電氣工程及其自動化專業(yè)英語 課件 -Chapter3 Distribution Network

目錄Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4Chapter3DistributionNetworkresidential[,rezi'den??l]adj.住宅的，與住宅有關(guān)的interior[in'ti?ri?]adj.內(nèi)部的，室內(nèi)的enclosure[in'kl?u??]n.外殼meter[mi:t?]n.儀表，vt.用表測量conductive[k?n'd?ktiv]adj.傳導(dǎo)的，導(dǎo)電的generatorrotor.電機(jī)轉(zhuǎn)子splitphase分相socket[‘s?k?t]n.插座galvanizedsteelwire鍍鋅鋼絲generatingstation發(fā)電廠adjacentto鄰近的，毗連的Its

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['θre?h?uld]n.閾值，臨界值，極限amplitude['?mplitju:d]n.振幅oscillation[,?si'lei??n]n.振動，擺動The

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systems.apparentpowerreactivepoweractivepowerResistancepowerABCD提交單選題1分attributableto由于，可歸咎于fluorescentlamps熒光燈protectiverelay保護(hù)繼電器contactor['k?nt?kt?]n.開關(guān)，接觸器equivalentload等效負(fù)荷referencetemperature參考溫度，基準(zhǔn)溫度lightingload電光負(fù)載，照明負(fù)載recloser[ri:'kl?uz?]n.重合閘settingvalue設(shè)定值dispatcher[dis'p?t??]n.調(diào)度員，分配器An"Overcurrent

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['m?dju:l,-d?u:l]n.模塊Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4目錄3.1IntroductionElectricitydistributionisthefinalstageinthedeliveryofelectricitytoendusers.Adistributionsystem'snetworkcarrieselectricityfromthetransmissionsystemanddeliverstoconsumers.Typically,thenetworkwouldincludemedium-voltage(lessthan50

kV)powerlines,substationandpole-mountedtransformers,low-voltage(lessthan1

kV)distributionwiringandsometimesmeters.配電是向終端用戶輸送電力的最后階段。配電系統(tǒng)的網(wǎng)絡(luò)將電力從輸電系統(tǒng)輸送到消費(fèi)者手中。通常，電網(wǎng)將包括中壓(小于50千伏)電力線、變電站和安裝在極點(diǎn)的變壓器、低壓(小于1千伏)配電線路，有時(shí)還包括儀表。3.1IntroductionConductorsfordistributionmaybecarriedonoverheadpolelines,orindensely-populatedareaswheretheyareburiedunderground.Urbanandsuburbandistributionisdonewiththree-phasesystemstoservebothresidential,commercial,andindustrialloads.Distributioninruralareasmaybeonlysingle-phaseifitisnoteconomictoinstallthree-phasepowerforrelativelyfewandsmallcustomers.用于配電的導(dǎo)線可以通過架空電線桿傳送，也可以在人口稠密的地區(qū)埋在地下。城市和郊區(qū)的配電采用三相系統(tǒng)，為住宅、商業(yè)和工業(yè)負(fù)荷提供服務(wù)。如果為相對較少和較小的用戶安裝三相電源不經(jīng)濟(jì)，那么農(nóng)村地區(qū)的配電有可能只是單相的。3.1IntroductionOnlylargeconsumersarefeddirectlyfromdistributionvoltages.Mostutilitycustomersareconnectedtoatransformer,whichreducesthedistributionvoltagetotherelativelylowvoltageusedbylightingandinteriorwiringsystems.Thetransformermaybepole-mountedorsetonthegroundinaprotectiveenclosure.Inruralareas,apole-mounttransformermayserveonlyonecustomer,butinmorebuilt-upareasmultiplecustomersmaybeconnected.只有大容量用戶直接連接到配電網(wǎng)。大多數(shù)用戶連接到變壓器上,（由此）把配電網(wǎng)的電壓降到用于照明和室內(nèi)布線的相對低等級的電壓。變壓器可以安裝在柱上，也可以加保護(hù)外殼后落地安裝。在農(nóng)村地區(qū)，一個(gè)柱上變壓器可能只服務(wù)于一個(gè)用戶，但在更密集的地區(qū)，可能會連接多個(gè)。3.1IntroductionInverydensecityareas,asecondarynetworkmaybeformedwithmanytransformersfeedingintoacommonbusattheutilizationvoltage.Eachcustomerhasan"electricalservice"or"servicedrop"connectionandameterforbilling.(Someverysmallloads,suchasyardlights,maybetoosmalltometerandsoarechargedonlyamonthlyrate.)在密集城區(qū)，可以由許多變壓器以用電電壓饋送到公共母線形成二次配電網(wǎng)。每個(gè)用戶都有接入的“電氣裝置”或者“接線盒”以及一個(gè)用于計(jì)費(fèi)的儀表。(一些非常小的負(fù)荷，如庭院燈，可能太小而無法計(jì)量，因此只按月收費(fèi)。)3.1IntroductionAgroundconnectiontolocalearthisnormallyprovidedforthecustomer'ssystemaswellasfortheequipmentownedbytheutility.Thepurposeofconnectingthecustomer'ssystemtogroundistolimitthevoltagethatmaydevelopifhighvoltageconductorsfallonthelower-voltageconductors,orifafailureoccurswithinadistributiontransformer.Ifallconductiveobjectsarebondedtothesameearthgroundingsystem,theriskofelectricshockisminimized.用戶的系統(tǒng)以及電力公司的設(shè)備通常都接地。將用戶的系統(tǒng)接地的目的是限制高壓導(dǎo)體到低壓導(dǎo)體之間的電勢差或者配網(wǎng)變壓器故障時(shí)可能產(chǎn)生的電壓。如果所有導(dǎo)體都在同一個(gè)接地系統(tǒng)中，可將觸電危險(xiǎn)降到最低。3.1IntroductionHowever,multipleconnectionsbetweentheutilitygroundandcustomergroundcanleadtostrayvoltageproblems;customerpiping,swimmingpoolsorotherequipmentmaydevelopobjectionablevoltages.Theseproblemsmaybedifficulttoresolvesincetheyoftenoriginatefromplacesotherthanthecustomer'spremises.然而，電力公司地和用戶地之間的多次連接會導(dǎo)致雜散電壓問題;用戶設(shè)有電路的水槽、游泳池或其他設(shè)備可能會產(chǎn)生令人反感的電壓（漏電）。這些問題可能很難解決，因?yàn)樗鼈兺ǔ碜杂脩綦娋W(wǎng)之外的地方。3.1IntroductionInmanyareas,"delta"threephaseserviceiscommon.Deltaservicehasnodistributedneutralwireandthereforeitislessexpensive.InNorthAmericaandLatinAmerica,threephaseserviceisoftenaY(wye)inwhichtheneutralisdirectlyconnectedtothecenterofthegeneratorrotor.在許多領(lǐng)域，三角形的三相連接較常見。三角形接法沒有分布式中性線，因此成本較低。在北美和拉丁美洲，三相連接通常是Y型(星形接線)，其中中性點(diǎn)直接連接到發(fā)電機(jī)轉(zhuǎn)子的中心。3.1IntroductionTheneutralprovidesalow-resistancemetallicreturntothedistributiontransformer.Wyeserviceisrecognizablewhenalinehasfourconductors,oneofwhichislightlyinsulated.Three-phasewyeserviceisexcellentformotorsandheavypoweruse.中性點(diǎn)為配電變壓器提供低電阻的金屬回路。星型接線很容易辨認(rèn):一條線路有四根導(dǎo)線，其中一根輕度絕緣。三相星形連接非常適合電機(jī)和大功率場合使用。3.1IntroductionManyareasintheworldusesingle-phase220

