电气工程及其自动化专业英语 课件 -Chapter3 Distribution Network、chapter 4 Measurement and Control in Power system、Chapter 5 High Voltage Direc

目录Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4Chapter3DistributionNetworkresidential[,rezi'denʃəl]adj.住宅的，与住宅有关的interior[in'tiəriə]adj.内部的，室内的enclosure[in'kləuʒə]n.外壳meter[mi:tə]n.仪表，vt.用表测量conductive[kən'dʌktiv]adj.传导的，导电的generatorrotor.电机转子splitphase分相socket[‘sɒkɪt]n.插座galvanizedsteelwire镀锌钢丝generatingstation发电厂adjacentto邻近的，毗连的Its

natural

frequency

fallsintotwoparts

when

the

loads

exerted

on

()

are

asymmetrical.

Dual

resonance

phenomenon

appears

based

on

the

former

single

frequency

vibration.

generatorrotorgeneratorstatorgeneratorcoregeneratorwindingABCD提交单选题1分loopsystem闭环系统disconnect[,diskə'nekt]n.断开处groundingelectrode接地电极over-currentprotectivedevices过流保护装置feeder['fi:də]馈线，支线radialsystem放射状系统complywith遵守step-downtransformer降压变压器loadcharacteristic负载特性，负载特性曲线distributionfeeder配电馈线voltageregulator电压调节器

They

will

tie

the

()in

with

thepower

system.transformersubstationgeneratingstationturbineboilerABCD提交单选题1分activepower有功功率reactivepower无功功率aggregate['æɡriɡət,'æɡriɡeit]adj.聚合的，集合的magneticsaturation磁性饱和polynomial[,pɔli'nəumiəl]adj.多项式的frequencydeviation频率偏差stabilityanalysis稳定性分析threshold

['θreʃhəuld]n.阈值，临界值，极限amplitude['æmplitju:d]n.振幅oscillation[,ɔsi'leiʃən]n.振动，摆动The

()

control

is

of

greatimportance

for

the

safe

and

stable

operation

of

power

systems.apparentpowerreactivepoweractivepowerResistancepowerABCD提交单选题1分attributableto由于，可归咎于fluorescentlamps荧光灯protectiverelay保护继电器contactor['kɔntæktə]n.开关，接触器equivalentload等效负荷referencetemperature参考温度，基准温度lightingload电光负载，照明负载recloser[ri:'kləuzə]n.重合闸settingvalue设定值dispatcher[dis'pætʃə]n.调度员，分配器An"Overcurrent

relay"

is

a

type

of

()whichoperates

when

the

load

current

exceeds

apreset

value.solidstaterelayelectromagneticrelaythermorelayprotectiverelayABCD提交单选题1分masterstation主站，主控台，总机scatterance散布analog

['ænəlɔɡ]adj.模拟的module

['mɔdju:l,-dʒu:l]n.模块Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4目录3.1IntroductionElectricitydistributionisthefinalstageinthedeliveryofelectricitytoendusers.Adistributionsystem'snetworkcarrieselectricityfromthetransmissionsystemanddeliverstoconsumers.Typically,thenetworkwouldincludemedium-voltage(lessthan50

