《电力系统继电保护及应用》课件-中性点非直接接地系统故障分析 -双语

输配电线路的接地保护Groundingprotectionoftransmissionanddistributionline目录页CONTENTSPAGE中性点非直接接地系统故障分析05中性点非直接接地系统接地保护06FaultanalysisofneutralpointnondirectgroundingsystemEarthingprotectionofneutralpointnondirectearthingsystem中性点非直接接地系统故障分析Faultanalysisofneutralpointnondirectgroundingsystem05中性点非直接接地系统故障分析Faultanalysisofneutralpointnondirectgroundingsystem中性点非直接接地系统(小电流接地系统)Indirectgroundingsystemwithneutralpoint(lowcurrentgroundingsystem)中性点不接地Theneutralpointisnotgrounded中性点经消弧线圈接地

Theneutralpointisgroundedthroughthearcsuppressioncoil中性点经电阻接地

Theneutralpointisconnectedtogroundviaaresistor在小接地电流系统中发生单相接地时，一般都允许再继续运行1～2个小时Whenasingle-phasegroundfaultoccursinasmallgroundcurrentsystem,itisgenerallyallowedtocontinuerunningfor1to2hours01对保护的要求Requirementsforprotection要求保护能选出接地线路并及时发出信号12对人身和设备的安全有危险时，应动作于跳闸TheprotectionisrequiredtobeabletoselectthegroundinglineandsendoutasignalintimeWhenthereisadangertothesafetyofpeopleandequipment,trippingshouldbeperformed02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem(a)最简单网络接线示意图(a)Schematicdiagramofthesimplestnetworkwiring(b)A相接地时的网络图(b)NetworkdiagramwhenphaseAisgrounded

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02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem

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各相对地电压为Thevoltageofeachphasetogroundis

(a)最简单网络接线示意图(a)Schematicdiagramofthesimplestnetworkwiring02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem

故障点的零序电压为Thezerosequencevoltageatthefaultpointis

在故障处非故障相中产生的电容电流流向故障点Thecapacitivecurrentgeneratedinthenon-faultphaseatthefaultflowstothefaultpoint

CBA

K(a)最简单网络接线示意图(a)Schematicdiagramofthesimplestnetworkwiring02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem

（b）A相接地时的网络图(b)NetworkdiagramwhenphaseAisgrounded因为全系统A相对地电压均为零，因而各元件A相对地的电容电流也等于零，此时从故障处A相接地点流过的电流是全系统非故障相电容电流之和即IK=IB+IC。由图b可见，其有效值IK=3UφωC0，是正常运行时单相电流的3倍。

BecausethevoltagebetweenphaseAandgroundoftheentiresystemiszero,thephaseAandgroundcapacitivecurrentofeachcomponentisalsoequaltozero.Atthistime,thecurrentflowingfromthefaultyphaseAgroundpointisthesumofthenon-faultyphasecapacitancecurrentsoftheentiresystem,thatis,IK=IB+IC.ItcanbeseenfromFigurebthatitseffectivevalueIK=3UφωC0isthreetimesthesingle-phasecurrentduringnormaloperation.02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem单相接地时，用三相系统表示的电容电流分布图线路I线路IIC0IC0IIC0GGABCCCapacitivecurrentdistributiondiagramrepresentedbyathree-phasesystemwhenasinglephaseisgrounded02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem

当网络中有发电机G和多条线路存在时，如图C所示：WhentherearegeneratorGandmultiplelinesinthenetwork,asshowninFigureC:

02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem非故障线路I的零序电流为线路1本身的电容电流，电容性无功功率的方向由母线指向线路。同理，该结论可适用于电网中线路很多时，每一条非故障的线路。

Uφ-相电压的有效值Uφ-effectivevalueofphasevoltageC0I-线路I的电容值C0I

-capacitancevalueoflineI即非故障线路特点Thatis,non-faultylinecharacteristics其有效值为Itsvalidvaluesare

“”

Thezerosequencecurrentofnon-faultylineIisthecapacitivecurrentofline1itself,andthedirectionofcapacitivereactivepowerisfromthebusbartotheline.Inthesameway,thisconclusioncanbeappliedtoeverynon-faultylinewhentherearemanylinesinthepowergrid.02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem

02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem即零序电流为发电机本身的电容电流，其电容性无功功率的方向是由母线指向发电机，这个特点与非故障线路是一样的。

“”Thatis,thezerosequencecurrentisthecapacitivecurrentofthegeneratoritself,andthedirectionofitscapacitivereactivepowerisfromthebusbartothegenerator.Thisfeatureisthesameasthatofnon-faultylines.单相接地时，用三相系统表示的电容电流分布图线路I线路IIC0IC0IIC0GGABCCCapacitivecurrentdistributiondiagramrepresentedbyathree-phasesystemwhenasinglephaseisgrounded02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem式中C0Σ-全系统每相对地电容的总和Intheformula,C0Σ-thesumofthecapacitanceofeachphaseinthewholesystem

