变电站设计外文翻译-毕业设计

外文文献一GeneralRequirementstoConstructionofSubstationSubstationsareavitalelementinapowersupplysystemofindustrialenterprises．Theyservetoreceive，convertanddistributeelectricenergy.Dependingonpowerandpurpose,thesubstationsaredividedintocentraldistributionsubstationsforavoltageof110-500kV;mainstep-downsubstationsfor110-220/6-10-35kV;deepentrancesubstationsfor110-330/6-10Kv;distributionsubstationsfor6-10Kv;shoptransformersubstationsfor6-10/0.38-0.66kV.Atthemainstep-downsubstations,theenergyreceivedfromthepowersourceistransformedfrom110-220kVusuallyto6-10kV(sometimes35kV)whichisdistributedamongsubstationsoftheenterpriseandisfedtohigh-voltageservices.Centraldistributionsubstationsreceiveenergyfrompowersystemsanddistributeit(withoutorwithpartialtransformation)viaaerialandcablelinesofdeepentrancesatavoltageof110-220kVovertheenterpriseterritory.Centraldistributionsubstationdiffersfromthemaindistributionsubstationinahigherpowerandinthatbulkofitspowerisatavoltageof110-220kV;itfeaturessimplifiedswitchingcircuitsatprimaryvoltage;itisfedfromthepowertoanindividualobjectorregion.Low-andmedium-powershopsubstationstransformenergyfrom6-10kVtoasecondaryvoltageof380/220or660/380.Step-uptransformersubstationsareusedatpowerplantsfortransformationofenergyproducedbythegeneratorstoahighervoltagewhichdecreaseslossesatalong-distancetransmission.ConvertersubstationsareintendedtoconvertACtoDC(sometimesviceversa)andtoconvertenergyofonefrequencytoanother.Convertersubstationswithsemiconductorrectifiersareconvertenergyofonefrequencytoanother.Convertersubstationswithsemiconductorrectifiersaremosteconomic.Distributionsubstationsfor6-10kVarefedprimarilyfrommaindistributionsubstations(sometimesfromcentraldistributionsubstations).Withasystemofdividingsubstationsfor110-220kV,thefunctionsofaswitch-gearareaccomplishedbyswitch-gearsfor6-10kVatdeepentrancesubstations.Dependingonlocationofsubstationstheirswitch-gearmaybeoutdoororindoor.Thefeedandoutputlinesat6-10kVsubstationsaremainlyofthecabletype.at35-220kVsubstationsoftheaerialtype.Whenerectingandwiringthesubstations,majorattentionisgiventoreliableandeconomicpowersupplyofagivenproduction.Substationsareerectedbyindustrialmethodswiththeuseoflargeblocksandassembliespreparedatthesiteshopsofelectricengineeringorganizationsandfactoriesofelectricalengineeringindustry.Substationsareusuallydesignedforoperationwithoutcontinuousattendanceofthedutypersonnelbutwiththeuseofelementaryautomaticandsignalingdevices.Whenconstructingthestructuralpartofasubstation.itisadvisabletouselight-weightindustrialstructuresandelements(panels,floors,etc.)madeofbentsections.Theseelementsarepre-madeoutsidetheerectionzoneandareonlyassembledatsite.Thisconsiderablycutsthetermsandcostofconstruction.Basiccircuitryconceptsofsubstationsarechosenwhendesigningapowersupplysystemoftheenterprise.Substationsfeatureprimaryvoltageentrances.transformersandoutputcablelinesorcurrentconductorsofsecondaryvoltage.Substationsaremountedfromequipmentandelementsdescribedbelow.Thenumberofpossiblecombinationsofequipmentandelementsisverygreat.Whenelaboratingasubstationcircuitry,itisnecessarytostriveformaximumsimplificationandminimizingthenumberofswitchingdevices.Suchsubstationsaremorereliableandeconomic.Circuitryissimplifiedbyusingautomaticreclosureorautomaticchangeovertoreservefacilitywhichallowsrapidandfaultlessredundancyofindividualelementsandusingequipment.Whendesigningtransformersubstationsofindustrialenterprisesforallvoltages,thefollowingbasicconsiderationsaretakenintoaccount:1.Preferableemploymentofasingle-bussystemwithusingtwo-bussystemsonlytoensureareliableandeconomicpowersupply;2.Wideuseofunitizedconstructionsandbuslesssubstations;3.Substantiatedemploymentofautomaticsandtelemetry;ifthesubstationdesigndoesnotenvisagetheuseofautomaticsortelemetry,thecircuitryissoarrangedastoallowforaddingsuchequipmentinfuturewithoutexcessiveinvestmentsandre-work.4.Useofsimpleandcheapdevices-isolatingswitches,short-circuitingswitches,load-breakingisolators,fuses,withdueregardfortheirswitchingcapacitymaydrasticallycuttheneedforexpensiveandcriticaloil,vacuum,solenoidandairswitches.Substationandswitch-gearcircuitriesaresomadethatusingtheequipmentofeachproductionlineisfedfromindividualtransformers,assemblies,thelinestoallowtheirdisconnectionsimultaneouslywithmechanismswithoutdisruptingoperationofadjacentproductionflows.Whenelaboratingcircuitryofasubstation,themostvitaltaskistoproperlychooseandarrangeswitchingdevices(switches,isolators,currentlimiters,arresters,high-voltagefuses).Thedecisiondependsonthepurpose,powerandsignificanceofthesubstation.Manyyearsago,scientistshadveryvagueideasaboutelectricity.Manyofthemthoughtofitasasortoffluidthatflowedthroughwiresaswaterflowsthroughpipes,buttheycouldnotunderstandwhatmadeitflow.Manyofthemfeltthatelectricitywasmadeupoftinyparticlesofsomekind,buttryingtoseparateelectricityintoindividualparticlesbaffledthem.Then,thegreatAmericanscientistMillikan,in1909,astoundedthescientificworldbyactuallyweighingasingleparticleofelectricityandcalculatin