AC500KvSubstationDesigninChinaAC500千伏变电站的设计外文翻译Word格式文档下载.docx
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1.Introduction
Theresearchanddesignof500kVsubstationsinChinawerestartedin1977,andthefirstsubstationwasputintooperationin1981.Fromthattime,becauseoftherapiddevelopmentofelectricitydemandinChina,designandconstructionof500kVsubstationshaveagreatdevelopment.Especiallyinrecentyears,duetotheincreaseofcapitalinvestmentforpowersystemconstructionfromtheStateGovernment,500kVpowersystemhasdevelopedevenfaster.Till1998about55substations(500kV)werealreadyputintooperation,inwhich217transformerswereinstalled,andthetotalcapacityreached60410MVA.Atpresent,thereare30substationsunderconstruction.Inaddition,ithasbeenplannedtoconstruct/extend30substationsinaccordancewiththepowerdeliveryfromThreeGorgesPowerPlant.
AcompletedesignsystemofAC500kVsubstationinChinahasbeengraduallyestablishedbasedonthepastdesignandconstructionexperiencesandtheuseofnewtechnologies.Thissystemincludesdesignprocedure,designstandards,rulesandregulations,designmanagementandsoon.
Theessentialdesignprinciplesaresafeandreliable,technicallyadvanced,economicalandreasonable,andgoodquality.
2.SizeofSubstations
Chinaisadevelopingcountrywithbroadterritory.Theeconomicdevelopmentisverydifferentfromoneregiontoanother.Inaccordancewiththisfact,the500kVsubstationsizeisdifferentatdifferenttimeandfordifferentregions.
Generallythereareseveralclassesoftransformercapacityinsubstationaccordingtodifferentstagesofconstruction:
Initialstage,MVAFinalstage,MVA
I1X500(750)2>
500(2>
750)
II1X7503X750
川1X750(2X50)4750(1000,1500)
Thenumbersof500kVand220kVoutgoinglinesfromsubstationdifferfromtimetotime.Usuallythereare1-4circuitsof500kVlinesand6-8circuitsof220kVlinesinthefirststageofconstruction,andfinallythenumberreaches6-10circuitsof500kVand12-14circuitsof220kVlines.
Whetherinstallornotthehighvoltagereactorisdecidedbysystematicalinvestigationinovervoltagelevelandlinelength.Reactivecompensationfacilitiesatlowvoltagesideofmaintransformerarealsodesignedinaccordancewiththesystemconditionsandtheprincipleof“compensationonthespotaccordingtotheconditionofeachvoltagelevelandregion.Usua”llyinfirststageofconstructiononlylowvoltageshuntreactorsareinstalled,reservingthepossibilitytoinstallshuntcapacitors.Butsometimes,especiallyinrecentprojects,shuntreactorsandcapacitorsmaybeinstalledsimultaneouslyinfirststageofconstruction.
3.ElectricalDesignFeatures
3.1MainElectricalConnections
Itisveryimportanttoselectmainelectricalconnectionforsafeandreliableoperationandprojectcostcontrol.Themostpopular500kVelectricalconnectionisone-and-halfcircuitbreakerconnection,whichareflexible,reliable,relativelyandlesslandused.Doublesectionalizedbuswithtransferbusconnectionalsobeingemployedinsomeearlyprojects.Inthe11/2CBconnectionconfiguration,sourceandloadcircuitsareusuallyarrangedinpairandinseries,withsametitlecircuitsarrangedindifferentseries.Itispermittedtoconnectthesametitlecircuitstothesamebus,2transformergroupsintoseriesseparatelyandtheother2groupstobusseparately.3currenttransformergroupsareinstalledineveryseriesandsinglephasecapacitivevoltagetransformers(CVT)areinstalledatlineandtransformersides.Specialcalculationsarerequiredtodecideifbusarresterstobeinstalled.Atinitialconstructionstageoutgoinglinesandtransformergroupsuse1-2breakers.For11/2Cbconnection,ifnumberofseriesisequaltoormorethan3atinitialstage,outgoingisolatingswitchesarenotinstalledforthelineandtransformer.Ifthereareonly2seriesintheinitialstage,theyshouldbeinstalled.
Inmostcasesdoublebus(singleordoublesectionalizedbusconnection)withtransferbusschemeareusedin220kVmainelectricalconnections.Insomeprojects11/2CBconnectionisemployed,butinseveralprojectsdoublebuswithouttransferfacilitiesisalsoused.IncaseofdoublebusconnectionsthreephaseCVTareinstalledoneverybussection,singlephaseCVTbeinginstalledinlineside.
Single-busconnectionisusedatmaintransformerlowvoltagesidewithoutoutgoinglinecircuits,onlyreactivecompensationandauxiliarypowersystemcircuitsbeingconnected.Therearethreecasesforthegeneralbreakerat35kVside:
notinstalled,reserveinstallationpositionandinstalled.Likewise,therearetwocasesforbreakerinbranchreactorcircuits:
installedatbussideoratreactorneutralpoint.Aswell,inauxiliarypowersystemcircuitbreakersorlimiting-currentreactorswithfusesmaybeemployed.