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

kV)distributionwiringandsometimesmeters.配电是向终端用户输送电力的最后阶段。配电系统的网络将电力从输电系统输送到消费者手中。通常，电网将包括中压(小于50千伏)电力线、变电站和安装在极点的变压器、低压(小于1千伏)配电线路，有时还包括仪表。3.1IntroductionConductorsfordistributionmaybecarriedonoverheadpolelines,orindensely-populatedareaswheretheyareburiedunderground.Urbanandsuburbandistributionisdonewiththree-phasesystemstoservebothresidential,commercial,andindustrialloads.Distributioninruralareasmaybeonlysingle-phaseifitisnoteconomictoinstallthree-phasepowerforrelativelyfewandsmallcustomers.用于配电的导线可以通过架空电线杆传送，也可以在人口稠密的地区埋在地下。城市和郊区的配电采用三相系统，为住宅、商业和工业负荷提供服务。如果为相对较少和较小的用户安装三相电源不经济，那么农村地区的配电有可能只是单相的。3.1IntroductionOnlylargeconsumersarefeddirectlyfromdistributionvoltages.Mostutilitycustomersareconnectedtoatransformer,whichreducesthedistributionvoltagetotherelativelylowvoltageusedbylightingandinteriorwiringsystems.Thetransformermaybepole-mountedorsetonthegroundinaprotectiveenclosure.Inruralareas,apole-mounttransformermayserveonlyonecustomer,butinmorebuilt-upareasmultiplecustomersmaybeconnected.只有大容量用户直接连接到配电网。大多数用户连接到变压器上,（由此）把配电网的电压降到用于照明和室内布线的相对低等级的电压。变压器可以安装在柱上，也可以加保护外壳后落地安装。在农村地区，一个柱上变压器可能只服务于一个用户，但在更密集的地区，可能会连接多个。3.1IntroductionInverydensecityareas,asecondarynetworkmaybeformedwithmanytransformersfeedingintoacommonbusattheutilizationvoltage.Eachcustomerhasan"electricalservice"or"servicedrop"connectionandameterforbilling.(Someverysmallloads,suchasyardlights,maybetoosmalltometerandsoarechargedonlyamonthlyrate.)在密集城区，可以由许多变压器以用电电压馈送到公共母线形成二次配电网。每个用户都有接入的“电气装置”或者“接线盒”以及一个用于计费的仪表。(一些非常小的负荷，如庭院灯，可能太小而无法计量，因此只按月收费。)3.1IntroductionAgroundconnectiontolocalearthisnormallyprovidedforthecustomer'ssystemaswellasfortheequipmentownedbytheutility.Thepurposeofconnectingthecustomer'ssystemtogroundistolimitthevoltagethatmaydevelopifhighvoltageconductorsfallonthelower-voltageconductors,orifafailureoccurswithinadistributiontransformer.Ifallconductiveobjectsarebondedtothesameearthgroundingsystem,theriskofelectricshockisminimized.用户的系统以及电力公司的设备通常都接地。将用户的系统接地的目的是限制高压导体到低压导体之间的电势差或者配网变压器故障时可能产生的电压。如果所有导体都在同一个接地系统中，可将触电危险降到最低。3.1IntroductionHowever,multipleconnectionsbetweentheutilitygroundandcustomergroundcanleadtostrayvoltageproblems;customerpiping,swimmingpoolsorotherequipmentmaydevelopobjectionablevoltages.Theseproblemsmaybedifficulttoresolvesincetheyoftenoriginatefromplacesotherthanthecustomer'spremises.然而，电力公司地和用户地之间的多次连接会导致杂散电压问题;用户设有电路的水槽、游泳池或其他设备可能会产生令人反感的电压（漏电）。这些问题可能很难解决，因为它们通常来自用户电网之外的地方。3.1IntroductionInmanyareas,"delta"threephaseserviceiscommon.Deltaservicehasnodistributedneutralwireandthereforeitislessexpensive.InNorthAmericaandLatinAmerica,threephaseserviceisoftenaY(wye)inwhichtheneutralisdirectlyconnectedtothecenterofthegeneratorrotor.在许多领域，三角形的三相连接较常见。三角形接法没有分布式中性线，因此成本较低。在北美和拉丁美洲，三相连接通常是Y型(星形接线)，其中中性点直接连接到发电机转子的中心。3.1IntroductionTheneutralprovidesalow-resistancemetallicreturntothedistributiontransformer.Wyeserviceisrecognizablewhenalinehasfourconductors,oneofwhichislightlyinsulated.Three-phasewyeserviceisexcellentformotorsandheavypoweruse.中性点为配电变压器提供低电阻的金属回路。星型接线很容易辨认:一条线路有四根导线，其中一根轻度绝缘。三相星形连接非常适合电机和大功率场合使用。3.1IntroductionManyareasintheworldusesingle-phase220

