电气工程及其自动化专业英语 课件 -Chapter 2 Transmission system

目录Introduction2.1TransmissionLines2.2Transformers2.3ExtraHighVoltage(EHV)Transmission2.4Chapter2Transmissionsystemeactivepower无功功率

overheadline架空线leakagecurrent泄漏电流alternatingvoltages交流电压capacitance[kə'pæsitəns]n.电容，电流容量parameter[pə'ræmitə]n.参数，系数，参量insulate['insjuleit,'insə-]vt.隔离，使绝缘impregnate['impreɡneit,im'preɡ-,im'preɡnit,-neit]adj.浸渍的，浸染的sinusoidal[,sinə'sɔidl]adj.正弦曲线的shuntadmittance并联导纳propagationconstant传播常数Shunt（）mayincreasethesettlingtime.capacitancereducesinductorelectricreactorABCD提交单选题1分attenuationconstant衰减常数incidentvoltage入射电压exponential[,ekspəu'nenʃəl]adj.指数的tap[tæp]n.抽头compensate['kɔmpenseit]vt.补偿tap-changing['tæp'tʃeindʒiŋ]n.抽头切换distributiontransformers输电变压器autotransformer[,ɔ:təutræns'fɔ:mə]n.自耦变压器magneticcoupling磁力耦合transformationratio变比overload[,əuvə'ləud,'əuvələud]n.过载，超负荷()facetocustomersdirectly,itsoperationstateistheimportantcomponentofsafeeconomicaloperationofthewholedistributionnetwork.ACtransformerammeterDistribution

transformersVoltmeterABCD提交单选题1分saturation[,sætʃə'reiʃən]n.饱和，磁化饱和turnsratio匝数比deviation[,di:vi'eiʃən]n.偏差，误差irrespectiveof不考虑fictitious[fik'tiʃəs]adj.虚构的，假想的transient['trænziənt]adj.暂态的symmetrical[si'metrikəl]adj.匀称的，对称的transferadmittance转移导纳tremendous[tri'mendəs]adj.巨大的infrastructure['infrə,strʌktʃə]n.基础设施transmissiongrid输电网Impedancewillreflectbackasthesquareofthe（）.acceleratedspeedArmatureWindingnumberofturnsturnsratioABCD提交单选题1分generatingplants发电厂optimize['ɔptimaiz]vt.使最优化reliability[ri,laiə'biləti]n.可靠性coordinate[kəu'ɔ:dinit,kəu'ɔ:dineit]vi.协调alleviate[ə'li:vieit]vt.减轻，缓和complementary[,kɔmpli'mentəri]adj.补足的，补偿的innovation[,inəu'veiʃən]n.创新commissioned[kə'miʃənd]adj.受委任的，被任命的synchronize['siŋkrənaiz]vt.使同步backbonegrids主干网demonstration[,demən'streiʃən]n.示范，证明Duringthesameperiod,theworldwasthrustintothenuclearerawithbothitsdestructivedevicesanditspower-（）.hydropowerstationgeneratingplantsnuclearpowerstationdynamoABCD提交单选题1分geographic[dʒiə'græfik]adj.地理的，地理学的substation['sʌbsteiʃən]n.变电站feasibility[,fi:zə'biliti]n.可行性preliminary[pri'liminəri]adj.初步的，预备的facilitate[fə'siliteit]vt.促进，帮助（）locatingisanimportantpartofpowersystemplanning.transformerconvertorstationSubstationcontrolcenterABCD提交单选题1分目录Introduction2.1TransmissionLines2.2Transformers2.3ExtraHighVoltage(EHV)Transmission2.4Electricalpoweristransmittedfromgeneratingstationstoconsumersthroughoverheadlinesandcables.电能通过架空线路和电缆从发电厂输送给电力用户。2.1IntroductionOverheadlinesareusedforlongdistancesinopencountryandruralareas.Whereascablesareusedforundergroundtransmissioninurbanareasandforunderwatercrossings.Forthesamerating,cablesare10to15timesmoreexpensivethanoverheadlinesandtheyarethereforeonlyusedinspecialsituationswhereoverheadlinescannotbeused;thedistancesinsuchapplicationareshort.

