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发电机自动并列装置频差调节单元的设计 张悦辉 发电机 自动 并列 装置 调节 单元 设计

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发电机自动并列装置频差调节单元的设计 张悦辉,发电机自动并列装置频差调节单元的设计,张悦辉,发电机,自动,并列,装置,调节,单元,设计

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华北电力大学科技学院毕业设计(论文)任务书所在院系 电 力 系 专业班号 电气化07k7班 学生姓名 张悦辉 指导教师签名 审批人签字 毕业设计(论文)题目 发电机自动并列装置频差调节单元设计2011年 2 月 21 日毕业设计(论文)主要内容1. 总体方案设计。2. 越前鉴别电路设计。3. 区间鉴别电路设计。4. 逻辑判别电路设计。5. 脉冲展宽电路设计。6. 频差过小自动增速电路设计。7. 调频出口电路设计。二、基本要求1. 掌握发电机自动并列方法和自动并列装置的构成原理。掌握电路仿真软件的使用方法。2. 设计的原理电路要在软件仿真平台上调试通过。3. 完成“本科毕业设计规定、规范”要求的其他工作内容。三、设计(论文)进度序号设计项目名称完成时间备注1查阅资料、撰写文献综述、完成开题报告2011.03.113 周2设计内容第 1项2011.04.222 周（含学习仿真软件）含4周动模、金工实验等3设计内容第 2、3 两项2011.04.082 周4设计内容第 4、5 两项2011.05.062 周5设计内容第 6、7 两项2011.05.202 周6完成并提交论文2011.06.032 周（含外文文献翻译）设计(论文)完成时间： 2011年 06月 10日四、参考资料及文献1 李先彬.电力系统自动化M.北京:水利电力出版社，1986.2 商国才.电力系统自动化M.天津:天津大学出版社,1999.3 田建设.电力系统自动装置实验指导书.保定：华北电力大学校内教材，2008. 4 朱传琴，高安芹. 电子技术基础M.北京:中国电力出版社，2005.5 肖景和.集成运算放大器应用精粹M.人民邮电出版社,2006.6 王冠华, 王伊娜编著. Multisim 8电路设计及应用M.北京:国防工业出版社，2006.7 www.21IC.com/集成电路芯片技术资料.华 北 电 力 大 学 科 技 学 院毕 业 设 计（论 文）开 题 报 告学生姓名： 张悦辉 班级： 电气化07K7 所在院系：电力工程系 所在专业：电气工程及其自动化 设计（论文）题目： 发电机自动并列装置频差调节单元的设计指导教师： 田建设 2011年 3 月 24 日毕 业 设 计（论 文）开 题 报 告一、结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写不低于2000字的文献综述。（另附）二、本课题要研究或解决的问题和拟采用的研究手段（途径）：这个课题主要研究的是自动并列装置的频差调节单元，频差调节单元包括频差方向检测和均频执行两部分。频差调节单元的设计主要是设计频差方向检测电路，包括区间鉴别电路的设计、超前鉴别电路的设计、逻辑判别电路的设计、脉冲展宽电路设计、频差过小自动增速电路设计、调频出口电路设计。这些电路是模拟和数字电子器件组成，运用模拟电子技术和数字电子技术知识来研究各个电路的工作原理，进而根据自己的理解设计更加合理的电路。运用仿真软件Multisim对自己设计的电路进行仿真运行，验证自己设计的电路是否正确合理。三、指导教师意见：1 对“文献综述”的评语： 2对学生前期工作情况的评价（包括确定的研究方法、手段是否合理等方面）：指导教师： 年 月 日FirstInternationalPowerandEnergyCoferencePECon2006November28-29,2006,Putrajaya,MalaysiaEffectsofSSSConDistanceRelayTrippingCharacteristicA.Kazemi,S.JamaliFellow,IEE,andH.Shateri,Member,IEEAbstract-ThispaperpresentsthemeasuredimpedanceattherelayingpointinthepresenceofoneoftheseriesconnectedFlexibleAlternatingCurrentTransmissionSystem(FACTS)devices,i.e.StaticSynchronousSeriesCompensator(SSSC).ThepresenceofSSSConatransmissionlinegreatlyinfluencesthetrippingcharacteristicofdistancerelays.Distancerelaytrippingcharacteristicitselfdependsonthepowersystemstructuralconditions(shortcircuitlevelsatthelineends),pre-faultloading(loadangleandvoltagemagnituderatioofthelineends),andespeciallythegroundfaultresistance.InthepresenceofSSSC,itscontrollingparametersaswellasitsconnectionpointalsoaffectthetrippingcharacteristic.Here,themeasuredimpedanceattherelayingpointiscalculatedduetothementionedaffectingparameters.IndexTerms-Distanceprotection,Faultresistance,FACTSdevices,Trippingcharacteristic,SSSC.I.INTRODUCTIONTHEdistanceprotectionoperationisbasedonthemeasuredimpedanceattherelayingpoint.Thereareseveralfactorsaffectingthemeasuredimpedanceattherelayingpoint.Someofthesefactorsarerelatedtothepowersystemparameterspriortothefaultinstance1-3,whichcanbecategorizedintotwogroups.Firstgroupisthestructuralconditions,representedbytheshortcircuitlevelsatthetransmissionlineends,whereasthesecondgroupistheoperationalconditions,representedbythelineloadangleandthevoltagemagnituderatioatthelineends.Inadditiontothepowersystemparameters,thefaultresistancecouldgreatlyinfluencethemeasuredimpedance,insuchawaythatwhenthefaultresistanceisequaltozero,thepowersystemparametersdonotaffectthemeasuredimpedance.Inotherwords,powersystemparametersaffectthemeasuredimpedanceonlyinthepresenceofthefaultresistance,andasthefaultresistanceincreases,theimpactofpowersystemparametersbecomesmoresevere.Intherecentyears,FACTSdevicesareintroducedtothepowersystemstoincreasethetransmittingcapacityofthelinesandprovidetheoptimumutilizationofthesystemcapability.Thisisdonebypushingthepowersystemstotheirlimits4.It iswelldocumentedintheliteraturethattheintroductionofFACTSdevicesinapowersystemhasagreatinfluenceonitsdynamics.Aspowersystemdynamicschanges,manysub-TheauthorsarewiththeCenterofExcellenceforPowerSystemsAutomationandOperation,DepartmentofElectricalEngineering,IranUniversityofScienceandTechnology(IUST),Narmak16846,Tehran,Iran,(e-mails:kazemiaiust.ac.ir,sjamaliaiust.ac.ir,andshateriaiust.ac.ir).1-4244-0273-5/06/$20.002006IEEEsystemsareaffected,includingtheprotectivesystems.Therefore,itisessentialtostudytheeffectsofFACTSdevicesontheprotectivesystems,especiallythedistanceprotection,whichisthemainprotectivedeviceatEHVandUHVlevels.Unlikethepowersystemparameters,thecontrollingparametersofFACTSdevices,aswellastheirconnectionpointscouldaffectthemeasuredimpedanceeveninthecaseofzerofaultresistance.InthepresenceofFACTSdevices,theconventionaldistancecharacteristicsuchasNM4hoandQuadrilateralaregreatlysubjectedtomal-operationintheformofover-reachingorunder-reachingthefaultpoint.Therefore,theconventionalcharacteristicsmightnotbeusableinthepresenceofFACTSdevices.TheimpactofSTATCOMonthemeasuredimpedancehasbeendiscussedin4,byassumingtheinstantaneousoperationofitscontrollingsystem.TheeffectsofseriesconnectedFACTSdevicesonthemeasuredimpedanceattherelayingpointhavebeenpresentedin5andmoredetailedstudiesforUnifiedPowerFlowController(UPFC)havebeenpresentedin6,whereithasbeenassumedthattheprotectivesystemoperatebeforetheFACTSdevicescontrolsystem.ThispaperpresentsthemeasuredimpedanceattherelayingpointinthepresenceofSSSC.InadditiontothecontrollingparametersofSSSC,themeasuredimpedancedependsonitsconnectionpoint.Therefore,thestudiedconnectingpointsareatthenearend,atthemid-pointandatthefarendofthetransmissionline.Duetothetrippingcharacteristic,itcanbeseenthathowmuchadistancerelayissubjectedtomal-operationinthepresenceofSSSCatthelineendsormid-point.II.SSSCANDITSMODELINGAsmentioned,StaticSynchronousSeriesCompensator(SSSC)isplacedinthegroupofseriesconnectedFACTSdevices.AsshowninFig.1,SSSCconsistsofavoltagesourceinverterconnectedinseriesthroughacouplingtransformertothetransmissionline.AsourceofenergyisrequiredforVoltageSourceInverter(VSI)EnergySourceFig.1.BasicconfigurationofSSSC623Authorized licensed use limited to: NORTH CHINA ELECTRIC POWER UNIVERSITY. 