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Foreword

ThiscodeispreparedbyChinaPowerEngineeringConsultingGroupCorporationincollaborationwithassociatedorganizationsasrequiredbytheNoticeonPrintingandDistributingtheDevelopmentandRevisionPlanofNationalStandardsforEngineeringConstruction(secondbatch)for2008(JIANBIAO〔2008〕105)issuedbytheMinistryofHousingandUrban-RuralDevelopment.

Thiscodeisdevelopedafterentensiveinvestigationsandstudies,seriouslygeneralizingkeytechnologiesanddesignsofChina's±800kVDCconverterstationsthathavebeenputintooperationandreferringtothepracticesindesign,constructionandoperationofUHVDCconverterstationsinChina.

Thiscodeisorganizedinto10chaptersandtwoappendices.The10chapatersareGeneral,Terms,SitingofConverterStations,BasicConditionsofACSystemandPerformanceRequirementsforDCTransmissionSystem,ElectricalDesign,DesignofConverterStationControlandProtection,ConverterStationCommunicationDesign,CivilWorksofConverterStations,AuxiliaryEquipmentinConverterStations,andNoiseControlandEnergyConservationofConverterStations.

ThiscodeisadministratedbytheMinistryofHousingandUrban-RuralDevelopmentofthePeople'sRepublicofChina,dailymanagedbyChinalElectricityCouncilandinterpretedbyChinaPowerEngineeringConsultingGroupCorporation.AnyopinionsandsuggestionsproposedduringtheimplementationofthiscodearetobereferredtotheChinaPowerEngineeringConsultingGroupCorporation(atthefollowingaddress:No.65,AndeRoad,XichengDistrict,Beijing,100120)

ChiefDevelopmentOrganizations:

ChinaPowerEngineeringConsultingGroupCorporation

ChinaSouthernPowerGridCo.,Ltd.

ChinaElectricityCouncil

ParticipatingDevelopmentOrganizations:

StateGridCorporationofChina

SouthwestElectricPowerDesignInstituteofChinaPowerEngineeringConsultingGroupCorporation

EastChinaElectricPowerDesignInstituteofChinaPowerEngineeringConsultingGroupCorporation

CentralSouthernChinaElectricPowerDesignInstituteofChinaPowerEngineeringConsultingGroupCorporation

NorthwestElectricPowerDesignInstituteofChinaPowerEngineeringConsultingGroupCorporation

NortheastElectricPowerDesignInstituteofChinaPowerEngineeringConsultingGroupCorporation

NorthChinaPowerEngineeringCo.,Ltd.ofChinaPowerEngineeringConsultingGroupCorporation

GuangdongElectricPowerDesignandResearchInstitute

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ChiefDraftingStaff:

WangJianpingLiPinqingLiuZehongLiBaojinHuJinsongFangJingChenBingGaoLiyingMengXuanWangJingDengChanghong

FengChunyeLeDangjiuXieLongZhangZhengxiangZhaoDaping

YuBoXuYuxiangShenWeihuaRaoBingChenChuanxinXuChangyunZhengPeigangWangWeiLiuQingxinDaiBoNieWeiSuWei

ZhangJinsongYuZhengYuDunyaoYanShihaiLiangBoZengJingZhangYumingMaWangWangChunchengLiuZonghuiSunBangxinGongTiansenHuangYongLuLichengDingYigong

ChiefReviewingStaff:

LiangYanqiaoGuoXianshanShangTaoYinYonghuaDuPengchunGuDingxieHuangChengMaWeiminYangGuofuZhangXieping

ZhangYapingLiWeiHuangXiaomingMuHuaningWuXiaoying

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Contents

1General (1)

2Terms (2)

3SitingofConverterStations (4)

4BasicConditionsofACSystemandPerformanceRequirementsforDCSystem| (5)

4.1BasicConditionsofACSystem (5)

4.2PerformanceRequirementsforDCSystem (5)

5ElectricalDesign (8)

