浙大研修班(仅供参考学习)1

SwitchingTransient周铮ManitobaHVDCResearchCentreJuly2008PSCADSeminarChinaJuly20081TransientOverVoltages-TOVDuetoswitchingactions-Lineenergizing-Capacitorbankswitching-Breakerre-strike-Transformerenergizing-Faultclearance2PSCADSeminarChinaJuly20080.0000.0200.0400.0600.0800.1000.1200.140.........-10.010.0Eap-400600Eas0.0000.0500.1000.1500.2000.2500.300ENERGY(kJ/kV)-0.4500.050ImovTransientOverVoltagestudies-TOV-Duetoswitchingactions-Re-distributionofstoredenergyinL-Celements-Insulationfailureofequipment-Switchinginstanthasanimpactonthemagnitude-Dampingduetoloadsandlosses-UseofMOV(Surgearrester)tosuppressstress0.003[H]#1#20.100[MVA].415[kV]/11[kV]BRK400[ohm]0.0005[H]0.07[ohm]320[uF]20[uF]11kVSystemBusUtilityCapbanksforvoltagesupportL1C1L2C2L1.C1==L2.C23PSCADSeminarChinaJuly2008-LineenergizingRRLTlineTLineTBRKEaEsaEraTlineBRKL#1#2500kVline450km500kVBus30[m]10[m]C1C2C3Conductors:chukarTower:3H50[m]5[m]Voltages0.000.100.200.300.400.50.........-600-400-2000200400600800kVEaEsaEra4PSCADSeminarChinaJuly2008-TransformerEnergizing•Transformerinrushcurrentincludessignificantmagnitudesofharmonicsofthefundamentalfrequency(i.e.,2nd,3rd,4th,5th,etc.).•Thehighestmagnitudestendtooccurforthelowestorderharmonics.•Ifthesystemequivalentimpedanceatoneormoreofthosefrequenciesishigh,thenthevoltageatthepointwillalsobehigh(V=IZ).Thistendstohappenwhenashuntpowercapacitorbankisapplied,causingaparallelresonancewiththesystem.Theproblemexhibitsitselfintheformofalong-termovervoltage,whichhasahighharmoniccontent,lastingformanycycles-evenseconds.PSCADSeminarChinaJuly20085PSCADSeminarChinaJuly20086-0.200-0.150-0.100-0.0500.0000.0500.1000.1500.2000.250yIaTransientOverVoltages-TOV-Capacitorbankre-strike(whenopeningthebreaker)RRLBRKBRK0.1[H]1.0[uF]0.1[H]1.0[uF]OpenCapbank:Graphs0.1700.1800.1900.2000.2100.2200.2300.240.........-400-300-200-1000100200300yVbusEcap-25.0-20.0-15.0-10.0-5.00.05.010.015.020.0yIcap7PSCADSeminarChinaJuly2008SomepointsonCircuitbreakeroperation•Re-strike-TRVRRLBRK10.001[H]3BRK#1#2TLine1TEaEb#1#2OpenMain:Graphs0.19500.20000.20500.21000.21500.22000.2250.........-300-200-1000100200300yEtrv8PSCADSeminarChinaJuly2008SomepointsonCircuitbreakeroperation•Re-strike-TRV•Currentchopping–Breakingsmallinductivecurrents•Prestrike•Singlepoleoperation•Preinsertionresistors•CapacitorBanks–Inrush/outrushcurrents–InterruptingcapacitorbanksRRLBRKBRK0.1[H]1.0[uF]0.1[H]1.0[uF]close9PSCADSeminarChinaJuly2008TheCapacitorEnergizingTransient•Thevoltageacrossacapacitorcannotchangeinstantaneously:•Thestepchangeinvoltagewhenacapacitorisenergizedresultsinanoscillationbetweenthecapacitorandthesysteminductance.•TypicalMagnitude:1.2-1.7per-unitTypicalFrequency:250-1000HzStandardC37.012,C37.06,TP-133-0PSCADSeminarChinaJuly200810CapacitorInrushCurrent•Energizingofacapacitorbankresultsinatransientinrushcurrent.•Magnitudeandfrequencyofinrushcurrentisafunctionof:•Appliedvoltage•Sourceinductance•Bankcapacitance•Inrushreactor(orpreinsertionreactorsize)•Breaker(switch)inrushcapability,Ipkandfshouldbeevaluated.PSCADSeminarChinaJuly20081112IIiscpkCLisf/21Ipk20I1fi=1kHzBack-to-BackCapacitorSwitching•Energizingashuntcapacitorbank,withanadjacentbankalreadyinservice,canresultinhigh-magnitude,high-frequencyinrushcurrents.•Thisoperationisknownas“back-to-backswitching”.•Reactorsorpreinsertiondevicesmayberequiredtolimittheinrushcurrentduringenergizationofthesecondbank.•Breaker(switch)inrushcapability,Ipkandfshouldbeevaluated.PSCADSeminarChinaJuly200812Ipk=severalkAf=2-5kHzBack-to-BackCapacitorSwitching-continuedPSCADSeminarChinaJuly200813where:Voistheinitialvoltageonbanknumber1LbisthebusinductancebetweenbanksLcistheselfinductanceofthecapacitorbanksC1isthecapacitanceofthefirstbankC2isthecapacitanceofthesecondbankCapacitorOutrushCurrent•Outrushcurrentfromacapacitorbankintoanearbyfaultcanbeaconcern.•Thecloseandlatchratingofthecircuitbreakeristheimportantfactor.•Generalpurposebreakers:•Ipk50kA•Ipk*f2x10powerof7•Ipk*fproductisindependentofcapacitorsize(standardforeachvoltagelevel.)PSCADSeminarChinaJuly200814CapacitorOutrushCurrent-continuedPSCADSeminarChinaJuly200815CapacitorEnergizingOvervoltageControlMethods•Uncontrolled•Nopreventativemeansapplied(alwayssimulationbasecaseforcomparisonofeffectivenessofothermethods).•Synchronousclosingcontrol•Methodforcontrollingovervoltagebyswitchingwhenthevoltageacrosstheswitchattheclosinginstantisequaltozero(zerovoltageoncapacitor-zerovoltageonbus).•Pre-insertiondevice•Methodforcontrollingovervoltagebyinsertinganimpedance(usuallyinductanceorresistance)inserieswiththecomponenttobeenergizedvoltage.•Arresters•Methodforcontrollingovervoltageby“clipping”ataspecifiedprotectivelevel.PSCADSeminarChinaJuly200816Prestrike/RestrikeTransients•Prestrikingoccursduringswitchclosing-highfrequencyinrushcurrentisinterruptedasthecontactsclose.•Restrikingoccursduringswitchopening-highfrequencyinrushcurrent(andtransientovervoltages)occurwhentherecoveryvoltageexceedsthedielectricstrengthoftheswitch.•Theworstcaserestrikeoccursapproximatelyone-halfcycleaftercurre