Vor230

Vresidentialandlightindustrialservice.Inthissystem,thehighvoltagedistributionnetworksuppliesafewsubstationsperarea,andthe230Vpowerfromeachsubstationisdirectlydistributed.Ahotwireandneutralareconnectedtothebuildingfromonephaseofthreephaseservice.Single-phasedistributionisusedwheremotorloadsaresmall.世界上许多地区使用单相220V或230V住宅和轻工业服务。在本系统中，高压配电网为每个区域供电几个变电站，每个变电站直接分配230V的电力。火线和中性点线从单相或三相电源连接到建筑物。单相配电用于电机负载小的地方。3.1IntroductionIntheU.S.,partsofCanadaandLatinAmerica,splitphaseserviceisthemostcommon.Splitphaseprovidesboth120Vand240Vservicewithonlythreewires.Thehousevoltagesareprovidedbylocaltransformers.Theneutralisdirectlyconnectedtothethree-phaseneutral.Socketvoltagesareonly120V,but240Visavailableforheavyappliancesbecausethetwohalvesofaphaseopposeeachother.在美国、加拿大部分地区和拉丁美洲，分阶段服务是最常见的。分相提供120V和240V的服务，只有三根线。室内电压由本地变压器提供。中性点与三相中性点直接相连。插座电压只有120V，但240V可用于重型电器，因为一个相位的两半相互对立。3.1IntroductionJapanhasalargenumberofsmallindustrialmanufacturers,andthereforesuppliesstandardlow-voltagethreephase-serviceinmanysuburbs.Also,Japannormallysuppliesresidentialserviceastwophasesofathreephaseservice,withaneutral.Theyworkwellforbothlightingandmotors.日本有大量的小型工业制造商，因此在许多郊区提供标准的低压三相服务。此外，日本通常向住宅提供三相中的两相，中间加个中性点。它们适用于照明和马达。3.1IntroductionRuralservicesnormallytrytominimizethenumberofpolesandwires.Single-wireearthreturn(SWER)istheleastexpensive,withonewire.Ituseshighvoltages,whichinturnpermituseofgalvanizedsteelwire.Thestrongsteelwirepermitsinexpensivewidepolespacings.Otherareasusehighvoltagesplit-phaseorthreephaseserviceathighercost.农村服务通常会尽量减少电线杆和电线的数量。单线接地回路(SWER)是最便宜的，只有一根线。它的高压高，这个等级的电压允许使用镀锌钢丝。坚固的钢丝可以用经济的大跨距杆。其他地区采用高压分相或三相供电，成本较高。3.1IntroductionElectricitymetersusedifferentmeteringequationsdependingontheformofelectricalservice.Sincethemathdiffersfromservicetoservice,thenumberofconductorsandsensorsinthemetersalsovary.电表根据电力服务的形式使用不同的计量公式。由于服务间的计算方法不同，仪表中导体和传感器的数量也不同。3.1IntroductionBesidesreferringtothephysicalwiring,thetermelectricalservicealsorefersinanabstractsensetotheprovisionofelectricitytoabuilding.除了指物理布线外，“电力服务”一词还抽象地指向建筑物提供电力。Inthischapter,distributionnetworkstructure,loadmodelanddistributionautomationsystemwillbeintroduced.本章将介绍配电网结构、负荷模型和配电网自动化系统。Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4目录3.2.1

PrimaryDistributionSystems

Thewiringbetweenthegeneratingstationandthefinaldistributionpointiscalledtheprimarydistributionsystem.Thereareseveralmethodsusedfortransmittingthepowerbetweenthesetwopoints.Thetwomostcommonmethodsaretheradialsystemandtheloopsystem.电站和最终配电点之间的布线称为一次配电系统。在这两点之间传输电能有几种方法。两种最常用的方法是放射式系统和环网系统。3.2.1

PrimaryDistributionSystems

A.TheRadialSystemThetermradialcomesfromthewordradiate,whichmeanstosendoutoremitfromonecentralpoint.Aradialsystemisanelectricaltransmissionsystemwhichbeginsatacentralstationandsuppliespowertovarioussubstations.A.放射式系统放射状这个词来源于放射状这个词，意思是从一个中心点发出或发射。放射式系统是一种电力传输系统，它从一个中心站开始，向各个变电站供电。3.2.1

PrimaryDistributionSystems

Initssimplestform,aradialsystemconsistsofageneratingstationwhichproducestheelectricalenergy.Thisenergyistransmittedfromthegenerator(s)tothecentralstation,whichisgenerallypartof,oradjacentto,thegeneratingstation.Atthecentralstation,thevoltageissteppeduptoahighervalueforlong-distancetransmission.在其最简单的形式中，放射式系统由一个产生电能的发电站组成。电能从发电机传输到中心电站,中心电站通常是发电厂的一部分或在发电厂附近。中心电站将电压升到更高的等级用于远距离传输。3.2.1