5.1MainElectricalConnection (8)

5.2ArrangementofElectricalEquipment (9)

5.3OvervoltageProtection,InsulationCoordination,andLightningProtection (10)

5.4ExternalInsulationDesignofEquipmentinConverterStations (12)

5.5SelectionofMainEquipment (12)

6DesignofConverterStationControlandProtection (15)

6.1GeneralProvision (15)

6.2Computer-basedMonitoringandControlSystem (15)

6.3DCControlandProtectionSystem (16)

6.4DCLineFaultLocationSystem (17)

6.5DCTransientFaultRecorderSystem (17)

6.6ValveCoolingControlandProtectionSystem (17)

6.7StationAuxiliaryDCPowerSupplyandACUninterruptiblePowerSupply(UPS)System (18)

6.8ImageMonitoringandSafetyGuardingSystem (18)

6.9TimeSynchronizationSystem (18)

7ConverterStationCommunicationDesign (20)

7.1MainCommunicationFacilitiesinConverterStations (20)

7.2SystemCommunication (20)

7.3Intra-stationCommunication (20)

7.4RequirementsforCommunicationPowerSupply,RoomandInterfaces (21)

8CivilWorksofConverterStations (22)

8.1GeneralLayoutandVerticalArrangement (22)

8.2Buildings (25)

8.3Structure (29)

9AuxiliaryEquipmentinConverterStations (32)

9.1Heating,VentilationandAirConditioning (32)

9.2ValveCoolingSystem (33)

9.3WaterSupplySystem (35)

9.4FireDetectionandExtinguishingSystem (35)

10NoiseControlandEnergyConservationofConverterStations (37)

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10.1NoiseControl (37)

10.2EnergyConservation (37)

AppendixAArmonicInterferenceIndexesofACSystems (38)

AppendixBAlculationofEquivalentDisturbingCurrentofDCLines (40)

ExplanationofWordinginThisCode (42)

ListofQuotedStandards (43)

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1General

1.0.1Thiscodeisdevelopedtoregulatethedesignof±800kVDCconverterstationssoastoensuretheycomplywithapplicablenationalpoliciesandregulationsandmeettherequirementsonsafety,reliability,advancement,appliability,economy,andenvironmentalfriendliness.

1.0.2Thiscodeappliestothedesignofconverterstationsof±800kVtwo-terminalDCtransmissionsystem.

1.0.3Theconverterstationsshallbedesignedbasedontheprojectspecificcharacteristics,usingtheavailablenewtechnologies,equipment,materialsandworkmanship.

1.0.4Whendesigningconverterstations,effectivemeasuresshallbetakentoreducelandoccupation,protectenvironmentandensureworksafety.Theenvironmentalprotection,soilandwaterconservation,andworksafetyandhygienefacilitiesshallbedesignedinparallelwiththemainworks.

1.0.5Inadditiontothiscode,thedesignof±800kVconverterstationsshallalsocomplywiththerelevantnationalstandardsinforce.

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2Terms

2.0.1Converter

TheequipmentinconverterstationsusedforAC-DCorDC-ACconversion,alsoknownasconvertervalvegroup.Convertervalvesaregeneralyconnectedinacircuittoconvertcurrent.Aconvertermaybecomprisedofoneormorethree-phasebridgeconvertercircuit(s)(alsoknownassix-pulseconverterorconvertervalvegroup)connectedinseriesorparallel.Twoseries-connectedsix-pulseconverterswitha30°phasedisplacementcanformone12-pulseconverter,alsocalled12-pulseconvertergroup.Byvaryingthetriggeringphasepositionofconvertervalves,aconvertercanbeoperatedinbothrectificationandinversionmode.Specifically,aconverterwhichconvertsalternatingcurrenttodirectcurrentiscalledrectifierwhileaconverterwhichconvertsdirectcurrenttoalternatingcurrentiscalledinverter.Rectifiersandinvertersarebasieallythesameandarecollectivelycalledconverters.Unlessotherwisespecified,"valvegroup"mentionedinthiscoderefersto12-pulseconvertervalvegrouponly.