架空线路用于旷野和农村地区的长距离线路。而电缆则用于城市地区的地下和从水下敷设。相同输送容量下，电缆的投资比架空线路贵10到15倍，因此它们只用于不能使用架空线路的特殊情况;这些应用中的距离都很短。Introduction2.1TransmissionLines2.2Transformers2.3ExtraHighVoltage(EHV)Transmission2.4目录2.2.1OverheadlinesAtransmissionlineischaracterizedbyfourparameters:seriesresistanceRduetotheconductorresistivety,shuntconductanceGduetoleakagecurrentsbetweenthephaseandground,seriesinductanceLduetomagneticfieldsurroundingtheconductor,andshuntcapacitanceCduetotheelectricfieldbetweenconductors.传输线的特征有四个参数:导体电阻率引起的串联电阻R，相与地之间漏电流引起的并联电导G，导体周围磁场引起的串联电感L，导体之间电场引起的并联电容C。2.2.1OverheadlinesDetailedderivationsfromfirstprinciplesforthelineparameterscanbefoundinstandardbooksonpowersystems.Here,wewillbrieflysummarizesalientpointsrelatingtolineparameters.线路参数的详细推导的原理可以在电力系统的标准书籍中找到。在这里，我们将简要总结与线路参数有关的要点。2.2.1OverheadlinesSeriesresistanceR.Theresistancesoflinesaccountingforstandingandskineffectaredeterminedfrommanufacturers’tables.ShuntconductanceG.Theshuntconductancerepresentslossesduetoleakagecurrentsalonginsulatorstringsandcorona.Inpowerlines,itseffectissmallandusuallyneglected.串联电阻R：线路的电阻根据制造商的目录确定。并联电导G：并联电导表示由于绝缘子串和电晕上的泄漏电流而造成的损耗。在输电线中，它的影响很小，通常被忽略。2.2.1OverheadlinesSeriesinductanceL.Thelineinductancedependsonthepartialfluxlinkageswithintheconductorcrosssectionandexternalfluxlinkages.Foroverheadlines,theinductancesofthethreephasesaredifferentfromeachotherunlesstheconductorshaveequilateralspacing,ageometrynotusuallyadoptedinpractice.串联电感L：线路电感取决于导体截面内的部分磁链和外部磁链。对于架空线路，除非导体间距相等，否则三相间电感互不相同，但在实际中通常不采用这种（等边三角形）结构。2.2.1OverheadlinesTheinductancesofthethreephaseswithnon-equilateralspacingcanbeequalizedbytransposingthelinesinsuchawaythateachphaseoccupiessuccessivelyallthreepossiblepositions.通过调换线路，使每个相位依次占据所有三个可能的位置，可以使具有非等边间距的三个相位的电感相等。2.2.1OverheadlinesForatransposedthree-phaseline,theinductanceperphaseis

Intheaboveequation，Dsistheselfgeometricmeandistance,takingintoaccounttheconductorcomposition,stranding,andbundling;itisalsocalledthegeometricmeanradius.AndDeqisthegeometricmeanofthedistancesbetweentheconductorsofthethreea,b,andc:对于转置的三相线路，每相电感为上式中，Ds为自身几何平均距离，考虑到导体的组成、绞合和捆扎;它也被称为几何平均半径。Deq是abc三个导体之间距离的几何平均值2.2.1OverheadlinesThepotentialdifferencebetweentheconductorsofatransmissionlinecausestheconductorstobecharged;thechargeperunitofpotentialdifferenceisthecapacitancebetweenconductors.Whenalternatingvoltagesareappliedtothecapacitances.当对电容施加交流电压时，传输线导体之间的电位差使导体带电;单位电势差的电荷就是导体间的电容。备注：电容是电荷与电势差之间的比值,用来衡量电路存储电荷的能力。2.2.2UndergroundcablesUndergroundcableshavethesamebasicparametersasoverheadlines:seriesresistanceandinductance;shuntcapacitanceandconductance.However,thevaluesoftheparametersandhencethecharacteristicofcablesdiffersignificantlyformthoseofoverheadlinesforthefollowingreasons:地下电缆具有与架空线路相同的基本参数:串联电阻和电感,并联电容和电导。但由于以下原因，电缆的参数值和特性与架空线路有很大的不同:2.2.2Undergroundcables（1） Theconductorsinacablearemuchclosertoeachotherthantheconductorsofoverheadlines.