Vor230

Vresidentialandlightindustrialservice.Inthissystem,thehighvoltagedistributionnetworksuppliesafewsubstationsperarea,andthe230Vpowerfromeachsubstationisdirectlydistributed.Ahotwireandneutralareconnectedtothebuildingfromonephaseofthreephaseservice.Single-phasedistributionisusedwheremotorloadsaresmall.世界上許多地區(qū)使用單相220V或230V住宅和輕工業(yè)服務(wù)。在本系統(tǒng)中，高壓配電網(wǎng)為每個(gè)區(qū)域供電幾個(gè)變電站，每個(gè)變電站直接分配230V的電力?；鹁€和中性點(diǎn)線從單相或三相電源連接到建筑物。單相配電用于電機(jī)負(fù)載小的地方。3.1IntroductionIntheU.S.,partsofCanadaandLatinAmerica,splitphaseserviceisthemostcommon.Splitphaseprovidesboth120Vand240Vservicewithonlythreewires.Thehousevoltagesareprovidedbylocaltransformers.Theneutralisdirectlyconnectedtothethree-phaseneutral.Socketvoltagesareonly120V,but240Visavailableforheavyappliancesbecausethetwohalvesofaphaseopposeeachother.在美國、加拿大部分地區(qū)和拉丁美洲，分階段服務(wù)是最常見的。分相提供120V和240V的服務(wù)，只有三根線。室內(nèi)電壓由本地變壓器提供。中性點(diǎn)與三相中性點(diǎn)直接相連。插座電壓只有120V，但240V可用于重型電器，因?yàn)橐粋€(gè)相位的兩半相互對立。3.1IntroductionJapanhasalargenumberofsmallindustrialmanufacturers,andthereforesuppliesstandardlow-voltagethreephase-serviceinmanysuburbs.Also,Japannormallysuppliesresidentialserviceastwophasesofathreephaseservice,withaneutral.Theyworkwellforbothlightingandmotors.日本有大量的小型工業(yè)制造商，因此在許多郊區(qū)提供標(biāo)準(zhǔn)的低壓三相服務(wù)。此外，日本通常向住宅提供三相中的兩相，中間加個(gè)中性點(diǎn)。它們適用于照明和馬達(dá)。3.1IntroductionRuralservicesnormallytrytominimizethenumberofpolesandwires.Single-wireearthreturn(SWER)istheleastexpensive,withonewire.Ituseshighvoltages,whichinturnpermituseofgalvanizedsteelwire.Thestrongsteelwirepermitsinexpensivewidepolespacings.Otherareasusehighvoltagesplit-phaseorthreephaseserviceathighercost.農(nóng)村服務(wù)通常會盡量減少電線桿和電線的數(shù)量。單線接地回路(SWER)是最便宜的，只有一根線。它的高壓高，這個(gè)等級的電壓允許使用鍍鋅鋼絲。堅(jiān)固的鋼絲可以用經(jīng)濟(jì)的大跨距桿。其他地區(qū)采用高壓分相或三相供電，成本較高。3.1IntroductionElectricitymetersusedifferentmeteringequationsdependingontheformofelectricalservice.Sincethemathdiffersfromservicetoservice,thenumberofconductorsandsensorsinthemetersalsovary.電表根據(jù)電力服務(wù)的形式使用不同的計(jì)量公式。由于服務(wù)間的計(jì)算方法不同，儀表中導(dǎo)體和傳感器的數(shù)量也不同。3.1IntroductionBesidesreferringtothephysicalwiring,thetermelectricalservicealsorefersinanabstractsensetotheprovisionofelectricitytoabuilding.除了指物理布線外，“電力服務(wù)”一詞還抽象地指向建筑物提供電力。Inthischapter,distributionnetworkstructure,loadmodelanddistributionautomationsystemwillbeintroduced.本章將介紹配電網(wǎng)結(jié)構(gòu)、負(fù)荷模型和配電網(wǎng)自動化系統(tǒng)。Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4目錄3.2.1