2.0.2Convertervalve

Thebridgearmservingasthebasicunitofthree-phasebridgeconvertersforcurrentconversioninDCtransmissionsystems,alsocalledsinglevalveunit.InmodernDC-transmission,semi-conductorconvertervalveisagenericnamefofthebridgearmmaincircuitconsistingofseries-orparallel-connectedsemi-conductorpowerelectronicsandtheirassociatedauxiliariescontainedinthesamehousing.

2.0.3Doublevalveunit

Fora12-pulsevalvegroupwiring,ithastwo6-pulsevalvegroupsconnectedinseries,one6-pulsevalvegrouphaseachofitsphasecomposedoftwoconverterarms,andtwoconverterarmsofeachphasearestructurallycloselyconnectedformingavalvetower,knownasadoublevalveunit.

2.0.4Quadruplevalveunit

Fora12-pulsevalvegroupwiring,ithastwosix-pulsevalvegroupsconnectedinseries,onesix-pulsevalvegrouphaseachofitsphasescomposedoftwoconverterarms,andfourconverterarmsofeachphasearestructurallycloselyconnectedformingavalvetower,knownasaquadruplevalveunit.

2.0.5Thyristorvalve

Semi-conductorvalvesconsistingofthyristorelementsandtheirauxiliaries.

2.0.6Valvehall

Buildingsusedtohouseconvertervalves.Theyarethemainbuildingsinconverterstations.Thevalvehallisgenerallyarrangedon12-pulseconverterunitbasis,i.e.,converterbridgesandrelevantequipmentofoneconverterunitarearrangedinaseparatevalvehall.

2.0.7Highvoltagevallhall

Thebuildingwhichhousestheconverterbridgesandassociatedequipmentoftheconverterunitclosetothelinepoleincaseswhereeachpoleconsistsoftwoseries-connected12-pulseconverterunits.

2.0.8Lowvoltagevallhall

Thebuildingwhichhousestheconverterbridgesandassociatedequipmentoftheconverterunit

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closetotheneutralbusincaseswhereeachpoleconsistsoftwoseries-connected12-pulseconverterunits.

2.0.9Auxiliaryequipmentofconverterstation

Otherfacilitiesrequiredtoensurenormaloperationofthemainequipmentofaconverterstation,mainlyincludingauxiliarypowersystem,convertervalvecoolingsystem,valvehallairconditioningsystem,firefightingfacilitiesandstationearth.

2.0.10By-passbreakercircuit

Anelectricalcircuitwhichservestoswitchon/offthe12-pulseconvertervalvegroupconnectedtoitincaseswhereeachpoleconsistsofmultiplevalvegroupsconnectedinseries.Itisgenerallycomprisedofoneby-passcircuitbreaker,disconnectorsformaintenancepurposeonbothsidesofthebreaker,andoneby-passdisonnectorinparallelwiththebreaker.

2.0.11Operationalcontrolmode

Controlmodesadoptedforconverterunits,polesorconverterstationstomaintainoperationalparametersofconverterstationattheexpectedvalues.

2.0.12Additionalcontrolmode

Controlmodesadoptedforconverterunits,polesorconverterstationstohelpmaintainoperationalparametersofACsystemsconnectedtoconverterstationsattheexpectedvalues.

2.0.13Masterstation/slavestation

Inatwo-terminalDCtransmissionsystem,oneconverterstationisdefinedasthemasterstationandtheoppositeonetheslavestation,Thecontrolsystemofthemasterstation,whichisusuallytherectifierstation,receivescontrolordersissuedbythedispatchcenterorstationoperatingpersonnelandsendtheseorderstotheslavestationviathetelecontrolsystem.Themasterstationandslavestationcanbeswitchedoverbetweeneachotherifthetelecontrolsystemisinorder,

2.0.14Telecontrolsystem

ThesystemusedfortransmittingandprocessingtheDCsystemcontrolsignals,protectionsignals,operationsignalsandmonitoringsignalsrequiredtobeexchangedbetweentwoends.