PrimaryDistributionSystems

Fromthecentralstation,severallinescarrythepowertovarioussubstations.Atthesubstations,thevoltageisusuallyloweredtoavaluemoresuitablefordistributiontopopulatedareas.Fromthesubstations,linescarrythepowertodistributiontransformers.Thesetransformerslowerthevoltagestothevaluerequiredbytheconsumer.从中心站，几条线路将电力输送到各个变电站。在变电站，电压通常降低到一个更适合分配到人口稠密地区的值。从变电站，线路将电力输送到配电变压器。这些变压器将电压降低到用户所需的值。3.2.1

PrimaryDistributionSystems

B.TheLoopSystemTheloopsystemstartsfromthecentralstationorasubstationandmakesacompleteloopthroughtheareatobeserved,andbacktothestartingpoint.Thisresultsintheareabeingsuppliedfrombothends,allowingsectionstobeisolatedincaseofabreakdown.Anexpandedversionoftheloopsystemconsistsofseveralcentralstationsjoinedtogethertoformaverylargeloop.B.循环系统环网系统从中心站或变电站开始，通过服务区域形成完整的环路，并返回起点。这导致该区域由两端供电，允许在发生故障时隔离各部分。环线系统的扩展版本由几个中心站连接在一起形成一个非常大的环线。3.2.2

ConsumerDistributionSystems

Thetypeofdistributionsystemthat"theconsumerusestotransmitpowerwithinthepremisesdependsupontherequirementsoftheparticularinstallation.Residentialoccupanciesgenerallyusethesimplesttype.Commercialandindustrialsystemsvarywidelywithloadrequirements.消费者用来在房屋内传输电力的配电系统的类型取决于特定装置的要求。住宅占用一般采用最简单的类型。商业和工业系统因负载要求而有很大差异。3.2.2

ConsumerDistributionSystems

A.Single-phaseSystemsMostsingle-phasesystemsaresuppliedfromathree-phaseprimary.Theprimaryofasingle-phasetransformerisconnectedtoonephaseofthethree-phasesystem.Thesecondarycontainstwocoilsconnectedinserieswithamidpointtaptoprovideasingle-phase,three-wiresystem.Thisarrangementisgenerallyusedtosupplypowertoresidentialoccupanciesandsomecommercialestablishments.AschematicdiagramisshowninFig.3.1.A.单相系统大多数单相系统由三相主变供电。单相变压器的一次电源连接到三相系统的一相。次级系统包含两个线圈，通过中点抽头串联起来，形成单相三线制系统。这种安排通常用于住宅和一些商业场所供电。原理图如图3.1所示。3.2.2

ConsumerDistributionSystems

Forresidentialoccupancies,theserviceconductorsareinstalledeitheroverheadorunderground.Single-familyandsmallmultifamilydwellingshavethekilowatt-hourmetersinstalledontheoutsideofthebuilding.Fromthekilowatt-hourmeter,theconductorsareconnectedtothemaindisconnect.Fig.3.2(a)and3.2(b)showthisarrangement.对于住宅，导线按架空线或敷设电缆均可。单户住宅和小型多户住宅的电度表安装在建筑物的外部。从电度表上，导体连接到主控上。图3.2(a)和3.2(b)显示了这种排列。3.2.2

ConsumerDistributionSystems

Threeseparatedisconnectingmeansareusedwithonecommonground.三种不同的断开方式使用同一接地。Fig.3.1Single-phase,three-wire,120/240Vsystem图3.1单相三线制120/240v制3.2.2

ConsumerDistributionSystems

（a）Single-familyresidencewithathree-wire,single-phaseservice(b)Three-wire,single-phaseservicefoeamultifamilydwellingFig.3.2Kilowatt-hourmeterinstalledforresidentialoccupancies(a)三线单相服务的单户住宅(b)多户住宅三线单相供电图3.2住宅用电量电能表安装情况3.2.2

ConsumerDistributionSystems

Fromthemaindisconnect,theconductorssupplypowertothebranchcircuitpanels.Fordwellingoccupancies,therearethreebasictypesofbranchcircuits:generallightingcircuits,smallapplianceandlaundrycircuits,andindividualbranchcircuits.Theindividualbranchcircuitsarefrequentlyusedtosupplycentralheatingand/orair-conditioningsystems,waterheaters,andotherspecialloads.导体从主控处向分支电路面板供电。对于住宅设施，有三种基本类型的分支电路:一般照明电路，小型电器和洗衣电路，以及单独的分支电路。单个分支电路经常用于供应中央供暖和/或空调系统、热水器和其他特殊负载。3.2.2