PrimaryDistributionSystems

Thewiringbetweenthegeneratingstationandthefinaldistributionpointiscalledtheprimarydistributionsystem.Thereareseveralmethodsusedfortransmittingthepowerbetweenthesetwopoints.Thetwomostcommonmethodsaretheradialsystemandtheloopsystem.電站和最終配電點(diǎn)之間的布線稱為一次配電系統(tǒng)。在這兩點(diǎn)之間傳輸電能有幾種方法。兩種最常用的方法是放射式系統(tǒng)和環(huán)網(wǎng)系統(tǒng)。3.2.1

PrimaryDistributionSystems

A.TheRadialSystemThetermradialcomesfromthewordradiate,whichmeanstosendoutoremitfromonecentralpoint.Aradialsystemisanelectricaltransmissionsystemwhichbeginsatacentralstationandsuppliespowertovarioussubstations.A.放射式系統(tǒng)放射狀這個(gè)詞來源于放射狀這個(gè)詞，意思是從一個(gè)中心點(diǎn)發(fā)出或發(fā)射。放射式系統(tǒng)是一種電力傳輸系統(tǒng)，它從一個(gè)中心站開始，向各個(gè)變電站供電。3.2.1

PrimaryDistributionSystems

Initssimplestform,aradialsystemconsistsofageneratingstationwhichproducestheelectricalenergy.Thisenergyistransmittedfromthegenerator(s)tothecentralstation,whichisgenerallypartof,oradjacentto,thegeneratingstation.Atthecentralstation,thevoltageissteppeduptoahighervalueforlong-distancetransmission.在其最簡單的形式中，放射式系統(tǒng)由一個(gè)產(chǎn)生電能的發(fā)電站組成。電能從發(fā)電機(jī)傳輸?shù)街行碾娬?中心電站通常是發(fā)電廠的一部分或在發(fā)電廠附近。中心電站將電壓升到更高的等級用于遠(yuǎn)距離傳輸。3.2.1

PrimaryDistributionSystems

Fromthecentralstation,severallinescarrythepowertovarioussubstations.Atthesubstations,thevoltageisusuallyloweredtoavaluemoresuitablefordistributiontopopulatedareas.Fromthesubstations,linescarrythepowertodistributiontransformers.Thesetransformerslowerthevoltagestothevaluerequiredbytheconsumer.從中心站，幾條線路將電力輸送到各個(gè)變電站。在變電站，電壓通常降低到一個(gè)更適合分配到人口稠密地區(qū)的值。從變電站，線路將電力輸送到配電變壓器。這些變壓器將電壓降低到用戶所需的值。3.2.1

