultclearinginaminimumtime,consideringtimedelaysrequiredtoachievesecurityandselectivity.
• Highspeedfaultclearingwithouttimedelayissometimerequired,inwhichcasesecurityandselectivitymuststillbemaintained.
28
Loadability
• Protectionisnotlimittheloadcarryingcapabilityofmajorequipmentsuchastransmissionlines,transformers,circuitbreakers,disconnectswitches
• Loadability requirementsofNERCStandardareappliedfortransmissionlinesandtransformers
29
Specialapplicationissues• SyncCheck• Outofstep(OOS)protection
TheOOSlogicdetermineswhetherapowerswingisstable andü GeneratesthesetpointsofZone6andZone7associatedtoOOSprotectionü Setthe relaylogictoblockdistanceprotection longer thantheOOStripping delay
• Overloadprotection“Summer”and“winter”settingsaccountforthevariationofratedcircuitcapacitywithambienttemperatureandisappliedinthelineprotectiondevices.
ü Local“Summer”/“Winter”settingsare“ENABLE/DISABLE”ontherelay.ü “Summer”/“Winter”settingsareautomaticallyswitchedbytheanalogquantityDDOY
"TimeandDataManagement".ü SettingsautomaticallyswitchtotheSummerOverLoadprotectionsettingonselectedday
dependofregion(i.e.April1)ofeachyearthenswitchbacktotheWintersettinginwinterperiod(i.e.Nov1).
30
RemedialActionSchemes(RAS)RemedialActionSchemes(specialprotectionschemesdesignedtopreventcascadingoutages,unacceptableoperatingperformanceortosupportsystemoperatinglimits)• RASaredesignedtodetectthesystemcondition
thatcancauseü Instabilityü Overloadü Voltagecollapse
• RASInclude– protectionsensingfacilities– armingfacilitiesunderthecontrolofthesystemcontrolcentres– actionsiteswheregenerationshedding– loadshedding– reactiveswitching
31
MultifunctionalRelayDevicesMultifunctionalnumericalrelaysareusedinmajorityprotectionschemes• allowanimplementationofalmostallthefunctionalities
neededtoprotectandcontrolthepowersystemcomponentsmoreefficiently:ü Fundamentalprotections(OverCurrent,OverVoltage,OverFrequency,Distance,
DifferentialProtections)ü BreakerFailureprotection(BFPN)ü Autoreclose (AR)ü Automaticswitchingofprotectionsettingsü Overloadprotectionü Wideareaspecialprotectionschemes(SPS)orremedialactionscheme(RAS)ü SynchronizedPhasorMeasurement
32
Distributionsystemisdesignedtoserveradialload(Powerflowsfromhighervoltagelevelsdowntocustomers)
33
PowerDistributionSystem
DistributionProtection34
• Relaycharacteristicsareplottedonatimecurrentcharacteristic(TCC)diagram.• Nondirectionalprotectionisneededbecauseofradialsystemconfiguration
G GGeneration
Transmission
DistributionLoads
Demand
Traditional one-way supply system
G
Generation
G
Bi-directional supply system
Supply
Generation
Generation
Transmission
Distribution
Loads
Interconnections
PowerSystemDesignToday
Concernsrelatedtothedistributionsystemoperationandplanning
WithDGincreases,DistributionSystemisbecomingmoreliketransmissionsystem:• doubleormultiplefeedcircuitshavingsignificantchangesinoperation
• protectionsystembecomesmorecomplexduetochangesinsystembehaviorandpowerflowundershort-circuitconditionsüProtectionhavetoaccommodatebi-directionalpowerflows
• safetyofpublicandequipmentüasthenetworkwasnotdesignedtoaccommodatelargernumbersofDG
36
Z1
Iph
DGUtility Utility
Z1
Utility Utility
ü ReducedZ1coverage
ImpedanceSettings
Z2
I ph
DGUtility
Utility
Z2
Utility
Utility
ü MustincreaseZ2coveragetodealwithinfeed
ü Consequence: longer reach if IPP is out of service
ImpedanceSettingswithDG
AForkInTheRoad
HV Grounded star connected
ü no overvoltage problems
but, ground relaying desensitization
HV Delta connected (not a source of ground fault current)
ü no ground relay sensitivity problems
but, overvoltage problems
?
DG’s Transformer connection
TransientOvervoltages
ü Problem- non60HzbasisüEMTPanalysis
Overvoltages approaching 3 pu
GroundRelayDesensitization
WhyisGroundRelaySensitivitySoImportant?
üHighsoilresistivityüHighimpedancefaultsduetoimpedanceinfaultpath
Myremark
AlthoughTelecommunication(providedwithmodernizednetworkinfrastructure)which,togetherwithmultifunctionalprotectiondevicesallowoptimizingtheexisting/newpowersystemoperation,theexpertizeinPowerSystemOperationisMAINKEYinprovidingReliablePowerSystemOperation.
42