2.0.15Polecontrol

Theequipmentwhichservestocontrolandmonitoronepoleattheconverterstationandgenerallyconsistsofthehostcomputer,I/Omodules,fieldbus,etc.

2.0.16Convertervalveunitcontrol

Controlandmonitoringequipmentprovidedbetweenthepolecontrolandvalvebaseelectronicsonvalvegroupbasis.

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3SitingofConverterStations

3.0.1TheconverterstationsshallbesitedinaccordancewiththesitingrequirementsgiveninDL/T

5218TechnicalCodeforDesigning220kV-500kVSubstationandthroughtechno-economiccomparsionandeconomicbenefitanalysiswhileconsideringthepowersystemplanning,urbanhandruralplanning,contaminationconditions,watersources,transportation,landresource,environmentalprotection,andlocationofearthelectrodeaswellastheprocesscharacteristicsof±800kVconverterstations.

3.0.2Thesitingofconverterstationsshalltakeintoconsiderationtheirimportanceandrolesinthepowersystem.Therectifierstationshouldbelocatednearthepowersourcewhiletheinverterstationneartheloadcenter.Whenmorethanoneconverterstationsaretobebuiltinoneregion,theyshallbesitedconsideringtheeffectsofvariousfactorsonthepowersystem,includingtheelectricaldistancebetweenindividualconverterstations,commonearthelectrode,damagescausedbyexternalforces,etc.

3.0.3Thestationsitesshallbekeptawayfromanyseriouspollutionsources.Whenitisdifficulttodoso,theconverterstationsshallbesitedontheupwindsideoftheprevailingwinddirectiontotheseriouspollutionsourcesandtheireffectsshallbeevaluated.

3.0.4ThesitingshallcomplywithrelevantrequirementsofGB50011CodeforSeismicDesignofBuildingsandGB50021CodeforInvestigationofGeotechnicalEngineering.

3.0.5Thestationsitesshallbeinharmonywithadjacentfacilitiesandsurroundingsandkeptatdistancesfromairports,navigation/stations,satelliteearthstations,mitiliaryfacilities,communicaitonfacilities,andcombustibleandexplosivefacilitiesasspecifiedbyapplieablecurrentnationalstandards.

3.0.6Whenwaterisusedforexternalcoolingofconvertervalves,reliablewatersourcesshallbeavailablenearthestationsites,thevolumeandqualityofwhichshallmeetthedemandofvalvecooling,fire-fightinganddomesticuseattheconverterstation.Thewatersourceshallbeselectedsuchthattheamountofwaterdiversedfromitandusedforotherpurposesisavoidedorreducedtotheminimum.Ifsurfacewaterisused,theguaranteerateofdesignwaterflowindryseasonsshallnotbelowerthan97%,andthewaterqualityshallbeguaranteed.

3.0.7Thestationsitesshouldbeclosetorailways,highways,rivers,andothermeansoftransportation,andgoodtransportationconditionsshallbeavailablefortransportingoversizedequipmentsuchasconvertertransformersandsmmothingreactors.

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4BasicConditionsofACSystemandPerformanceRequirementsforDCSystem

4.1BasicConditionsofACSystem

4.1.1ThebasicdataofACsystemshallinclude:

1VariationrangeofvoltageandfrequencyonACbusinconverterstation;

2Short-circuitcurrentlevelontheACside;

3Negative-sequencepowerfrequencyvoltageandbackgroundharmonicvoltage;

4Faultclearingtimeandsingle-phasereclosingtimesequence.