ConsumerDistributionSystems

B.GroundingRequirementsAllACservicesarerequiredtobegroundedonthesupplysideoftheservicedisconnectingmeans.Thisgroundingconductorrunsfromthecombinationsystemandequipmentgroundtothegroundingelectrode.Formultifamilyoccupancies,itispermittedtouseuptosixservicedisconnectingmeans.Asinglegroundingconductorofadequatesizeshouldbeusedforthesystemground(seeFig.3.2(b)).B.接地要求所有交流连接都要求在连接断开装置的供电侧接地。该接地导体从组合系统和设备的地一直连接到接地电极。对于多户住宅，允许使用多达六种连接断开方式。系统接地应采用足够尺寸的单根接地导体(见图3.2(b))。3.2.3

CommercialandIndustrialInstallations

Commercialandindustrialinstallationsaremorecomplexthansmallresidentialinstallations.Largeapartmentcomplexesandcondominiums,althoughclassifiedasresidentialoccupancies,oftenusecommercial-styleservices.Asingle-phase,three-wireserviceorathree-phase,four-wireservicemaybebroughtintothebuilding,generallyfromunderground.Theservice-entranceconductorsterminateisamaindisconnect.商业和工业装置比小型住宅装置更复杂。大型公寓和共管公寓虽然被归类为住宅，但往往采用商业风格的服务。单相三线制供电或三相四线制供电通常从地下进入建筑物。进线口导线端子是一个主要的断开点。3.2.3

CommercialandIndustrialInstallations

Fromthispoint,theconductorsareconnectedtotheindividualkilowatt-hourmetersforeachapartmentandthentosmallerdisconnectingmeansandover-currentprotectivedevices.Branch-circuitpanelsaregenerallyinstalledineachapartment.Feederconductorsconnecttheindividualdisconnectingmeanstothebranch-circuitpanels.Commercialand/orindustrialbuildingsmayhavemorethanonekilowatt-hourmeter,dependinguponthenumberofoccupancies.从这一点开始，连接到每户公寓的出线都经过各自的电度表，然后再接小容量的断路装置和过流保护装置。分支电路面板一般安装在每个公寓。馈线导体将各个断路装置连接到分支电路面板上。商业及/或工业楼宇可能有不止一个千瓦时电表，视住户数目而定。3.2.3

CommercialandIndustrialInstallations

Theservicesizesvaryaccordingtothedemand.Theserviceisusuallyathree-phase,four-wiresystem.Theavailablevoltagesmaybe120/208Vor277/480V.Ifthesystemprovides277/480V,atransformermustbeinstalledinordertoobtain120V.Ifthebuildingcoversalargearea,itisrecommendedthattheservicebeinstallednearthecenterofthebuilding.Thisarrangementminimizeslinelossonfeederandbranch-circuitconductors.服务的大小根据需求而不同。该服务通常是三相四线制系统。可用电压为120/208v或277/480v。如果系统提供277/480v电压，则必须安装变压器以获得120V电压。如果建筑物占地面积较大，建议将服务安装在建筑物中心附近。这种布置将馈线和分支电路导体上的线路损耗降至最低。3.2.3

CommercialandIndustrialInstallations

Someutilitiessupplyathree-phase,three-wireorthree-phase,four-wiredeltasystem.Thecommonvoltagesthatmaybeobtainedfromthethree-wiredeltasystemare240V,440V,or550V.Withthisarrangement,atransformermustbeusedtoobtain120V.Theusualvoltagessuppliedfromthefour-wiredeltasystemare240V,threephasesand120V,singlephase.一些电力公司提供三相三线制或三相四线制delta系统。可以从三线三角系统中获得的常用电压为240V,440V或550V。在这种情况下，必须使用变压器来获得120V的电压。四线制三角系统通常提供的电压为三相240V和单相120V。3.2.3

CommercialandIndustrialInstallations

Manylargeconsumerspurchasetheelectricalenergyattheprimaryvoltage,andtransformersareinstalledontheirpremises.Three-phasevoltagesupto15kVareoftenused.许多大用户在一次电压下购买电能，变压器就安装在他们的房子里。通常使用15千伏以下的三相电压。3.2.3