（2） Theconductorsinacablearesurroundedbymetallicbodiessuchasshield,leadoraluminumsheets,andsteelpipes.（3） Theinsulatingmaterialbetweenconductorsinacableisusuallyimpregnatedpaper,low-viscosityoil,oraninertgas.(1)电缆导体之间的距离比架空线路的导体之间的距离要近得多。(2)电缆导体周围有金属体，如屏蔽板、铅板或铝板、钢管等。(3)电缆导体之间的绝缘材料通常是浸渍纸、低粘度油或惰性气体。2.2.2UndergroundcablesIntheprevioussection,weidentifiedtheparametersofatransmissionlineperunitlength.Thesearedistributedparameters;thatis,theeffectsrepresentedbytheparametersaredistributedthroughoutthelengthoftheline.在上一节中，我们确定了单位长度传输线的参数。这些是分布参数;也就是说，由参数表现的效应分布在整个线的长度上。2.2.2UndergroundcablesIfthelineisassumedtransposed,wecananalyzethelineperformanceonaper-phasebasis.Fig.2.1showstherelationshipbetweencurrentandvoltagealongonephaseofthelineintermsofthedistributedparameters,with如果假设线路经过完整的换位，我们可以按相分析线路的性能。图2.1给出了沿线路某相电流与电压的分布参数关系，其中……Fig.2.1Voltageandcurrentrelationshipofadistributedparameterline2.Undergroundcableshavethesamebasicparametersasoverheadlines:seriesresistanceandinductance;shuntcapacitanceandconductance.地下电缆具有与架空线路相同的基本参数:串联电阻和电感,并联电容和电导。Introduction2.1TransmissionLines2.2Transformers2.3ExtraHighVoltage(EHV)Transmission2.4目录2.3.1IntroductionAtransformerisadeviceusedtoconvertvoltagelevelsinanACcircuit.Theyhavenumeroususesinpowersystems.Tobegin,itismoreefficienttotransmitpowerathighvoltagesandlowcurrentthanlowvoltageandhighcurrent.Conversely,lowervoltagesaresaferandmoreeconomicforenduse.变压器是一种在交流电路中用来转换电压等级的装置。它们在电力系统中有许多用途。首先，在高电压和小电流下传输功率比在低电压和大电流下传输功率更有效。反过来说，较低的电压更安全，更经济的最终用途。2.3.1IntroductionThus,transformersareusedtostep-upvoltagesfromthegeneratorsandthenusedtostep-downthevoltageforenduse.Anotherwideuseoftransformersisforinstrumentationsothatsensitiveequipmentcanbeisolatedfromthehighvoltagesandcurrentsofthetransmissionsystem.Transformersmayalsobeusedasmeansofcontrollingrealpowerflowbyphase-shifting.因此，变压器用于从发电机升压电压，然后用于降压电压，以供最终使用。变压器的另一个广泛用途是用于仪器仪表，以便将灵敏的设备与传输系统的高压和高压电流隔离开来。变压器也可用作通过移相控制实际功率流的手段。2.3.1IntroductionTransformersenableutilizationofdifferentvoltagelevelsacrossthesystem.Fromtheviewpointsofefficiencyandpower-transfercapability,thetransmissionvoltageshavetobehigh,butitisnotpracticallyfeasibletogenerateandconsumepoweratthesevoltages.变压器使在系统中利用不同的电压等级成为可能。从效率和输电能力的角度考虑，输电电压必须高，但在这样的电压下发电和用电是不现实的。2.3.1IntroductionInmodernelectricpowersystems,thetransmittedpowerundergoesfourtofivevoltagetransformationsbetweenthegeneratorsandtheultimateconsumers.Consequently,thetotalMVAratingofallthetransformersinapowersystemisaboutfivetimesthetotalMVAratingofallthegenerators.在现代电力系统中，传输的电力在发电机和最终用户之间要经历4到5次电压转换。因此，电力系统中所有变压器的总额定值视在功率大约是所有发电机的总额定视在功率的5倍。2.3.1IntroductionInadditiontovoltagetransformation,transformersareoftenusedforcontrolofvoltageandreactivepowerflow.Therefore,practicallyalltransformersusedforbulkpowertransmissionandmanydistributiontransformershavetapsinoneormorewindingsforchangingtheturnsratio.