PrimaryDistributionSystems

B.TheLoopSystemTheloopsystemstartsfromthecentralstationorasubstationandmakesacompleteloopthroughtheareatobeserved,andbacktothestartingpoint.Thisresultsintheareabeingsuppliedfrombothends,allowingsectionstobeisolatedincaseofabreakdown.Anexpandedversionoftheloopsystemconsistsofseveralcentralstationsjoinedtogethertoformaverylargeloop.B.循環(huán)系統(tǒng)環(huán)網(wǎng)系統(tǒng)從中心站或變電站開始，通過服務(wù)區(qū)域形成完整的環(huán)路，并返回起點(diǎn)。這導(dǎo)致該區(qū)域由兩端供電，允許在發(fā)生故障時(shí)隔離各部分。環(huán)線系統(tǒng)的擴(kuò)展版本由幾個(gè)中心站連接在一起形成一個(gè)非常大的環(huán)線。3.2.2

ConsumerDistributionSystems

Thetypeofdistributionsystemthat"theconsumerusestotransmitpowerwithinthepremisesdependsupontherequirementsoftheparticularinstallation.Residentialoccupanciesgenerallyusethesimplesttype.Commercialandindustrialsystemsvarywidelywithloadrequirements.消費(fèi)者用來在房屋內(nèi)傳輸電力的配電系統(tǒng)的類型取決于特定裝置的要求。住宅占用一般采用最簡單的類型。商業(yè)和工業(yè)系統(tǒng)因負(fù)載要求而有很大差異。3.2.2

ConsumerDistributionSystems

A.Single-phaseSystemsMostsingle-phasesystemsaresuppliedfromathree-phaseprimary.Theprimaryofasingle-phasetransformerisconnectedtoonephaseofthethree-phasesystem.Thesecondarycontainstwocoilsconnectedinserieswithamidpointtaptoprovideasingle-phase,three-wiresystem.Thisarrangementisgenerallyusedtosupplypowertoresidentialoccupanciesandsomecommercialestablishments.AschematicdiagramisshowninFig.3.1.A.單相系統(tǒng)大多數(shù)單相系統(tǒng)由三相主變供電。單相變壓器的一次電源連接到三相系統(tǒng)的一相。次級系統(tǒng)包含兩個(gè)線圈，通過中點(diǎn)抽頭串聯(lián)起來，形成單相三線制系統(tǒng)。這種安排通常用于住宅和一些商業(yè)場所供電。原理圖如圖3.1所示。3.2.2

ConsumerDistributionSystems

Forresidentialoccupancies,theserviceconductorsareinstalledeitheroverheadorunderground.Single-familyandsmallmultifamilydwellingshavethekilowatt-hourmetersinstalledontheoutsideofthebuilding.Fromthekilowatt-hourmeter,theconductorsareconnectedtothemaindisconnect.Fig.3.2(a)and3.2(b)showthisarrangement.對于住宅，導(dǎo)線按架空線或敷設(shè)電纜均可。單戶住宅和小型多戶住宅的電度表安裝在建筑物的外部。從電度表上，導(dǎo)體連接到主控上。圖3.2(a)和3.2(b)顯示了這種排列。3.2.2

ConsumerDistributionSystems

Threeseparatedisconnectingmeansareusedwithonecommonground.三種不同的斷開方式使用同一接地。Fig.3.1Single-phase,three-wire,120/240Vsystem圖3.1單相三線制120/240v制3.2.2

ConsumerDistributionSystems

（a）Single-familyresidencewithathree-wire,single-phaseservice(b)Three-wire,single-phaseservicefoeamultifamilydwellingFig.3.2Kilowatt-hourmeterinstalledforresidentialoccupancies(a)三線單相服務(wù)的單戶住宅(b)多戶住宅三線單相供電圖3.2住宅用電量電能表安裝情況3.2.2

ConsumerDistributionSystems

Fromthemaindisconnect,theconductorssupplypowertothebranchcircuitpanels.Fordwellingoccupancies,therearethreebasictypesofbranchcircuits:generallightingcircuits,smallapplianceandlaundrycircuits,andindividualbranchcircuits.Theindividualbranchcircuitsarefrequentlyusedtosupplycentralheatingand/orair-conditioningsystems,waterheaters,andotherspecialloads.導(dǎo)體從主控處向分支電路面板供電。對于住宅設(shè)施，有三種基本類型的分支電路:一般照明電路，小型電器和洗衣電路，以及單獨(dú)的分支電路。單個(gè)分支電路經(jīng)常用于供應(yīng)中央供暖和/或空調(diào)系統(tǒng)、熱水器和其他特殊負(fù)載。3.2.2

ConsumerDistributionSystems

B.GroundingRequirementsAllACservicesarerequiredtobegroundedonthesupplysideoftheservicedisconnectingmeans.Thisgroundingconductorrunsfromthecombinationsystemandequipmentgroundtothegroundingelectrode.Formultifamilyoccupancies,itispermittedtouseuptosixservicedisconnectingmeans.Asinglegroundingconductorofadequatesizeshouldbeusedforthesystemground(seeFig.3.2(b)).B.接地要求所有交流連接都要求在連接斷開裝置的供電側(cè)接地。該接地導(dǎo)體從組合系統(tǒng)和設(shè)備的地一直連接到接地電極。對于多戶住宅，允許使用多達(dá)六種連接斷開方式。系統(tǒng)接地應(yīng)采用足夠尺寸的單根接地導(dǎo)體(見圖3.2(b))。3.2.3