TypicalmainelectricalconnectiondiagramsareshowninFig.1.
3.2EquipmentSelection
Theshortcircuitcurrentlevelisusuallycomputedinaccordancewiththesystemdevelopmentplanwithin10-15yearaftersubstationcommissioning.Ingeneralcasesitisselectedas50kA,50kA,40or50kA(31.1kA)for500kV,220kV,35kV(66kV)bus-barrespectively.Atpresenttimeshortcircuitcurrentlevelfor500kVsidereaches62kAinsomesubstations.Theproblem,thatshortcircuitcurrentlevelfor220kVsideinsomesubstationsmayreach63kAinfuture,willbesolvedbyemployingcontrolmeasuresinthesystem,forexample,todividethepowersupplyareaintoparts.
Usuallysingle-phaseauto-transformerswithforcedoilandaircoolingareequipped.Specialsystemvoltageregulationcomputationisneededforemployingon-loadtap-changertransformer.Becauseofthequalityimprovementofdomesticmadetransformer,sparetransformerisusuallynotinstalledinrecentyears.Insomecases,inaccordancewithtransformermanufactureconditions,asparetransformerisnecessaryforsubstationsinthewholeregion.Insomeprojectsthree-phasetransformersareusedaftereconomicalandtechnicalcomparisonintransformerincludingitstransportationconditions.
500kVcircuitbreakersareusuallyceramicpoletypeortanktype.Insomespecialcases,forexample,highaltitude,severeatmosphericpollutionregionsandlimitedsitearea,SFmetalenclosedgasinsulatedswitchgear(GIS)mayalsobeused.Circuitbreakersusuallyhave4-3breaksinonephase,or2inrecentyears.500kVisolatingswitchesareusuallysingle-ordouble-polehorizontalswatch-and-drawtype,whichoccupiesrelativelylesslandarea.500kVcurrenttransformersareoilorSFinsulated.35(or66)kVshuntreactorsareoilimmersedtypeoraircrewdrytype.
Inordertoreduceswitchingovervoltage,500kVinsulationlevelandairgaps,highqualitySFcircuitbreakersandgoodprotectionperformancemetaloxidearrestersareemployed.Incaseofrelativelylonglineitmaybenecessarytoequipclosingresistorsincircuitbreakersaccordingtocomputationstudy.
Theexternalinsulationlevelofelectricalequipmentisselectedaccordingtotheregionalatmosphericpollutionconditions.Usuallytheselectedpollutionclassisnotlowerthann,thatis,theunitleakagedistaneeisnotlessthan20mm/kVfor500kVand220kVapparatus.Theexternalinsulationlevelforneutralungroundedlowvoltagesideshouldbestrengthenedtooneelasshigher.Thegeneralleakagedistaneeisealeulatedbyusingmaximumoperatingvoltage.
3.3InsulationCoordination
InsulationeoordinationisdeterminedinaeeordaneewiththeprineiplesstatedinChinaPowerIndustryStandardDL/T620-1997“OverlargeProteetionandInsulationCoordinationforACEleetriealInstallations.”
Powerfrequeneyovervoltage:
1.3Uxgforsubstationsideoflinebreaker,1.4Uxgforlineside.HereUxgisthemaximumoperatingphasevoltage.
Theeoordinationfaetorbetweennominallightningimpulsewithstandvoltageofeleetriealinstallationsandresiduevoltageofsubstationarrestersundernominaldisehargeeurrentisadoptedas1.4.
Coordinationfaetorbetweennominalphase-to-earthswitehingimpulsewithstandvoltageofeleetriealinstallationinternalinsulationandproteetionlevelofarresterunderswitehingovervoltageshouldnotbelessthan1.15.
3.4Switchyard
Usuallythefollowingbusbartypesareusedin500kVswitehyard:
doublebundlediameter-extendedsoftbuses,supportedthiekaluminumtubebuses,orsuspendedaluminumtubebusesbyVtypeinsulatorstrings.Theswitehyardmaybearrangedinone,twoorthreeoutgoinglinedirectionstypes.Twooutgoingdirectionstypeisusuallyused,andbreakersarearrangedinthreecolumnswithmediumheighttype.Thetransformersareconnectedinserieswithlowframecrossingtype,eachbaywidthbeing28m.Thereareservicepathsbetweenphasesforrepairingtheswitchgear.
For220kVswitchyard,supportedorsuspendedaluminumtubebusesareused.Circusbreakersarearrangedinmediumheighttypeinsingleortwolines,eachbaywidthbeing13or13.5m.Thereareservicepathsbetweencircuitbreakersandcurrenttransformers.
3.5GroundingSystem
Theservicelifeofgroundingsystemsisth