除了电压变换，变压器经常用于控制电压和无功潮流。因此，几乎所有用于大功率传输的变压器和许多配电变压器都有一个或多个分接头来改变匝数比。2.3.1IntroductionFromthepowersystemviewpoint,changingtheratiooftransformationisrequiredtocompensateforvariationsinsystemvoltages.Twotypesoftap-changingfacilitiesareprovided:off-loadtapchangingandunder­loadtapchanging(ULTC).Theoff-loadtap-changingfacilitiesrequirethetransformertobede-energizedfortapchanging;theyareusedwhentheratiowillneedtobechangedonlytomeetlong-termvariationsduetoloadgrowth,systemexpansion,orseasonalchanges.从电力系统的角度来看，需要改变变比来补偿系统电压的变化。提供两种类型的分接头转换设施:无载调压分接头转换和有载调压分接头转换(ULTC)。无载分接设施要求变压器断电进行分接;只有当由于负荷增长、系统扩展或季节变化而需要改变比例以满足长期变化时，（才会）使用它们。2.3.1IntroductionTheULTCisusedwhenthechangesinrationeedtobefrequent;forexample,totakecareofdailyvariationsinsystemconditions.Thetapsnormallyallowtheratiotovaryintherangeof±10%to±15%.当变比变化需求频繁时，使用ULTC;例如，考虑到系统运行条件的日常变化。抽头通常允许该变比在±10%到±15%的范围内变化。2.3.1IntroductionTransformersmaybeeitherthree-phaseunitsorthreesingle-phaseunits.ThelattertypeofconstructionisnormallyusedforlargeEHVtransformersandfordistributiontransformers.LargeEHVtransformersareofsingle-phasedesignduetothecostofspare,insulationrequirements,andshippingconsiderations.Thedistributionsystemsservesingle-phaseloadsandaresuppliedbysingle-phasetransformers.变压器可以是一体的三相变压器或者由三个单相变压器组成三相的。后一种结构通常用于大型超高压变压器和配电变压器。由于备件成本、绝缘要求和运输考虑，大型超高压变压器采用单相设计。配电系统用于单相负载，由单相变压器供电。2.3.1IntroductionWhenthevoltagetransformationratioissmall,autotransformersarenormallyused.Theprimaryandsecondarywindingsofautotransformersareinterconnectedsothatthepowertobetransformedbymagneticcouplingisonlyaportionofthetotalpowertransmittedthroughthetransformer.Thereisthusinherentmetallicconnectionbetweentheprimarysideandsecondarysidecircuits;thisisunliketheconventionaltwo-windingtransformerwhichisolatesthetwocircuits.当电压变比较小时，通常采用自耦变压器。自耦变压器的初级绕组和次级绕组是相互连接的，因此通过磁耦合转换的功率只是通过变压器传输的总功率的一部分。因此，在初级侧和次级侧电路之间存在固有的金属连接;这与传统的双绕组变压器不同，它的两个绕组电路是隔离的。2.3.1IntroductionAutotransformersareusuallyYconnected,withneutralssolidlygroundedtominimizethepropagationofdisturbancesoccurringononesideintotheotherside.Itisacommonpracticetoaddalow-capacitydelta-connectedtertiarywinding.自耦变压器通常是Y型连接，中性点牢固接地，以尽量减少一侧发生的干扰传播到另一侧。通常的做法是增加一个小容量的三角连接的第三绕组。2.3.1IntroductionThetertiarywindingprovidesapathforthirdharmoniccurrents,therebyreducingtheirflowonthenetwork.Italsoassistsinstabilizingtheneutral.Reactivecompensationisoftenprovidedthroughuseofswitchedreactorsandcapacitorsonatertiarybus.第三绕组为三次谐波电流提供了通道，从而减少了它们在网络上的流量。它还有助于稳定中性点电位。无功补偿通常通过在第三母线上使用投切电抗器和电容器来提供。2.3.1IntroductionAscomparedtotheconventionaltwo-windingtransformer,theautotransformerhasadvantagesoflowercost,higherefficiency,andbetterregulation.Theseadvantagesbecomelesssignificantasthetransformationratioincreases;hence,autotransformersareusedforlowtransformationratios(forexample,500/230kV).