CommercialandIndustrialInstallations

Commercialandindustrialinstallationsaremorecomplexthansmallresidentialinstallations.Largeapartmentcomplexesandcondominiums,althoughclassifiedasresidentialoccupancies,oftenusecommercial-styleservices.Asingle-phase,three-wireserviceorathree-phase,four-wireservicemaybebroughtintothebuilding,generallyfromunderground.Theservice-entranceconductorsterminateisamaindisconnect.商業(yè)和工業(yè)裝置比小型住宅裝置更復(fù)雜。大型公寓和共管公寓雖然被歸類為住宅，但往往采用商業(yè)風(fēng)格的服務(wù)。單相三線制供電或三相四線制供電通常從地下進(jìn)入建筑物。進(jìn)線口導(dǎo)線端子是一個(gè)主要的斷開點(diǎn)。3.2.3

CommercialandIndustrialInstallations

Fromthispoint,theconductorsareconnectedtotheindividualkilowatt-hourmetersforeachapartmentandthentosmallerdisconnectingmeansandover-currentprotectivedevices.Branch-circuitpanelsaregenerallyinstalledineachapartment.Feederconductorsconnecttheindividualdisconnectingmeanstothebranch-circuitpanels.Commercialand/orindustrialbuildingsmayhavemorethanonekilowatt-hourmeter,dependinguponthenumberofoccupancies.從這一點(diǎn)開始，連接到每戶公寓的出線都經(jīng)過各自的電度表，然后再接小容量的斷路裝置和過流保護(hù)裝置。分支電路面板一般安裝在每個(gè)公寓。饋線導(dǎo)體將各個(gè)斷路裝置連接到分支電路面板上。商業(yè)及/或工業(yè)樓宇可能有不止一個(gè)千瓦時(shí)電表，視住戶數(shù)目而定。3.2.3

CommercialandIndustrialInstallations

Theservicesizesvaryaccordingtothedemand.Theserviceisusuallyathree-phase,four-wiresystem.Theavailablevoltagesmaybe120/208Vor277/480V.Ifthesystemprovides277/480V,atransformermustbeinstalledinordertoobtain120V.Ifthebuildingcoversalargearea,itisrecommendedthattheservicebeinstallednearthecenterofthebuilding.Thisarrangementminimizeslinelossonfeederandbranch-circuitconductors.服務(wù)的大小根據(jù)需求而不同。該服務(wù)通常是三相四線制系統(tǒng)?？捎秒妷簽?20/208v或277/480v。如果系統(tǒng)提供277/480v電壓，則必須安裝變壓器以獲得120V電壓。如果建筑物占地面積較大，建議將服務(wù)安裝在建筑物中心附近。這種布置將饋線和分支電路導(dǎo)體上的線路損耗降至最低。3.2.3

CommercialandIndustrialInstallations

Someutilitiessupplyathree-phase,three-wireorthree-phase,four-wiredeltasystem.Thecommonvoltagesthatmaybeobtainedfromthethree-wiredeltasystemare240V,440V,or550V.Withthisarrangement,atransformermustbeusedtoobtain120V.Theusualvoltagessuppliedfromthefour-wiredeltasystemare240V,threephasesand120V,singlephase.一些電力公司提供三相三線制或三相四線制delta系統(tǒng)?？梢詮娜€三角系統(tǒng)中獲得的常用電壓為240V,440V或550V。在這種情況下，必須使用變壓器來獲得120V的電壓。四線制三角系統(tǒng)通常提供的電壓為三相240V和單相120V。3.2.3

CommercialandIndustrialInstallations

Manylargeconsumerspurchasetheelectricalenergyattheprimaryvoltage,andtransformersareinstalledontheirpremises.Three-phasevoltagesupto15kVareoftenused.許多大用戶在一次電壓下購買電能，變壓器就安裝在他們的房子里。通常使用15千伏以下的三相電壓。3.2.3

CommercialandIndustrialInstallations

Theserviceforthistypeofinstallationgenerallyconsistsofmetalcubiclescalledasubstationunit.Thetransformersareeitherinstalledwithinthecubicleoradjacenttoit.Isolationswitchesofthedrawertypeareinstalledwithinthecubicle.Theseswitchesareusedtoisolatethemainswitchorcircuitbreakerfromthesupplyduringmaintenanceorrepair.這種類型的安裝服務(wù)通常由稱為變電站單元的金屬隔間組成。變壓器要么安裝在隔間內(nèi)，要么安裝在隔間附近。抽屜式隔離開關(guān)安裝在隔間內(nèi)。這些開關(guān)用于在維護(hù)或維修期間將主開關(guān)或斷路器與電源隔離。3.2.4