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Restrictions apply.624providingandmaintainingthedcvoltageacrossthedccapacitorandcompensationofSSSClosses7.Fig.2showsthemodelofSSSCwhichconsistsofaseriesconnectedvoltagesourceinserieswithanimpedance.ThisimpedancerepresentstheimpedanceofSSSCcouplingtransformer.VigIVitSFig.2.EquivalentcircuitofSSSCZ15APZ1LF(I(-p)Z1LZ1SBEA()(EBZ2SAPZ2L(IP1-)Z2LZ2SB3Rf4Whentheenergysourceonlyhastheabilityofmaintainingthedcvoltageandsupplyingthelosses,SSSConlycouldcompensatethereactivepower.Inthiscasethemagnitudeofinjectedvoltagecanbecontrolledduetocompensationstrategy,butthephaseangleoftheinjectedvoltagewouldbeperpendiculartothelinecurrent.Theinjectedvoltagecouldeitherleadorlagthelinecurrentby900.III.MEASUREDIMPEDANCEATRELAYINGPOINTDistancerelaysoperatebasedonthemeasuredimpedanceattherelayingpoint.IntheabsenceofSSSCandforzerofaultresistance,themeasuredimpedancebyadistancerelayonlydependsonthelengthofthelinesectionlocatedbetweenthefaultandtherelayingpoints.InFig.3thisimpedanceisequaltoPZL,wherepisperunitlengthofthelinesectionliedbetweenthefaultandtherelayingpoints,andZiListhelinepositivesequenceimpedanceinohms.EAA/7BEBFig.3.EquivalentcircuitforsinglephasetogroundfaultInthecaseofanon-zerofaultresistance,themeasuredimpedanceisnotequaltotheimpedanceofthelinesectionlocatedbetweentherelayingandfaultpoints.Inthiscase,thestructuralandoperationalconditionsofthepowersystemaffectthemeasuredimpedance.Theoperationalconditionspriortothefaultinstancecanberepresentedbytheloadangleoftheline,3,andtheratioofthevoltagemagnitudeatthelineends,h,oringeneralEBREA=hei.Thestructuralconditionsareevaluatedbytheshortcircuitlevelsatthelineends,SSAandSSB.IntheabsenceofSSSCandwithrespecttoFig.3andFig.4,themeasuredimpedanceattherelayingpointcanbeexpressedbythefollowingequations.Moredetailedcalculationscanbefoundin2.ZIAZ1SA+PZ1L(1)Z1BZ1SB+(1P)Z1L(2)ZOAZOSA+PZOL(3)ZOBZOSB+(1P)ZOL(4)Z-2ZlAZlB+ZOAZOB(5)ZlA+ZlBZOA+ZOBZOSAPZOL(I-P)ZOLZOSBFig4.EquvaE=ci=pA=Fig.4.EquivalentcircuitofphaseAtogroundfaultCZB1,-Z1+Z1BCo=ZOBZOA+ZOBKOLZOLZ1LKOL=3ZIL-he-jlIdZAhe+ZlABCld=(ZI+3Rf)Kld3RfZAPZJ1LCR+Cld+2C+Co(l+3KOL)(6)(7)(8)(9)(10)(11)Itcanbeseenwhenthefaultresistanceisequaltozero,themeasuredimpedanceattherelayingpointisequaltotheimpedanceofthelinesectionlocatedbetweentherelayingandthefaultpoints.Thepowersystemconditionsonlyaffectthemeasuredimpedanceattherelayingpointinthepresenceofthefaultresistance.OnceSSSCisintroducedtoapowersystem,theaboveequationswouldvary.ThisvariationnotonlydependsontheSSSCcontrollingparameters,butalsotoitsconnectionpoint.Therefore,themodifiedequationsarepresentedforthreeconnectionpoints,i.e.thenearend,themid-point,andthefarend.Inthefollowingsub-section,SSSCisrepresentedbyitssourcevoltage,Vireiy,anditsseriescouplingtransformerimpedance,ZSSST.A.SSSCinsideFaultLoopOnceSSSCispresentinthefaultloop,(1),(3),(9),(10),and(11)shouldbemodifiedandsomenewonesareintroduced:Z1AZ1+PZL+SSSCZOAZSA+PZOL+ZSSSCZ1AFZISA+PZL+ZSSSCZ1BFZ1SB+(P)Z1L(12)(13)(14)(15)ZISAPI-ILF(IP)I-ILZISBiIAuthorized