4.1.2EquivalentACsystemsrequiredforthestudyonDCtransmissionsystemshallinclude:

1EquivalentsystemforAC/DCsimulationstudies;

2EquivalentsystemforstudyonelectromagnetictransientcharacteristicsofAC/DCsystem;

3Equivalentsystemforstudyonreactivepowerswitchingandpowerfrequencyovervoltage;

4EquivalentimpedanceforACfilterperformanceanalysis.

4.2PerformanceRequirementsforDCSystem

4.2.1RatingsoftheDCsystemshallincludetheratedpower,currentandvoltage.

4.2.2OverloadcapabilitiesoftheDCsystemshallincludethecontinuousoverload,short-timeoverload,andtransientoverload.

4.2.3TheminimumpermissibleDCcurrentoftheDCsystemshouldnotexceed10%ofitsratedcurrent.

4.2.4EachpoleoftheDCsystemshallbecapableofoperating/atreducedvoltagewithoutadditionalpowercompensationcapacity.Thereducedoperatingvotagelevelofthesystemshouldbe70%-80%oftheratedDCvoltage.

4.2.5ThepowerreversalcapabilityofaDCtransmissionsystemshallbedeterminedaccordingtosystemrequirements.

4.2.6AbipolarDCtransmissionsystemshallbeabletooperateunderthefollowingbasicmodes:

1Completebipolaroperationmode.

2Incompletebipolaroperationmode.

3Completemonopolarearthreturn.

4Completemonopolarmetallicreturn.

5Incompletemonopolarearthreturn.

6Incompletemonopolarmetallicreturn.

4.2.7Thereactivepowercompensationandvoltagecontrolshallcomplywiththefollowingrequirements:

1TherectifierstationshouldmakefulluseoftheACsystem'sreactivepowersupplycapability,andtheshortfallshallbeprovidedbyinstallingreactivepowercompensationdevicesinthestation.Thereactivepowerconsumedbytheinverterstationshouldbelocallybalanced.IfsurpluscapacitivereactivepoweroccursduetoswitchingonACfilterswhentheDCsystemoperatesatlowloads,theexcess

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portioncanbeabsorbedbytheACsystem.

2DependingontherobustnessoftheACsystemconnectedtoconverterstation,thereactivepowercompensationequipmentshallbeshuntcapacitor,staticVARcompensator,andsynchronouscondenser.Whenshuntcapacitorsareselected,theyshallbedesignedtogetherwithACfilters.

3Allreactivepowercompensationequipmentshouldbedividedintoseveralsub-banks,atleastoneofwhichisforstandby.

4Thecapacityofsub-banksshallmeetthereactivepowerbalancerequirementsaswellasthefollowing:

1)Thechangerateofsteady-stateACbusvoltagecausedbyswitchingofasinglesub-bankshallbewithinthewithstandrangeofthesystemandshallnotcausetheon-loadtapchangerofconvertertransformerstooperate;

2)Theswitchingofanysub-bankshallneitherchangetheDCsystemcontrolmodeortransmittedpower,norcausecommutationfailuresandself-excitationofadjacentsynchronousmotors.

5Thecapacityofreactivepowercompensationequipmentshouldbecalculatedbasedonthelong-termoperatingvoltageofACsystems.

4.2.8Thesub-synchronousresonanceofDCsystemwithadjacentgeneratorsshallbeavoided.

4.2.9TheharmonicinterferenceandfilteringofACsystemshallcomplywiththefollowingrequirements:

1TheharmonicinterferenceonACbusinconverterstationsmaybecharacterizedbysingleharmonicdistortion,totalharmonicdistortionl,andtelephoneharmonicformfactor.TheharmonicinterferenceindexesofACsystemshallcomplywithAppendixAtothiscode,andallharmonicordersupto50shallbeconsidered.For200kV/andaboveACsystems,thesingleharmonicdistortionshouldnotexceed1.0%foroddorders(1.25%for3and5horders)and0.5%forevenorders.Thetotalharmonicdistortionandtelephoneharmonicformfactorshouldnotexceed1.75%and1.0%respectively.