ConsumerLoopSystems

Althoughtheradialsystemofdistributionisprobablythemostcommonlyusedsystemoftransmittingpowerontheconsumer’sproperty,theloopsystemisalsoemployed.AblockdiagramofbothsystemisillustratedinFig.3.3(a)and3.3(b).Thereareseveralvariationsofthesesystemsinuseintheindustry,butthesystemsillustratedhereshowthebasicstructure.盡管放射式配電系統(tǒng)可能是用戶財(cái)產(chǎn)上最常用的輸電系統(tǒng)，但環(huán)網(wǎng)系統(tǒng)也被采用。兩個(gè)系統(tǒng)的框圖如圖3.3(A)和3.3(b)所示。在工業(yè)中使用的這些系統(tǒng)有幾種變體，但這里所示的系統(tǒng)顯示了基本結(jié)構(gòu)。3.2.4

ConsumerLoopSystems

Fig.3.3(b)Consumerloopdistributionsystem圖3.3(b)消費(fèi)者回路分配系統(tǒng)3.2.4

ConsumerLoopSystems

Wheninstallinganysystem,over-currentprotectionandgroundingmustbegivenprimaryconsideration.ElectricalpersonnelwhodesignandinstallthesesystemsmustcomplywiththeNECandlocalrequirements.Disconnectingmeansmaybeinstalledanywhereinthedistributionlooptoprovideforisolatingsections.在安裝任何系統(tǒng)時(shí)，必須首先考慮過流保護(hù)和接地。設(shè)計(jì)和安裝這些系統(tǒng)的電氣人員必須符合NEC和當(dāng)?shù)氐囊?。斷開裝置可以安裝在配電回路的任何地方，以提供隔離部分。3.2.5

SecondaryHigh-voltageDistributionLargeindustrialestablishmentsmayfinditmoreeconomicaltodistributepoweratvoltageshigherthan600V.Dependinguponthetypeofinstallationandtheloadrequirements,voltagesashighas2300Vmaybeused.Step-downtransformersareinstalledinstrategiclocationstoreducethevoltagetoapracticalworkingvalue.Adiagramofahigh-voltageradialsystemisshowninFig.3.4.大型工業(yè)機(jī)構(gòu)可能會發(fā)現(xiàn)在高于600伏的電壓下分配電力更經(jīng)濟(jì)。根據(jù)安裝類型和負(fù)荷需求,可能需要2300V的電壓。在關(guān)鍵位置安裝降壓變壓器將電壓降低到實(shí)際工作電壓值。高壓放射式接線系統(tǒng)示意圖如圖3.4所示。3.2.5

SecondaryHigh-voltageDistributionFig3.4Secondaryhigh-voltageradialdistributionsystem圖3.4二次高壓放射式接線配電系統(tǒng)3.2.5

SecondaryHigh-voltageDistributionSometimesthehigh-voltage(primary)systemmayberadial,andthelow-voltage(secondary)systemmaybeconnectedintoaloop.Anothermethodistohaveboththeprimariesandsecondariesconnectedtoformaloop.Fig.3.5(a)andFig.3.5(b)showthesemethods.有時(shí)高壓(一次)系統(tǒng)可能放射式接線，低壓(二次)系統(tǒng)可能連接成閉環(huán)。另一種方法是將主次線連接起來形成閉環(huán)。圖3.5(a)和圖3.5(b)顯示了這些方法。3.2.6

SecondaryTiesLoopSystemItisfrequentlyconvenienttoconnectloadstothesecondaryconductorsatpointsbetweentransformers.Theseconductorsarecalledsecondaryties.Article450oftheNECgivesspecificrequirementsregardingtheconductorsizesandover-currentprotection.多數(shù)情況下從接入點(diǎn)點(diǎn)將負(fù)載連接到變壓器之間也是很方便的。這些導(dǎo)線稱為二次連接。NEC第450條對導(dǎo)體尺寸和過流保護(hù)給出了具體要求。3.2.6

SecondaryTiesLoopSystemFig3.5(a)Secondaryhigh-voltagedistributionsystem;high-voltageradical；low-voltageloop圖3.5(a)二次高壓配電系統(tǒng);高壓自由基；低壓回路3.2.6

SecondaryTiesLoopSystemFig3.5(b)Consumerdistributionsystemwithhigh-voltageandlow-voltageloops圖3.5(b)高壓回路和低壓回路的配電系統(tǒng)Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4目錄3.3.1

StaticLoadModelsInthisandotherloadmodelsdescribedinthissection,在這個(gè)和本節(jié)中描述的其他負(fù)載模型中，3.3.1

StaticLoadModelsWherePandQareactiveandreactivecomponentsoftheloadwhenthebusvoltagemagnitudeisV.Thesubscriptoidentifiesthevaluesoftherespectivevariablesattheinitialoperatingcondition.式中，當(dāng)母線電壓幅值單位為V時(shí)，P和Q為負(fù)載的有功分量和無功分量，下標(biāo)0表示初始運(yùn)行條件下各變量的值。3.3.1

