輸配電線路相間短路的電流保護Currentprotectionforphase-to-phaseshortcircuitsintransmissionanddistributionlines情境五：三段式電流保護整定計算舉例Scenario5:Exampleforthree-stagecurrentprotectionsettingcalculation三段式電流保護整定計算舉例Exampleforthree-stagecurrentprotectionsettingcalculation如圖所示，35kV線路L-1、L-2上均配置有三段式電流保護。已知系統(tǒng)在最大最小運行方式下的系統(tǒng)電抗分別為321G1QF2QF3QFAsshowninthefigure,35kVlinesL-1andL-2areequippedwiththree-stagecurrentprotection.Itisknownthatthesystemreactancesofthesysteminthemaximumandminimumoperatingmodesarerespectively三段式電流保護整定計算舉例Exampleforthree-stagecurrentprotectionsettingcalculation線路L-1、L-2的長度分別為L1=25KM,L2=62KM

；線路每公里正序電抗為X1=0.4Ω；保護2中定時限過電流保護的動作時限為線路L-1的最大負(fù)荷功率為9MW試對線路L-1上配置的三段式電流保護進(jìn)行整定計算。Pleaseperformsettingcalculationofthethree-stagecurrentprotectionconfiguredonlineL-1.電動機自起動系數(shù)Motorself-startingcoefficient

ThelengthsoflinesL-1andL-2areL1=25KMandL2=62KMrespectively;thepositivesequencereactanceperkilometerofthelineisX1=0.4Ω;theoperationtimelimitofthetimelimitovercurrentprotectioninprotection2isThemaximumloadpoweroflineL-1is9MWK1點短路時的三相短路電流Three-phaseshort-circuitcurrentwhenpointK1isshort-circuited最大運行方式下/Inmaximumoperatingmod最小運行方式下

/InminimumoperatingmodeK2點短路時的三相短路電流Three-phaseshort-circuitcurrentwhenK2pointisshort-circuited最大運行方式下/Inmaximumoperatingmod最小運行方式下/Inminimumoperatingmode解：(1)選擇短路點并計算最大、最小短路電流Solution:(1)Selecttheshortcircuitpointandcalculatethemaximumandminimumshortcircuitcurrent對電流保護I段，即瞬時電流速斷保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionI,i.e.theinstantaneouscurrentquick-breakprotection01動作電流Operatingcurrent1對電流保護I段，即瞬時電流速斷保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionI,i.e.theinstantaneouscurrentquick-breakprotection01靈敏度滿足要求Sensitivitymeetsrequirements計算保護范圍、校驗靈敏度2Calculateprotectionrangeandcalibrationsensitivity對電流保護I段，即瞬時電流速斷保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionI,i.e.theinstantaneouscurrentquick-breakprotection01動作電流Operatingcurrent對電流保護II段，即限時電流速斷保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionII,i.e.thetime-limitcurrentquickbreakprotection021動作時限校驗靈敏度對電流保護II段，即限時電流速斷保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionII,i.e.thetime-limitcurrentquickbreakprotection02靈敏度滿足要求23OperationtimelimitCalibrationsensitivitySensitivitymeetsrequirements對電流保護III段，即定時限過電流保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionIII,i.e.thetimelimitovercurrentprotection03動作電流Operatingcurrent1動作時限作為本線路的近后備保護時作為相鄰線路遠(yuǎn)后備保護時對電流保護III段，即定時限過電流保護進(jìn)行整定計算PerformsettingcalculationofthecurrentprotectionsectionIII,i.e.thetimelimitovercurrentprotection032校驗靈敏度3靈敏度滿足要求靈敏度滿足要求/OperationtimelimitCalibrationsensitivityWhenitisusedasnearbackupprotectionforthislineWhenit