相比传统的双绕组变压器，自耦变压器具有成本低、效率高、调节性能好等优点。这些优势在高变压系数的时候并不是很明显，因此，自耦变压器用于低变换比(例如，500/230kV)。2.3.1IntroductionIninterconnectedsystems,itsometimesbecomesnecessarytomakeelectricalconnectionsthatformloopcircuitsthroughoneormorepowersystems.Tocontrolthecirculationofpowerandpreventoverloadingcertainlines,itisusuallynecessaryinsuchsituationstousephase-angletransformers.在互联系统中，有时需要通过一个或多个电力系统进行电气连接形成环路。为了控制电力的循环和防止某些线路过载，在这种情况下通常需要使用移相变压器。2.3.1IntroductionOftenitisnecessarytovarytheextentofphaseshifttosuitchangingsystemconditions;thisrequiresprovisionofon­loadphase-shiftingcapability.Voltagetransformationmayalsoberequiredinadditiontophaseshift.通常需要改变相角差以适应不断变化的系统条件;这需要提供有载移相能力。除相移外，还可能需要电压变换。Introduction2.1TransmissionLines2.2Transformers2.3ExtraHighVoltage(EHV)Transmission2.4目录2.4.1IntroductionAttheendof2005theinstalledgenerationcapacityof500GWmakesChinathesecondhighestintheelectricityproductionintheworld,AsChinaisbeingtransformedintothemanufacturingcentreoftheworld,andtheincreaseofelectricitydemandistremendous.2005年底，中国发电装机容量达到500GW，成为世界发电量第二大的国家。中国正在变成世界制造业中心并且电力需求迅速增加。2.4.1IntroductionNewelectricenergyinfrastructureisrequiredtotransferbulkelectricityenergyoveraverylongdistance.Althoughthe500kVACand500-kVDCtransmissionsystemsareexisting,suchtransmissionnetworksarestillconsideredtobeinadequateforbulkelectricityenergytransmission.

新的电力能源基础设施需要在很远的距离上传输大量电能。虽然已有500千伏交流和500千伏直流输电系统，但这种输电网络仍被认为不足以满足大容量电能传输的需要。2.4.1IntroductionThecontinuousadvancesinelectricpowertransmissiontechnologymadeitpossibletotransferbulkelectricenergyoverlongerandlongerdistances.Withthedevelopmentoflargescaletransmissionsystems,voltagelevelshavebeenincreasedcontinuouslytoachievegreatereconomiesofscale.电力传输技术的不断进步使越来越远距离的大量电能传输成为可能。随着大型输电系统的规模的扩展，电压等级不断提高，以实现更大的规模经济。2.4.1IntroductionThehighestvoltagelevelnowinpracticaloperationis765kV.Thenextvoltagelevelis1000kVorover.Basicallyhighvoltage(HV)transmissionlevelsinclude100(110),138,161,230(220)kV,extrahighvoltagelevels(EHV)include345(330),400,500and765(750)kV,andultrahighvoltage(UHV)levelsareACvoltageshigherthan765kVandDCvoltageshigherthan600kV.目前实际运行的最高电压等级为765千伏。下一个电压等级是1000千伏或更高。高压(HV)等级主要包括100(110)、138、161、230(220)kV，特高压(EHV)等级包括345(330)、400、500和765(750)kV，超高压(UHV)等级是交流电压高于765kV和直流电压高于600kV。2.4.1IntroductionTheultrohighvoltagegridbeingconsideredinChinaisthetransmissiongridwithvoltageshigherthan750kV.Itismainlysuitablefortransferringbulkelectricityenergyoveraverylongdistance.中国所考虑的特高压电网是指电压高于750kV的输电网。主要适用于远距离输送大量电能。2.4.1IntroductionPowerindustryindevelopedcountrieswasdevelopingveryquicklybetweenthelater1960s'andtheearly1970s',ItwasrecognizedthatahigherVoltagegridshouldbeintroducedwhenthecapacityofpowersystemisdoubled.Forthisreason,theresearchonsuperhighvoltagetransmissiongridbecamemoreimportant.20世纪60年代末至70年代初，发达国家的电力工业发展迅速，人们认识到，当电力系统容量增加一倍时，就应该引入高压电网。因此，对超高压输电网的研究就显得尤为重要。