StaticLoadModelsTheparametersofthismodelaretheexponentsaandb.Withtheseexponentsequalto0,1，or2,themodelrepresentsconstantpower,constantcurrent,orconstantimpedancecharacteristics,respectively.Forcompositeloads,theirvaluesdependontheaggregatecharacteristicsofloadcomponents.該模型的參數(shù)為指數(shù)a和b，當(dāng)指數(shù)分別為0、1和2時(shí)，該模型分別代表恒功率、恒電流和恒阻抗特性。對于綜合負(fù)載，它們的值取決于荷載分量的總體特性。3.3.1

StaticLoadModelsTheexponenta(orb)isnearlyequaltotheslopedP/dV(ordQ/dV)atV=V0.Forcompositesystemloads,theexponentausuallyrangesbetween0.5and1.8;theexponentbistypicallybetween1.5and6.Asignificantcharacteristicoftheexponentbisthatitvariesasanonlinearfunctionofvoltage.Thisiscausedbymagneticsaturationindistributiontransformersandmotors.Athighervoltages,Qtendstobesignificantlyhigher.指數(shù)a(或b)幾乎等于在V=V0時(shí)dP/dV(或dQ/dV)的斜率。對于復(fù)合系統(tǒng)負(fù)載，指數(shù)a通常在0.5到1.8之間;指數(shù)b通常在1.5到6之間。指數(shù)b的一個(gè)重要特征是它作為電壓的非線性函數(shù)而變化。這是由配電變壓器和電動機(jī)中的磁飽和引起的。在更高的電壓下，Q趨于顯著更高。3.3.1

StaticLoadModelsIntheabsenceofspecificinformation,themostcommonlyacceptedstaticloadmodelistorepresentactivepowerasconstantcurrent(i.e.,a=l)andreactivepowerasconstantimpedance(i.e.,b=2).在沒有具體信息的情況下，最普遍接受的靜態(tài)負(fù)載模型是將有功功率表示為恒流(即a=l)，無功功率表示為恒阻抗(即b=2)。Analternativemodelwhichhasbeenwidelyusedtorepresentthevoltagedependencyofloadsisthepolynomialmodel:另一種被廣泛用于表示負(fù)載電壓依賴性的模型是多項(xiàng)式模型:3.3.1

StaticLoadModelsThismodeliscommonlyreferredtoastheZIPmodel,asitiscomposedofconstantimpedance(Z),constantcurrent(I),andconstantpower(P)components.Theparametersofthemodelarethecoefficientsp1top3andq1toq3,whichdefinetheproportionofeachcomponent.該模型通常被稱為ZIP模型，因?yàn)樗珊愣ㄗ杩?Z)，恒定電流(I)和恒定功率(P)組成。模型的參數(shù)為系數(shù)p1~p3和q1~q3，分別定義了各成分所占的比例。3.3.1

StaticLoadModelsThefrequencydependencyofloadcharacteristicsisusuallyrepresentedbymultiplyingtheexponentialmodelorthepolynomialmodelbyafactorasfollows:負(fù)荷特性的頻率依賴性通常用指數(shù)模型或多項(xiàng)式模型乘以一個(gè)因子來表示，如下所示:3.3.1

StaticLoadModelsWhereΔfisthefrequencydeviation(f-f0).Typically,KPfrangesfrom0to3.0,andKqfrangesfrom-2.0to0.Thebusfrequencyfisusuallynotastatevariableinthesystemmodelusedforstabilityanalysis.Therefore,itisevaluatedbycomputingthetimederivativeofthebusvoltageangle.其中Δf為頻率偏差(f-f0)。一般情況下，KPf的取值范圍是0~3.0,Kqf的取值范圍是-2.0~0。在用于穩(wěn)定性分析的系統(tǒng)模型中，母線頻率f通常不是狀態(tài)變量。因此，通過計(jì)算母線電壓角的時(shí)間導(dǎo)數(shù)來評估。3.3.1

StaticLoadModelsAcomprehensivestaticmodelwhichofferstheflexibilityofaccommodatingseveralformsofloadrepresentationisasfollows:一個(gè)全面的靜態(tài)模型提供了靈活性，以適應(yīng)幾種形式的負(fù)載表示如下:Theexpressionforthereactivecomponentoftheloadhasasimilarstructure.Thereactivepowercompensationassociatedwiththeloadisrepresentedseparately.負(fù)載的無功分量的表達(dá)式具有類似的結(jié)構(gòu)。與負(fù)荷相關(guān)的無功補(bǔ)償分別表示。3.3.1