有效值为Thevalidvaluesare

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02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem有效值为Thevalidvaluesare

故障线路中的零序电流，数值等于全系统非故障元件对地电容电流的总和（但不包括故障线路本身）””故障线路的特点是Thecharacteristicsofthefaultylineare

其电容性无功功率的方向由线路指向母线，与非故障线路相反。Thezero-sequencecurrentinafaultylineisequaltothesumofthecapacitancecurrentsofnon-faultycomponentsintheentiresystemtoground(butitdoesnotincludethefaultylineitself)Thedirectionofitscapacitivereactivepowerisfromthelinetothebusbar,whichisoppositetothatofthenon-faultyline.02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem单相接地时，用三相系统表示的电容电流分布图线路I线路IIC0IC0IIC0GGABCCCapacitivecurrentdistributiondiagramrepresentedbyathree-phasesystemwhenasinglephaseisgrounded02中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem（e）单相接地时相量图(e)Phasordiagramwhensinglephaseisgrounded(d）单相接地时，零序等效网络图、(d)Networkdiagramwhensinglephaseisgrounded,zerosequenceequivalent

GC0G

C0ⅠⅠⅡ

C0Ⅱ0

32102中性点不接地系统发生单相接地故障的特点Thecharacteristicofsinglephasegroundingfaultinneutralungroundedsystem结论Conclusion发生单相接地时，全系统都会出现零序电压。Whenasingle-phasegroundfaultoccurs,zerosequencevoltagewillappearintheentiresystem.在非故障线路上有零序电流，其数值等于该线路本身的电容电流，方向为从母线流向线路。Thereisazero-sequencecurrentonanon-faultyline,itsvalueisequaltothecapacitivecurrentofthelineitself,andthedirectionisfromthebusbartotheline.在故障线路上，零序电流为全系统非故障元件对地电容电流之总和，方向为从线路流向母线。Thereisazero-sequencecurrentonanon-faultyline,itsvalueisequaltothecapacitivecurrentofthelineitself,andthedirectionisfromthebusbartotheline.中性点非直接接地系统接地保护Earthingprotectionofneutralpointnondirectearthingsystem0601零序电压保护（绝缘监视装置）Zerosequencevoltageprotection(insulationmonitoringdevice)绝缘监视装置是利用单相接地时出现的零序电压，带延时动作于信号Theinsulationmonitoringdeviceusesthezerosequencevoltagethatoccurswhenasinglephaseisgrounded,andoperatesonthesignalwithadelay该保护只能监测出接地故障，但不能判别出是哪条线路的接地。为了找出故障线路，还需要由运行人员依次短时断开各条线路，再以自动重合闸纠正当断开某条线路时，零序电压信号消失，即说明该线路单相接地。VVVNUVW3U0U>KVUVWThisprotectioncanonlydetectgroundfaults,butcannotidentifywhichlineisgrounded.Inordertofindthefaultyline,theoperatorneedstodisconnecteachlineinturnforashorttime,andthenuseautomaticreclosingtocorrectit.Whenacertainlineisdisconnected,thezerosequencevoltagesignaldisappears,whichmeansthatthelineissingle-phasegrounded.02零序电流保护Zerosequencecurrentprotection利用故障线路的零序电流比非故障线路零序电流大的特点来实现选择性的保护。零序电流保护Zerosequencecurrentprotection为了保证动作的选择性，零序电流保护的动作电流Iset应大于本线路的电容电流，即Selectiveprotectionisachievedbyutilizingthecharacteristicthatthezero-sequencecurrentoffaultylinesislargerthanthatofnon-faultylines.Inordertoensuretheselectivityofoperation,theoperatingcurrentIsetofthezero-sequencecurrentprotectionshouldbegreaterthanthecapacitivecurrentofthisline,thatis02零序电流保护Zerosequencecurrentprotection式中C∑为同一电压等级电网中，各元件每相对地电容之和;灵敏度校验，由于流经故障线路上的零序电流为全网络中非故障线路电容电流的总和，灵敏系数为零序电流保护ZerosequencecurrentprotectionSensitivitycaliberation,sincethezero-sequencecurrentflowingthroughthefaultylineisthesumofthecapacitancecurrentsofthenon-faultylinesintheentirenetwork,thesensitivitycoefficientisIntheformula,C∑isthesumofthecapacitancesofeachcomponentperphaseinthepowergridofthesamevoltagelevel;校验时应采用系统最小运行方式时的电容电流，即C∑为最小时的电容电流。Thecapacitor