2ACfiltersshallbeconfiguredaccordingtoharmonicsgeneratedbyconverterstation,backgroundharmonicsofACsystems,andharmonicinterferenceindexes.

4.2.10TheharmonicinterferenceandfilteringofDCsystemshallcomplywiththefollowingrequirements:

1TheharmonicinterferenceofDCsystemmaybecharacterizedbytheequivalentdisturbingcurrentofDClines.ItshallbecalculatedinaccordancewithAppendixBtothiscodeandharmonicordersupto50shallbeconsidered.

2Fortwo-terminalDCtransmissionsystemswhichtransmitpowerthroughoverheadlines,DCfiltersshallbeprovidedontheDCsideofconverterstations.TheharmonicinterferenceindexesforDCsystemandconfigurationsofDCfiltersshallbedeterminedaccordingtotheactualconditionsofcommunicationlinesalongtheDClinesofspecificprojects,criteriaforcommunicationnoiseelectromotiveforce,andthestateoftheartofmanufacturingandcostofDCfilters.

3Whennon-characteristicharmonicexcitationsourcesandresonancepointsoccurintheDCsystem,appropriatesuppressionmeasuresshallbetaken.

4.2.11ThepowerlossofconverterstationsshallbedeterminedinaccordancewithrelevantrequirementsinGB/T20989DeterminationofPowerLossesinHigh-VoltageDirectCurrent(HVDC)ConverterStations.

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4.2.12TheaudiblenoisegeneratedbyconverterstationsshallcomplywithrelevantrequirementsinGB/T22075HVDCConverterStationAudibleNoise.

4.2.13ThereliabilityindicatorsofDCtransmissionsystemsshallcomplywiththefollowingrequirements:

1Theforcedenergyunavailability(FEU)shouldnotexceed0.5%.

2Thescheduledenergyunavailability(FEU)shouldnotexceed1.0%.

3Theaverageforcedoutagerateofconverterunitsshouldnotexceedtwotimes/unitperyear.

4Themonopolarforcedoutagerateshouldnotexceedtwotimes/poleperyear.

5Thebipolarforcedoutagerateshouldnotexceed0.1times/year.

4.2.14ThedynamicandtransientperformanceofDCsystemsshallbedeterminedbasedonsystemstudies.

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5ElectricalDesign

5.1MainElectricalConnection

5.1.1Theconstructionscaleofconverterstationsshallbedeterminedthroughsystemjustifications,invovlingtheconsiderationoftheratedpowerandvoltageoftheDCsystem,monopolarandbipolarconfigurations,ACsidevoltage,capacityandbanknumberoffilters,connectionschemeofACsystem,andscaleofoutgoingfeeders.ThemainelectricalconnectionofaconverterstationshallbedesignedbasedonitsscaleandtherequirementsforitsconnectiontotheACsystem.Itshallinvolvetheconnectionofconverterunits,AC/DCswitchyards,ACfilters,reactivepowercompensationequipmentaswellasthestationauxiliarypowersupply.

5.1.2Theelectricalconnectionofconverterunitsshallcomplywiththefollowingrequirements:

1Itshallbedeterminedthroughtechno-economiccomparisonbasedonthethyristorratings,manufacturingtechnologiesandtransportationconditionsofconvertertransformers.

2Theconverterunitshouldusesuchaconnectionschemethatthreesingle-phasetwo-windingconvertertransformersareconnectedwithonethree-phasebridgetypesix-pulserectifiercircuittoformasix-pulseconverterunitandtwosuchunitsareconnectedinseriestoforma12-pusleconverterunit.

3Eachpoleatoneconverterstationshouldhavetwo12-pulseconverterunitsconnectedinseries.

4Each12-pulseconverterunitshallbeprovidedwithby-passcircuitbreakerandby-passdisconnectorsuchthattheswitchingoff,maintenanceandre-switchingonofanyunitwillnotinterruptthepowertransmissionofthehealthyunit.

