AC500KvSubstationDesigninChinaAC500千伏变电站的设计外文翻译Word格式文档下载.docx

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