StaticLoadModelsThestaticmodelsgivenbyEquations3.1to3.6arenotrealisticatlowvoltages,andmayleadtocomputationalproblems.Therefore,stabilityprogramsusuallymakeprovisionsforswitchingtheloadcharacteristictotheconstantimpedancemodelwhenthebusvoltagefallsbelowaspecifiedvalue.式3.1至3.6給出的靜態(tài)模型在低電壓下不符合實(shí)際，可能導(dǎo)致計(jì)算問題。因此，穩(wěn)定性程序通常規(guī)定，當(dāng)母線電壓低于規(guī)定值時(shí)，將負(fù)載特性切換到恒定阻抗模型。3.3.1

StaticLoadModelsIntheloadmodelusedintheEPRIExtendedTransient/MidtermStabilityProgram(ETMSP),theexponentsa1,a2,b1,andb2arevariedasafunctionofvoltagebelowathresholdvalueofbusvoltage,andtheconstantpowerandconstantcurrentcomponentsareswitchedtoconstantimpedancerepresentation.在EPRI擴(kuò)展暫態(tài)/中長期穩(wěn)定程序中的負(fù)荷模型中，當(dāng)電壓方程中的電壓低于母線電壓閾值時(shí)，通過改變變量a1、a2、b1、b2的值，恒功率和恒電流元件可以轉(zhuǎn)為恒阻抗（模型）。3.3.2

DynamicLoadModelsTheresponseofmostcompositeloadstovoltageandfrequencychangesisfast,andthesteadystateoftheresponseisreachedveryquickly.Thisistrueatleastformodestamplitudesofvoltage/frequencychange.Theuseofstaticmodelsdescribedintheprevioussectionsisjustifiedinsuchcases.大多數(shù)復(fù)合負(fù)載對電壓和頻率變化的響應(yīng)是快速的，并且很快達(dá)到穩(wěn)態(tài)。至少這對電壓/頻率變化的振幅是正確的。在這種情況下，前面章節(jié)中描述的靜態(tài)模型的使用是合理的。3.3.2

DynamicLoadModelsThereare,however,manycaseswhereitisnecessarytoaccountforthedynamicsofloadcomponents.Studiesofinterareaoscillations,voltagestability,andlong-termstabilityoftenrequireloaddynamicstobemodeled.Studyofsystemswithlargeconcentrationsofmotorsalsorequiresrepresentationofloaddynamics.然而，在許多情況下，有必要考慮負(fù)載元件的動態(tài)過程。區(qū)域間振蕩、電壓穩(wěn)定性和長期穩(wěn)定性的研究通常需要對負(fù)載動力學(xué)進(jìn)行建模。研究大量電機(jī)集中的系統(tǒng)也需要用負(fù)載動力學(xué)表示。3.3.2

DynamicLoadModelsTypically,motorsconsume60to70%ofthetotalenergysuppliedbyapowersystem.Therefore,thedynamicsattributabletomotorsareusuallythemostsignificantaspectsofdynamiccharacteristicsofsystemloads.通常情況下，電機(jī)消耗電力系統(tǒng)提供的總能量的60-70%。因此，電機(jī)的動態(tài)特性通常是系統(tǒng)負(fù)載動態(tài)特性中最重要的方面。Otherdynamicaspectsofloadcomponentsthatrequireconsiderationinstabilitystudiesincludethefollowing:在穩(wěn)定性研究中需要考慮的負(fù)荷的其他動態(tài)方面包括:3.3.2

DynamicLoadModels(a)Extinctionofdischargelampsbelowacertainvoltageandtheirrestartwhenthevoltagerecovers.Dischargelampsincludemercuryvapour,sodiumvapour,andfluorescentlamps.Theseextinguishatvoltagesintherangeof0.7to0.8pu.Whenthevoltagerecovers,theyrestartafterIor2secondsdelay.(a)低于一定電壓的放電燈熄滅，電壓恢復(fù)后重新啟動。放電燈包括汞蒸氣、鈉蒸氣和熒光燈。這些在0.7至0.8普的電壓范圍內(nèi)熄滅。當(dāng)電壓恢復(fù)后，它們在1或2秒后重新啟動。3.3.2

DynamicLoadModels(b)Operationofprotectiverelays,suchasthermalandovercurrentrelays.Manyindustrialmotorshavestarterswithelectromagneticallyheldcontactors.Thesedropsopenatvoltagesintherangeof0.55to0.75pu;thedropouttimeisontheorderofafewcycles.Smallmotorsonrefrigeratorsandairconditionershaveonlythermaloverloadprotections,whichtypicallytripinabout10to30seconds.(b)保護(hù)繼電器的操作，如熱繼電器和過電流繼電器。許多工業(yè)電機(jī)的起動器都帶有電磁接觸器。他們在0.55至0.75pu的電壓范圍內(nèi)跳開;跳開時(shí)間大約是幾個(gè)周期。冰箱和空調(diào)上的小電機(jī)只有熱過載保護(hù)，通常在10到30秒內(nèi)跳閘。3.3.2

DynamicLoadModels(c)Thermostaticcontrolorloads,suchasspaceheaters/coolers,waterheaters,andrefrigerators.Suchloadsope