CommercialandIndustrialInstallations

Theserviceforthistypeofinstallationgenerallyconsistsofmetalcubiclescalledasubstationunit.Thetransformersareeitherinstalledwithinthecubicleoradjacenttoit.Isolationswitchesofthedrawertypeareinstalledwithinthecubicle.Theseswitchesareusedtoisolatethemainswitchorcircuitbreakerfromthesupplyduringmaintenanceorrepair.这种类型的安装服务通常由称为变电站单元的金属隔间组成。变压器要么安装在隔间内，要么安装在隔间附近。抽屉式隔离开关安装在隔间内。这些开关用于在维护或维修期间将主开关或断路器与电源隔离。3.2.4

ConsumerLoopSystems

Althoughtheradialsystemofdistributionisprobablythemostcommonlyusedsystemoftransmittingpowerontheconsumer’sproperty,theloopsystemisalsoemployed.AblockdiagramofbothsystemisillustratedinFig.3.3(a)and3.3(b).Thereareseveralvariationsofthesesystemsinuseintheindustry,butthesystemsillustratedhereshowthebasicstructure.尽管放射式配电系统可能是用户财产上最常用的输电系统，但环网系统也被采用。两个系统的框图如图3.3(A)和3.3(b)所示。在工业中使用的这些系统有几种变体，但这里所示的系统显示了基本结构。3.2.4

ConsumerLoopSystems

Fig.3.3(b)Consumerloopdistributionsystem图3.3(b)消费者回路分配系统3.2.4

ConsumerLoopSystems

Wheninstallinganysystem,over-currentprotectionandgroundingmustbegivenprimaryconsideration.ElectricalpersonnelwhodesignandinstallthesesystemsmustcomplywiththeNECandlocalrequirements.Disconnectingmeansmaybeinstalledanywhereinthedistributionlooptoprovideforisolatingsections.在安装任何系统时，必须首先考虑过流保护和接地。设计和安装这些系统的电气人员必须符合NEC和当地的要求。断开装置可以安装在配电回路的任何地方，以提供隔离部分。3.2.5

SecondaryHigh-voltageDistributionLargeindustrialestablishmentsmayfinditmoreeconomicaltodistributepoweratvoltageshigherthan600V.Dependinguponthetypeofinstallationandtheloadrequirements,voltagesashighas2300Vmaybeused.Step-downtransformersareinstalledinstrategiclocationstoreducethevoltagetoapracticalworkingvalue.Adiagramofahigh-voltageradialsystemisshowninFig.3.4.大型工业机构可能会发现在高于600伏的电压下分配电力更经济。根据安装类型和负荷需求,可能需要2300V的电压。在关键位置安装降压变压器将电压降低到实际工作电压值。高压放射式接线系统示意图如图3.4所示。3.2.5

SecondaryHigh-voltageDistributionFig3.4Secondaryhigh-voltageradialdistributionsystem图3.4二次高压放射式接线配电系统3.2.5

SecondaryHigh-voltageDistributionSometimesthehigh-voltage(primary)systemmayberadial,andthelow-voltage(secondary)systemmaybeconnectedintoaloop.Anothermethodistohaveboththeprimariesandsecondariesconnectedtoformaloop.Fig.3.5(a)andFig.3.5(b)showthesemethods.有时高压(一次)系统可能放射式接线，低压(二次)系统可能连接成闭环。另一种方法是将主次线连接起来形成闭环。图3.5(a)和图3.5(b)显示了这些方法。3.2.6

SecondaryTiesLoopSystemItisfrequentlyconvenienttoconnectloadstothesecondaryconductorsatpointsbetweentransformers.Theseconductorsarecalledsecondaryties.Article450oftheNECgivesspecificrequirementsregardingtheconductorsizesandover-currentprotection.多数情况下从接入点点将负载连接到变压器之间也是很方便的。这些导线称为二次连接。NEC第450条对导体尺寸和过流保护给出了具体要求。3.2.6

SecondaryTiesLoopSystemFig3.5(a)Secondaryhigh-voltagedistributionsystem;high-voltageradical；low-voltageloop图3.5(a)二次高压配电系统;高压自由基；低压回路3.2.6

SecondaryTiesLoopSystemFig3.5(b)Consumerdistributionsystemwithhigh-voltageandlow-voltageloops图3.5(b)高压回路和低压回路的配电系统Introduction3.1DistributionSystemsStructure3.2LoadinDistributionSystem3.3DistributionNetworkAutomationSystem3.4目录3.3.1