licensed use limited to: NORTH CHINA ELECTRIC POWER UNIVERSITY. Downloaded on December 3, 2008 at 03:56 from IEEE Xplore. Restrictions apply.Kd=1+re7-he-jZ1AI(l+re)+Z1IFhe+Z1BF(l+rej)CLdSSSC=(Z_+3Rf)KldssscK-IAIheZJh+ZBIjrejVSSSCIZ1AI(1+re)+Z1IFhe+Z1BF(l+rej)Cv=(ZI+3Rf)Kvczsssc3ZSSSC0OKO03Rf-Czsssc-CvssscZAZ+sssc+PZ(L+RCLdSSsc+2C1+Co(1+3KoL)625XOL=1.1478Q/kmZ1SA=8/85Q(16)ZOSA=12/75QZ1SB16/85Q(17)ZOSB=24/Z850Qh=0.96c=160(18)IntheabsenceofSSSC,Fig.5showsthetrippingcharacteristicofthedistancerelay,whichisthemeasuredimpedanceattherelayingpointasthefaultresistancevaries(19)from0to200ohms,whilethefaultlocationchangesfromthe(20)relayingpointuptothefarendofthetransmissionline.100,I(21)ThevariablesZiAI,ZiBI,andZ1IFarerelatedtotheinstallationpositionofSSSC.Itcanbeseenthatevenintheabsenceoffaultresistance,themeasuredimpedanceisnotequaltotheactualimpedanceuptothefaultpoint.B.SSSCoutsideFaultLoopOnceSSSCisnotpresentinthefaultloop,(2),(4),(9),and(11)shouldbemodified,(10)changesto(15)andsomenewonesareintroduced:908070-=60-0504030-20-100050100150200250300350Resistance,R(Ohms)Fig.5.Distancerelaytrippingcharacteristic,withoutSSSC/BI/SB+(1P)L+sssCZOBZOSB+(1P)Z+ZZ1AFZ1SA+IPZLZ1BFZ1SB+(P)ZLSSSC1+rej-he-jKdSSSCZAFhej+ZIF(1+rej)+ZB3Rf(22)ZAPZJL+Cldsssc+2C1+CO(1+3KOL)(27)ThevariablesZiAI,ZiBI,andZ1IFarealsorelatedtotheinstallationpositionofSSSC.Itcanbeseenthatintheabsenceoffaultresistance,themeasuredimpedanceisequaltotheactualimpedanceuptothefaultpoint.IV.EFFECTSOFSSSCONDISTANCERELAYTRIPPINGCHARACTERISTICTheimpactsofthepresenceofSSSConatransmissionlinehavebeentestedforapracticalsystem.A400kVIraniantransmissionlinewithalengthof300kmhasbeenusedinthisstudy.Thestructureofthislineispresentedin8.ByutilizingtheElectro-MagneticTransientProgram(EMTP)9varioussequenceimpedancesofthelineareevaluatedaccordingtoitsphysicaldimensions.Thecalculatedimpedancesandtheotherparametersofthesystemareasfollowing:RiL=0.01133Q/kmXL=0.3037Q/kmROL=0.1535Q/kmNormallythemagnitudeandphaseangleofthevoltagesourceofSSSCiscontrolledaccordingtoitscontrollingstrategy.Therefore,SSSCparameterswouldvarywiththevariationoftheloadingconditionsofthepowersystem.Butinthisstudytheoperationalconditionsofthepowersystemareconsideredtobeconstant,whileitisassumedthattheseconditionsareachievedbythedifferentSSSCoperationalparameters.HerethemagnitudeoftheinjectedvoltagewhetheritleadsorlagsthelinecurrentisutilizedtodescribetheoperationalconditionofSSSC.A.SSSCatNearEndInthiscase,SSSCisalwayspresentinthefaultloop;therefore(21)representthemeasuredimpedance.ThevariablesZiAI,ZiBI,andZ1IFare:JAIIZSA(28)Z1BIZ1SB+Z+Z(29)BSBILSSSCZ1IFPZJL+Zsssc(30)Thetrippingcharacteristicinthecaseofr=0,isshowninFig.6.InthiscaseSSSCdoesnotsupplyorabsorbreactivepower.InFig.6thetrippingcharacteristicwithoutSSSCisalsoshowninthedottedformforcomparison.ItcanbeseenthateveninthecaseofinactiveSSSC,i.e.itsinjectedvoltageiszero;itwouldalsoaffectthemeasuredimpedanceattherelayingpoint.Thisisduetothepresenceofthecouplingtransformerinserieswiththeline.Itcanbeseenthatthetrippingcharacteristicshiftsupward.Themeasuredresistanceincreasesaswellasthemeasuredreactance.Authorized