2.4.1IntroductionManycountries,suchastheUSA,Russia,Italy,France,JapanandSweden,begantomaketheirdesignandplanningofdevelopingultrohighvoltagegridatthattime.Howevertheseprojectswerenotcompletedbecauseofthepoliticalandeconomicfactors.与此同时，美国、俄罗斯、意大利、法国、日本、瑞典等国家也开始对发展特高压电网进行设计和规划。然而，由于政治和经济因素，这些项目没有完成。2.4.1IntroductionTheresearchprojectaboutultrohighvoltagegridinChinahasbeenconductedsince1986.Buttherearefewerprojectsonengineeringapplicationoronatrialbasis.中国特高压电网的研究项目始于1986年。但在工程应用或试验基础上的项目较少。2.4.1IntroductionAtpresent,withthedevelopmentofnationaleconomy,theelectricitydemandhasincreasedveryquickly.Notingthefactthatthereareverylongdistancesbetweenenergybasesandmajorloadcenters.Therefore,itisnecessarytoconstructthenationalgridtotransferpowerfromtheenergybasestothemajorloadcenters.目前，随着国民经济的发展，电力需求增长十分迅速。注意到能源基地和主要负荷中心之间的距离非常远。因此，有必要建设国家电网，将电力从能源基地输送到各大负荷中心。2.4.1IntroductionInordertomeettheneedofsocietydevelopment,theNationalGridCorporationhasbeenresponsibleforthedesignandplanningofconstructionofthesuperhighvoltagepowergrid.为了适应社会发展的需要，国家电网公司负责超高压电网的设计和规划建设。2.4.2EHVTransmissioninChinaIn2004,theelectricityshortageoccurredin24provincesinChina,amongwhichZhejiang,JiangsuandFujianaswerethemostseriousones.Theshortagein2004wasestimatedataround35GW.Oneofthereasonsisthattherewereblindinvestmentsinpowerplantswhilethereisalackofinvestmentsintransmissiongrid.2004年，全国24个省份发生了电力短缺，其中浙江、江苏和福建是最严重的。2004年的短缺估计约为35吉瓦。原因之一是电厂盲目投资，输电网投资不足。2.4.2EHVTransmissioninChinaAseriesofenergypoliciesforsolvingtheenergyproblemsinthedevelopmentofcoalandelectricityinChinahavebeenissuedbyChineseGovernment.Chinahasavastterritory.Itisknownthattherearemoreresourcesinhydroandcoal,butlessinoilandgas.HydroresourcesandcoalreservesarethemostimportantenergyresourcesinChina.Howeverthedistributionofelectricityenergysourcesandthatofelectricitydemandareseriouslyunbalanced.为解决中国煤电发展中的能源问题，中国政府出台了一系列能源政策。中国幅员辽阔。众所周知，水力和煤炭资源较多，而石油和天然气资源较少。水力资源和煤炭储量是中国最重要的能源资源。然而，电力能源分布与电力需求分布严重不平衡。2.4.2EHVTransmissioninChinaNearlytwothirdsofhydroresourcesaredistributedinthesouthwestandwestofChina,includingSichuan,YunnanandTibetprovinces.TwothirdsofthecoalreservesaredistributedinthenorthwestandnorthofChina,includingShanxi,XinjiangandInnerMongoliaprovinces.中国近三分之二的水力资源分布在西南和西部，包括四川、云南和西藏等省。三分之二的煤炭储量分布在中国的西北和北部，包括山西、新疆和内蒙古。2.4.2EHVTransmissioninChinaOntheotherhand,twothirdsofelectricityloadsweremainlyintheeastareasofChinawherethereisalackofelectricityenergysources.Thedistancebetweentheareasofenergyresourcesandenergydemandisverylong,say500km-1500km.另一方面，三分之二的电力负荷主要集中在电力能源匮乏的中国东部地区。能源资源区和能源需求区之间的距离很远，比如500公里到1500公里。2.4.2EHVTransmissioninChinaConsideringthereasonsmentionedabove,ahigherrequirementforthedevelopmentofanelectricitygridisbroughtforward.Accordingtothepresentplanning,about120millionKWcouldbesenttonorthChina,eastChinaandcentralChinafromthecoalbasesinthenorthwestandnorthChina.考虑到上述原因，对电网的发展提出了更高的要求。根据目前的规划，西北和华北的煤炭基地可向华北、华东和华中地区输送约1.2亿千瓦的电力。