变压器电力英语.ppt

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1、电力英语阅读任惠华北电力大学电力工程系（保定）7/30/20211HUIREN@NCEPUDistanceRelay距离保护UndervoltageRelay低电压保护OvervoltageRelay过电压保护BlockingRelay闭锁继电器PhaseAngleorOutofStepRelay失步保护FrequencyRelay频率继电器DirectionalPowerRelay方向功率继电器InstantaneousOvercurrentRelay瞬时过流保护DifferentialRelay差动保护7/30/20212HUIR

2、EN@NCEPUGroundingSystemFormerly,manypowersystemswereungroundedsystemsusingdelta-deltatransformers.Ungroundedsystemssufferformseveralproblems,includingtransientovervoltagesthatnecessitatetheuseoftwosurgearrestersforasingle-phasetransformer(oneoneachsideofthewinding),andt

3、roublewithrapid,automaticclearingoftheverycommonphasetogroundshortcircuit.以前，许多电力系统采用角型接线变压器，为不接地系统。不接地系统会带来很多严重的问题，包括暂态过电压，因此，即使是单相变压器，也需要分别在原边和副边绕组各安装一个避雷器。而且对于非常常见的相接地故障的快速自动切除非常困难。7/30/20213HUIREN@NCEPUAnungroundedsystemisconnectedtogroundonlybystraycapacitances,soa

4、singlephasetogroundshortcircuitdrawsverylittlefaultcurrent.不接地系统通过隔离电容接地，因此单相接地故障会产生非常小的故障电流Toallowrapiddetectionandautomaticclearingofgroundfaults,andtoreduceinsulationandarrestercosts,groundedsystemshavebecomemorecommonthanungroundedones.为了快速检测和清除接地故障，并且降低投资在隔离设备和避雷器上

5、的费用，接地系统的应用越来越广泛。7/30/20214HUIREN@NCEPUInmanycases,thepowertransformersinagroundedsystemareconnecteddeltawye,withthewyeneutralgroundedtothesubstationgroundmat.很多情况下，接地系统中的电力变压器的连接方式为三角星型接线，星型接线的中性点和变电站的接地网相连。Generatorsandstep-downtransformersservingonlythree-phaseloadsa

6、reoftengroundedthrougharesistancetolimitthegroundfaultcurrenttolowvalues.发电机和只带三相负荷的降压变压器一般通过电阻接地，以降低接地故障电流的大小。7/30/20215HUIREN@NCEPUGeneratorstep-uptransformersandstep-downtransformersservingfour-wiredistributionsystemareusuallyconnecteddeltaontheprimaryandwyeontheseco

7、ndary.Rememberprimarymeansinputandsecondmeansoutput,soastep-uptransformerprimaryisthelow-voltagesidebutastep-downtransformerprimaryisthehigh-voltageside.发电机升压变压器和向四线配电系统供电的降压变压器通常在原边侧为三角型连接，在副边侧位星型链接。需要注意的是原边指输入，副边指输出，因此升压变压器的原边为低压侧，但降压变压器的原边为高压侧。7/30/20216HUIREN@NCEPUD

8、istributiontransformersonfour-wiresystemsareconnectedphasetoneutral(singlephase)orwye(threephase)ontheprimarys