licensed use limited to: NORTH CHINA ELECTRIC POWER UNIVERSITY. 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Restrictions apply.,(0.00)(0.05)(0.10)(0.15)0050100150200250300350Resistance,R(Ohms)Fig.6.Trippingcharacteristic:SSSCatnearend,r=0Fig.7showstheeffectofthevariationofthemagnitudeofSSSCinjectedvoltageonthemeasuredimpedanceattherelayingpointintheleadingmode.Herertakesthevaluesof0.00,0.05,0.10,and0.15200l180160140E1200100i80604020(0.15)(0.10)(0.05)(0.00)050100150200250300350Resistance,R(Ohms)Fig.8.Trippingcharacteristic,SSSCatnearend,laggingmodeB.SSSCatMid-PointInthiscase,SSSCispresentinthefaultloopforthefarhalfoftheline,therefore(21)representthemeasuredimpedance,whileforthenearhalfofthelineSSSCisnotpresentinthefaultloop,so(27)indicatesthemeasuredimpedance.ThevariablesZIA,andZiBIare:ZJAIZ1+I5ZZ1BIZ1S+05Z1+ZSCBSBILSSSCForthefaultsatthenearhalfofthelineZJFis:Z1IF(0.P)Z1L(31)(32)(33)Otherwise,forthefaultsatthefarhalfofthelineZ1JFis:ZIF(PO-.S)Z1L+ZSSSC00100200300400500Resistance,R(Ohms)Fig.7.Trippingcharacteristic,SSSCatnearend,leadingmodeItcanbeseenthatastheinjectedvoltageincreases,themeasuredresistanceincreasesforthehighfaultresistances,whileinthecaseofthelowresistances,themeasuredresistancedecreases;forzerofaultresistanceandhighmagnitudeofinjectedvoltage,eventhemeasuredresistancebecomesnegative.Ontheotherhand,astheinjectedvoltageincreases,themeasuredreactancealsoincreases.Generally,itcanbesaidthatinthepresenceofSSSCintheleadingmodeatthenearendofthetransmissionline,thetrippingcharacteristicturnsinanticlockwisedirection.Fig.8showstheimpactofthevariationofthemagnitudeofSSSCinjectedvoltageonthemeasuredimpedanceattherelayingpointinthelaggingmode.Itcanbeseenthatastheinjectedvoltageincreases,themeasuredresistancedecreasesforthehighfaultresistances,whileinthecaseoflowresistances,themeasuredresistanceincreases.Ontheotherhand,astheinjectedvoltageincreases,themeasuredreactancedecreases.Thereductioninthemeasuredreactanceincreasesforthehigherfaultresistances.Generally,itcanbesaidthatinthepresenceofSSSCinthelaggingmodeatthenearendoftheline,thetrippingcharacteristicturnsinclockwisedirection.(34)Thetrippingcharacteristicforr=0,isshowninFig.9.InFig.9thetrippingcharacteristicwithoutSSSCisalsoshowninthedottedform.1008080-706050403020100050100150200250300350Resistance,R(Ohms)Fig.9.Trippingcharacteristic,SSSCatmid-point,r0ItcanbeseenthatevenifSSSCisnotactive,italsoaffectsthemeasuredimpedanceattherelayingpointintheformofsplittingitintothetwoseparateparts.Thisisalsoduetothepresenceofthecouplingtransformer.Thelowerpartiscorrespondingtothenearhalfoftheline,whiletheupperoneisrelatedtothefarhalf.ThelowerpartisveryclosetothemeasuredimpedanceintheabsenceofSSSC.Theupper100908070vzE60005040302010626100908070vzE605040302010Authorized licensed use limited to: NORTH CHINA ELECTRIC POWER UNIVERSITY. 