2.4.2EHVTransmissioninChinaThedistancesbetweenthemareabout500-1500km,whichisevenmorereasonabletransportationdistanceforACsuperhighvoltagegridthanthatfortransportationofenergyresourcesbytrainsincetheresearchresultshaveshownthatitismuchmoreeconomictotransfertheelectricitythantotransportcoalwithin1500km.它们之间的距离约为500-1500公里，这是交流超高压电网比火车运输能源更合理的运输距离，因为研究结果表明，在1500公里内转移电力比运输煤炭更经济。2.4.2EHVTransmissioninChinaAttheendof2005theinstalledgenerationcapacityof500GWmakesChinathesecondhighestintheelectricityproductionintheworld.AsChinaisbeingtransformedintothemanufacturingcentreoftheworld,theincreaseofelectricitydemandistremendous.2005年底，中国发电装机容量达500吉瓦，成为世界上发电量第二高的国家。随着中国转型为世界制造业中心，电力需求的增长是巨大的。2.4.2EHVTransmissioninChinaNewelectricenergyinfrastructureisrequiredtotransferbulkelectricityenergyoveraverylongdistance.Althoughthe500kVACand500kVDCtransmissionsystemsareexisting,suchtransmissionnetworksarestillconsideredtobeinadequateforbulkelectricityenergytransmission.新的电力能源基础设施需要在很长的距离上传输大量电能。虽然已有500千伏交流和500千伏直流输电系统，但这种输电网络仍被认为不足以满足大容量电能的传输。2.4.2EHVTransmissioninChinaItisestimatedthattheinstalledgenerationcapabilitywillbe1000GWin2020.IthasbeenrecognizedthatlargeamountsofhydroandcoalresourcesaredistributedinthesouthwestandnorthwestofChina.Henceinordertomeettheenergyconsumptionmoregeneratingplantswillbeconstructedintheseregionsby2020.预计到2020年装机容量将达到1000吉瓦。中国的西南和西北地区分布着大量的水电和煤炭资源。因此，为了满足能源消耗，到2020年，这些地区将建设更多的发电厂。2.4.2EHVTransmissioninChinaOntheotherhand,loadcentersaresituatedintheeastcostalareasofChina.Accordingtotheexperienceofinternationalpowerindustry,whenthecapacityofpowergridisexpandedby4times,ahighervoltagelevelshouldbeintroduced.Thecurrent500kVpowergridhasahistoryof23yearswhiletheinstalledgenerationcapabilityin2004isaround6timesthatoftheinstalledgenerationcapabilityin1982.另一方面，负荷中心位于中国东部沿海地区。根据国际电力行业的经验，当电网容量扩大4倍时，应引入更高的电压等级。目前500kV电网已有23年的历史，2004年的装机容量是1982年装机容量的6倍左右。2.4.2EHVTransmissioninChinaPresentlythetransmissionofelectricityacrossprovincialpowernetworksismainlybasedonthe500kVACand±500kVDCtransmissiongrids.Ithasbeenfoundthatsuchtransmissionpowergridscannotmeetthebulkpowertransmissionrequirementsin2020.Clearlyinthissituationpowergridsofhighervoltagelevelsarerequired.目前各省电网的电力传输主要以500kv交流和±500kv直流输电网为主。研究发现，这样的输电电网已不能满足2020年大容量输电的要求。显然，在这种情况下，需要更高电压水平的电网。2.4.2EHVTransmissioninChinaLongdistancebulkpowertransmissioncansatisfyfuturepowergrowth,secureenergysupply,andoptimizeenergyresourcesallocation.Furthermore,overallsocialbenefitswillbeimprovedbyenhancingpowergridsafetyandreliability,savingright-of-way,coordinatingthedevelopmentofpowerplantsandgrid,alleviatingcoaltransportationpressureandboostingtheharmoniousdevelopmentofregionaleconomy.远距离大容量输电可以满足未来电力增长，保障能源供应，优化能源配置。提高电网安全可靠性，节约路权，促进电厂电网协调发展，缓解煤炭运输压力，促进区域经济协调发展，从而提高整体社会效益。2.4.2EHVTransmissioninChina1000kVACand±800kVDCtransmissiongridshavedifferentfeatures.Theyarecomplementary.Thenaturalsinglecircuitcapacityof1000kVACtransmissionlineisabout5GW,andthatof±800kVDCtransmissionlineisatmost6.4GW.1000kV交流输电网和±800kv直流输电网具有不同的特点。它们是互补的。