StaticLoadModelsInthisandotherloadmodelsdescribedinthissection,在这个和本节中描述的其他负载模型中，3.3.1

StaticLoadModelsWherePandQareactiveandreactivecomponentsoftheloadwhenthebusvoltagemagnitudeisV.Thesubscriptoidentifiesthevaluesoftherespectivevariablesattheinitialoperatingcondition.式中，当母线电压幅值单位为V时，P和Q为负载的有功分量和无功分量，下标0表示初始运行条件下各变量的值。3.3.1

StaticLoadModelsTheparametersofthismodelaretheexponentsaandb.Withtheseexponentsequalto0,1，or2,themodelrepresentsconstantpower,constantcurrent,orconstantimpedancecharacteristics,respectively.Forcompositeloads,theirvaluesdependontheaggregatecharacteristicsofloadcomponents.该模型的参数为指数a和b，当指数分别为0、1和2时，该模型分别代表恒功率、恒电流和恒阻抗特性。对于综合负载，它们的值取决于荷载分量的总体特性。3.3.1

StaticLoadModelsTheexponenta(orb)isnearlyequaltotheslopedP/dV(ordQ/dV)atV=V0.Forcompositesystemloads,theexponentausuallyrangesbetween0.5and1.8;theexponentbistypicallybetween1.5and6.Asignificantcharacteristicoftheexponentbisthatitvariesasanonlinearfunctionofvoltage.Thisiscausedbymagneticsaturationindistributiontransformersandmotors.Athighervoltages,Qtendstobesignificantlyhigher.指数a(或b)几乎等于在V=V0时dP/dV(或dQ/dV)的斜率。对于复合系统负载，指数a通常在0.5到1.8之间;指数b通常在1.5到6之间。指数b的一个重要特征是它作为电压的非线性函数而变化。这是由配电变压器和电动机中的磁饱和引起的。在更高的电压下，Q趋于显著更高。3.3.1

StaticLoadModelsIntheabsenceofspecificinformation,themostcommonlyacceptedstaticloadmodelistorepresentactivepowerasconstantcurrent(i.e.,a=l)andreactivepowerasconstantimpedance(i.e.,b=2).在没有具体信息的情况下，最普遍接受的静态负载模型是将有功功率表示为恒流(即a=l)，无功功率表示为恒阻抗(即b=2)。Analternativemodelwhichhasbeenwidelyusedtorepresentthevoltagedependencyofloadsisthepolynomialmodel:另一种被广泛用于表示负载电压依赖性的模型是多项式模型:3.3.1

StaticLoadModelsThismodeliscommonlyreferredtoastheZIPmodel,asitiscomposedofconstantimpedance(Z),constantcurrent(I),andconstantpower(P)components.Theparametersofthemodelarethecoefficientsp1top3andq1toq3,whichdefinetheproportionofeachcomponent.该模型通常被称为ZIP模型，因为它由恒定阻抗(Z)，恒定电流(I)和恒定功率(P)组成。模型的参数为系数p1~p3和q1~q3，分别定义了各成分所占的比例。3.3.1

StaticLoadModelsThefrequencydependencyofloadcharacteristicsisusuallyrepresentedbymultiplyingtheexponentialmodelorthepolynomialmodelbyafactorasfollows:负荷特性的频率依赖性通常用指数模型或多项式模型乘以一个因子来表示，如下所示:3.3.1

StaticLoadModelsWhereΔfisthefrequencydeviation(f-f0).Typically,KPfrangesfrom0to3.0,andKqfrangesfrom-2.0to0.Thebusfrequencyfisusuallynotastatevariableinthesystemmodelusedforstabilityanalysis.Therefore,itisevaluatedbycomputingthetimederivativeofthebusvoltageangle.其中Δf为频率偏差(f-f0)。一般情况下，KPf的取值范围是0~3.0,Kqf的取值范围是-2.0~0。在用于稳定性分析的系统模型中，母线频率f通常不是状态变量。因此，通过计算母线电压角的时间导数来评估。3.3.1

StaticLoadModelsAcomprehensivestaticmodelwhichofferstheflexibilityofaccommodatingseveralformsofloadrepresentationisasfollows:一个全面的静态模型提供了灵活性，以适应几种形式的负载表示如下:Theexpressionforthereactivecomponentoftheloadhasasimilarstructure.Thereactivepowercompensationassociatedwiththeloadisrepresentedseparately.负载的无功分量的表达式具有类似的结构。与负荷相关的无功补偿分别表示。3.3.1