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Restrictions apply.trippingcharacteristicshiftsupwardandthemeasuredresistanceincreasesaswellasthemeasuredreactance.Fig.10showstheeffectofthevariationofthemagnitudeofSSSCinjectedvoltageonthemeasuredimpedanceattherelayingpointintheleadingmode.200(015)180160-,140O120a1008806040(0.10)005)(0.00)o0I0100200300400500Resistance,R(Ohms)Fig.10.Trippingcharacteristic,SSSCatmid-point,leadingmodeInthecaseoflowercharacteristic,itcanbeseenthatastheinjectedvoltageincreases,themeasuredresistanceincresesaswellasthemeasuredreactance.Forzerofaultresistances,themeasuredimpedanceisfixedanddoesnotchangeastheSSSCinjectedvoltagevaries.Ontheotherhandandinthecaseoftheuppercharacteristic,astheinjectedvoltageincreases,themeasuredresistanceincreasesforthehighfaultresistances,whileinthecaseoflowresistances,themeasuredresistancedecreases.Fortheverylowandzerofaultresistanceandhighmagnitudeofinjectedvoltageeventhemeasuredresistancebecomesnegative,thesameasthecaseofSSSCatthenearend.Otherwise,astheinjectedvoltageincreases,themeasuredreactanceincreases.Generally,itcanbesaidthatinthepresenceofSSSCintheleadingmodeatthemid-pointofthetransmissionline,thetrippingcharacteristicsplitsintothetwoseparateparts,thelowerpartisapproximatelyfixed,whiletheupperpartturnsinanticlockwisedirection.Fig.11showstheeffectofthevariationofthemagnitudeofSSSCinjectedvoltageonthemeasuredimpedanceattherelayingpointinthelaggingmode.1001627Inthecaseoflowercharacteristic,itcanbeseenthatastheinjectedvoltageincreases,themeasuredresistancedecreasesaswellasthemeasuredreactance.Forzerofaultresistances,themeasuredimpedanceisfixedanddoesnotchangeastheSSSCinjectedvoltagevaries.Ontheotherhandandinthecaseofupperpart,astheinjectedvoltageincreases,themeasuredresistancedecreasesforthehighfaultresistances,whileforthelowresistances,themeasuredresistanceincreases.Otherwise,astheinjectedvoltageincreases,themeasuredreactancedecreases.Generally,itcanbesaidthatinthepresenceofSSSCinthelaggingmodeatthemid-pointofthetransmissionline,thetrippingcharacteristicsplitsintothetwoseparatedparts,withoverlappingforhighmagnitudesofinjectedvoltage,thelowerpartisapproximatelyfixed,whiletheupperpartturnsinclockwisedirection.C.SSSCatFarEndInthiscase,SSSCisalwaysnotpresentinthefaultloop;therefore(27)representthemeasuredimpedance.ThevariablesZiAI,ZiBI,andZ1JFare:ZZ+ZJAI1ISAILZ1BIZ1SBSSSCZ1IF(1P)Z1L(35)(36)(37)Thetrippingcharacteristicforr=0,isshowninFig.12.InFig.12thetrippingcharacteristicwithoutSSSCisalsoshowninthedottedform.100807016U050100150200250300350Resistance,R(Ohms)Fig.12.Trippingcharacteristic,SSSCatfarend,r=0=-(0.