1000kV交流输电线路自然单回路容量约5GW，±800kV直流输电线路自然单回路容量不超过6.4GW。2.4.2EHVTransmissioninChinaThetransmissioncapacityofDCtransmissionlinedependsonthepowersystemconnection,restrictedbymaximumstabilitylimit.Itscapacityshouldbeupliftedgradually.Incontrast,thetransmissioncapacityofDCtransmissionlinecouldachievethedesignpowercapacitylevelassoonassupplysourceisavailable.直流输电线路的传输能力取决于电力系统的连接方式，受最大稳定极限的制约。它的能力应该逐步提高。而直流输电线路只要有供电源，输电容量就能达到设计功率容量水平。2.4.2EHVTransmissioninChinaThereasonabletransmissiondistanceof1000kVACtransmissionlineis1000-2000km.Ontheotherhand,±800kVDCtransmissionisthemosteconomicwayoflongdistancepowertransmissionwhentransmissiondistanceislargerthan1500km.1000千伏交流输电线路合理的传输距离为1000-2000公里。另一方面，当传输距离超过1500公里时，±800千伏（特高压）直流输电系统是长距离输电最经济的方式。2.4.2EHVTransmissioninChina1000kVACtransmissiongrid,whichhasgeneralfeaturesofACtransmissiongrid,canformasuperbackbonegridofanationalpowersystem.±800kVDCtransmission,"directsuperhighway",whichiscomplementarytoACtransmissiongrid,canbeusedtotransmissionbulkpowerfromlargepowergeneratingbasestolargeloadcentresoverlongdistances.1000kV交流输电网具有交流输电网的一般特征，可构成国家电力系统的超级骨干电网。±800kV直流输电，与交流输电网互补的“直达超高速公路”，可远距离将大型发电基地的大宗电力输送到大型负荷中心。2.4.2EHVTransmissioninChinaHowever,±800kVDCtransmissionwillnotbesuitableforforminganationalbackbonehighvoltagepowergridduetothelimitationofinterconnection.但是，±800kV直流输电由于互联的限制，将不适合形成国家骨干高压电网。2.4.3FutureofEHVTransmissionGridGridinChinaBasedonthetechnicalinnovationandupgradingofthecurrentgrid,asbeingplanned,theStateGridCorporationislikelytoconstructthenationalsuperhighvoltagegrid,realizingthecoordinateddevelopmentofthegridseparatedintodifferentvoltagelevels,optimizingtheutilizationofenergysourceswithinlargerareas,providingsafety,economicandhighqualityelectricpowerservices,meetingtherequirementsofeconomyandsocietydevelopment.在对现有电网进行技术创新和升级改造的基础上，国家电网公司有可能按照规划建设国家超高压电网，实现不同电压等级电网的协调发展，在更大范围内优化能源利用，提供安全、经济、优质的电力服务，满足经济社会发展的要求。2.4.3FutureofEHVTransmissionGridGridinChinaAccordingtothestrategicplanningofStateGridCo.,thenationalsuperhighvoltagegrid,whichcoversthemajorityareasofChina,shouldbeoperatedanddispatchedthroughaunitednationalcontrolcentre.ThenationalgridismainlybaseduponACinterconnectednetworkswiththeassistanceofDCinterconnectednetworks.根据现有国家电网公司的战略规划，覆盖中国大部分地区的国家超高压电网应通过一个国家统一控制中心进行运营和调度。国家电网以交流互联为主，辅以直流互联。2.4.3FutureofEHVTransmissionGridGridinChinaThebackbonegridwillbeinterconnectedby1000kVACtransmissionwiththeassistanceof±800kVDCtransmission.Thenorthwestpowergridwillbeinterconnectedby750kVACtransmission.Thefirst750kVACtransmissionlinewithatotallengthof140kmwascommissionedinSeptember2005.主干网将通过1000千伏交流输电和±800千伏直流输电相互连接。西北电网将通过750千伏交流输电实现互联。首条全长140公里的750千伏交流输电线路于2005年9月投运。2.4.3FutureofEHVTransmissionGridGridinChinaAccordingtothedesignandplanningofthenationalsuperhighvoltagegrid,twolargecapacitytransmissionchannelsshouldbeconstructed.Oneisthenorth-southchannelfromnorthviamiddletoeast,formingahugeUHVACsynchronizingpowergrid.Theotheristhewest-eastchannelfr