StaticLoadModelsThestaticmodelsgivenbyEquations3.1to3.6arenotrealisticatlowvoltages,andmayleadtocomputationalproblems.Therefore,stabilityprogramsusuallymakeprovisionsforswitchingtheloadcharacteristictotheconstantimpedancemodelwhenthebusvoltagefallsbelowaspecifiedvalue.式3.1至3.6给出的静态模型在低电压下不符合实际，可能导致计算问题。因此，稳定性程序通常规定，当母线电压低于规定值时，将负载特性切换到恒定阻抗模型。3.3.1

StaticLoadModelsIntheloadmodelusedintheEPRIExtendedTransient/MidtermStabilityProgram(ETMSP),theexponentsa1,a2,b1,andb2arevariedasafunctionofvoltagebelowathresholdvalueofbusvoltage,andtheconstantpowerandconstantcurrentcomponentsareswitchedtoconstantimpedancerepresentation.在EPRI扩展暂态/中长期稳定程序中的负荷模型中，当电压方程中的电压低于母线电压阈值时，通过改变变量a1、a2、b1、b2的值，恒功率和恒电流元件可以转为恒阻抗（模型）。3.3.2

DynamicLoadModelsTheresponseofmostcompositeloadstovoltageandfrequencychangesisfast,andthesteadystateoftheresponseisreachedveryquickly.Thisistrueatleastformodestamplitudesofvoltage/frequencychange.Theuseofstaticmodelsdescribedintheprevioussectionsisjustifiedinsuchcases.大多数复合负载对电压和频率变化的响应是快速的，并且很快达到稳态。至少这对电压/频率变化的振幅是正确的。在这种情况下，前面章节中描述的静态模型的使用是合理的。3.3.2

DynamicLoadModelsThereare,however,manycaseswhereitisnecessarytoaccountforthedynamicsofloadcomponents.Studiesofinterareaoscillations,voltagestability,andlong-termstabilityoftenrequireloaddynamicstobemodeled.Studyofsystemswithlargeconcentrationsofmotorsalsorequiresrepresentationofloaddynamics.然而，在许多情况下，有必要考虑负载元件的动态过程。区域间振荡、电压稳定性和长期稳定性的研究通常需要对负载动力学进行建模。研究大量电机集中的系统也需要用负载动力学表示。3.3.2

DynamicLoadModelsTypically,motorsconsume60to70%ofthetotalenergysuppliedbyapowersystem.Therefore,thedynamicsattributabletomotorsareusuallythemostsignificantaspectsofdynamiccharacteristicsofsystemloads.通常情况下，电机消耗电力系统提供的总能量的60-70%。因此，电机的动态特性通常是系统负载动态特性中最重要的方面。Otherdynamicaspectsofloadcomponentsthatrequireconsiderationinstabilitystudiesincludethefollowing:在稳定性研究中需要考虑的负荷的其他动态方面包括:3.3.2

DynamicLoadModels(a)Extinctionofdischargelampsbelowacertainvoltageandtheirrestartwhenthevoltagerecovers.Dischargelampsincludemercuryvapour,sodiumvapour,andfluorescentlamps.Theseextinguishatvoltagesintherangeof0.7to0.8pu.Whenthevoltagerecovers,theyrestartafterIor2secondsdelay.(a)低于一定电压的放电灯熄灭，电压恢复后重新启动。放电灯包括汞蒸气、钠蒸气和荧光灯。这些在0.7至0.8普的电压范围内熄灭。当电压恢复后，它们在1或2秒后重新启动。3.3.2

DynamicLoadModels(b)Operationofprotectiverelays,suchasthermalandovercurrentrelays.Manyindustrialmotorshavestarterswithelectromagneticallyheldcontactors.Thesedropsopenatvoltagesintherangeof0.55to0.75pu;thedropouttimeisontheorderofafewcycles.Smallmotorsonrefrigeratorsandairconditionershaveonlythermaloverloadprotections,whichtypicallytripinabout10to30seconds.(b)保护继电器的操作，如热继电器和过电流继电器。许多工业电机的起动器都带有电磁接触器。他们在0.55至0.75pu的电压范围内跳开;跳开时间大约是几个周期。冰箱和空调上的小电机只有热过载保护，通常在10到30秒内跳闸。3.3.2

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