(0)(0.05)(0.10)(0.15)050100150200250300350Resistance,R(Ohms)Fig.10.Trippingcharacteristic:VTinfront;inactiveSSSCItcanbeseenthatevenifSSSCisnotactive,italsoaffectsthemeasuredimpedanceattherelayingpoint.Thisisduetothepresenceofthecouplingtransformeratthefarendoftheline.Itcanbeseenthatthemeasuredresistancedecreases.Themeasuredreactancedoesnotvaryconsiderably.Fig.13showstheeffectofthevariationofthemagnitudeofSSSCinjectedvoltageonthemeasuredimpedanceattherelayingpointintheleadingmode.Itcanbeseenthatastheinjectedvoltageincreases,themeasuredresistanceandreactancealsoincrease.Forzerofaultresistances,themeasuredimpedanceisfixedanddoesnotchangeastheSSSCinjectedvoltagevaries.908070E60050403020100Authorized licensed use limited to: NORTH CHINA ELECTRIC POWER UNIVERSITY. 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Restrictions apply.628VI.REFERENCES1101009080E7060u504030(0.15)-(0.10);(005)(0.00)20-10050100150200250300350400450500Resistance,R(Ohms)Fig.13.Trippingcharacteristic,SSSCatfarend,leadingmodeFig.14showstheeffectofthevariationofthemagnitudeofSSSCinjectedvoltageonthemeasuredimpedanceattherelayingpointinthelaggingmode.10090(015)(010)(005)(00070O60(D50O403020100050100150200250300350Resistance,R(Ohms)Fig.14.Trippingcharacteristic,SSSCatfarend,laggingmodeItcanbeseenthatastheinjectedvoltageincreases,themeasuredresistanceandreactancedecrease.Forzerofaultresistances,themeasuredimpedanceisfixedanddoesnotchangeastheSSSCinjectedvoltagevaries.V.CONCLUSIONSThispaperpresentsthemeasuredimpedanceattherelayingpointinthepresenceofSSSConthetransmissionline.ThreeconnectionpointshavebeenconsideredfortheSSSC:nearend,mid-point,andfarend.WhenSSSCisnotpresentinthefaultloopandforzerofaultresistance,themeasuredimpedanceattherelayingisequaltotheactualimpedanceofthelinesectionbetweentherelayingandthefaultpoints.Ontheotherhand,whenSSSCinvolvesinthefaultloop,eveninthecaseofzerofaultresistance,themeasuredimpedancewouldbedeviatedfromitsactualvalue.Therefore,whenSSSCisinstalledonaline,oneorbothofitsdistancerelaysaresubjectedtothementioneddeviation.So,theconventionaldistancerelaysareexposedtothemal-operation.Inthesecases,theeffectofSSSContheprotectivezonesshouldbeconsidered.Sincedeviationofthemeasuredimpedanceisnotconstant,becauseofthevariousincludingparameters,adaptivemethodsshouldbeutilized.1ZhangZhizhe,C.Deshu,Anadaptiveapproachindigitaldistanceprotection,IEEETrans.PowerDelivery,vol.6,no.1,pp.135-142,Jan.1991.2Y. Q.Xia,K. K.Li,A.K.David,Adaptiverelaysettingforstand-alonedigitaldistanceprotection,IEEETrans.PowerDelivery,vol.9,no.1,pp.480-491,Jan.1994.3S.Jamali,Afastadaptivedigitaldistanceprotection,inProc.2001IEE7thInternationalConferenceonDevelopmentsinPowerSystemProtection,DPSP2001,pp.149-152.4FanDawei,ZhangChengxue,HuZhijian,WangWei,TheEffectsofFlexibleACTransmissionSystemDeviceonProtectiveRelay,inProc.2002IEEEInternationalConferenceonPowerSystemTechnology,POWERCON2002,vol.4,pp.2608-2611.5P.K.dash,A.K.Pradhan,G.Panda,A.C.Liew,Digitalp