5.1.3TheelectricalconnectionofAC/DCswtichyardsshallcomplywiththefollowingrequirements:

1TheelectricalconnectionofACswitchyardsshallcomplywiththerelevantrequirementsofcurrentindustrialstandardDL/T5218TechnicalCodeforDesigning220kV-500kVSubstation.

2TheelectricalconnectionofDCswitchyardsshallbebasedonpolebasisand,therefore,theyarerelativelyindependentfromeachother.Theconnectionshallcoversmoothingreactors,DCfilters,neutralbus,linepole,etc.

3TheelectricalconnectionofDCswitchyardsshallservethefollowingfunctions:

1)Enablethesystemtooperateundersuchmodesasbipolaroperation,monopolarearthreturn,andmonopolarmetallicreturn;

2)Isolateandgroundanypoleorconverterunitwhenitismaintained;

3)IsolateandgroundtheDClineofanypolewhenitismaintained;

4)Isolateandgroundtheelectrodeandelectrodelineatoneendorbothendswhentheyaremaintainedincaseswherethesystemoperatesascompleteorincompletemonopolarsystemwithmetallicreturn;

5)Isolateandgroundtheelectrodeandelectrodelineatoneendorbothendswhentheyaremaintainedincaseswherethesystemoperatesasacompletebipolarsystemorincompletebalancedbipolarsystem;

6)EnsurethatwheneitherpoleisinoperationthetransferbetweenearthreturnpathandmetallicreturnpathshallnotinterrupttheDCpowertransmisionandshouldnotreducethe

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transmittedDCpower;

7)Ensurethattheswitchingoffandmaintenanceofafaultypoleorconverterunitshallnotaffectthepowertransmissionofthehealthypoleorconverterunit.

4Thesmoothingreactorsshallbeconfiguredbasedonthemanufacturingtechnologiesandtransportationconditionsofsmoothingreactorsaswellastheovervoltagelevelofconverterstations.Theycaneitherbeconnectedinserieswitheachpole'sDCbus,orrespectivelyinserieswitheachpole's

DCbusandneutralbus.

5.1.4TheelectricalconnectionofACfiltersshallcomplywiththefollowingrequirements:

1InadditiontotherequirementsofDCsystem,theelectricalconnectionofACfiltersshallalsoaccomodatetheconnectionofACsystemsaswellastherequirementsplacedbyACandDCsystemsonACfiltersswitching.

2TheACfiltersshouldbedividedintobanksandthenconnectedtotheACbustowhichtheconverterunitisconnected.

3EarthingswitchesshallbeprovidedbeforeHVcapacitorsofACfilters.

5.1.5Theelectricalconectionofthestationauxiliarypowersystemshallcomplywiththefollowingrequirements:

1Theauxiliarypowershouldconsistofthreecircuitsofpowersourcesindependentofeachother,atleastoneofwhichshallbeconnectedfromtheACsystemintheconverterstation.

2Theauxiliarypowersystemshouldhavetwovoltagelevels,respectively10kVand380/220V.

3TheHVauxiliarypowersystemshallbeofthesectionalizedsingle-busscheme.Theentireconverterstationshouldbeprovidedwithtwooperatingbussectionsandonestandbybussection,eachofwhichshallbepoweredbyoneindependentsource.Sectionalizedswitchesshallbeprovidedbetweentheoepratingandstandbysections.

4TheLVauxiliarypowersystemshouldbeconfiguredaccordingtotheconverterunits.Specifically,eachconverterunit'sLVauxiliarypowersystemshouldbeofsectionalizedsingle-busscheme.ThetwooperatingbussectionsshallbepoweredbydifferentoperatingbussectionsoftheHVauxiliarypowersystem,andsectionalizedswitchesshallbeprovidedbetweenthetwosections.

5.2ArrangementofElectricalEquipment

5.2.1TheACswitchyardshallbearrangedthroughtechno-economiccomparisonbasedonthelay