本科毕设论文-—变压器差动保护的研究.doc

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1、陕西理工学院毕业论文毕业论文变压器差动保护的研究[摘要]电力变压器作为联系不同电压等级网络的设备，是电力系统中非常重要的元件。长期以来电力变压器一直只采用差动保护作为内部故障的主保护。因此，差动保护的可靠性和安全性对变压器保护来说最为关键。其中励磁涌流的识别一直是研究的热点，国内外许多研究人员做了大量工作，也取得了许多成果。由于变压器励磁涌流受变压器铁心剩磁、饱和磁密、系统阻抗、接线方式、铁心结构、合闸初相角等因素影响，所以这些方法都不能保证百分之百的可靠性，鉴别励磁涌流的问题成为制约变压器差动保护能否正确和灵敏动作的瓶颈

2、。本文研究了变压器产生励磁涌流的机理，分析了几种鉴别励磁涌流方法的优缺点。针对二次谐波制动原理存在着不着之处，提出了基于等效瞬时电感鉴别励磁涌流的方法并用MATLAB/SIMULINK建立了仿真模型，对变压器在不同合闸角、不同剩磁的情况下进行了大量仿真。仿真结果表明基于等效瞬时电感鉴别励磁涌流的方法能够有效鉴别变压器的内部故障和励磁涌流，具有一定的实用价值。[关键词]变压器差动保护MATLAB/SIMULINK励磁涌流等效瞬时电感仿真Expioitationtransformerdifferentialprotection

3、第1页共49页陕西理工学院毕业论文LiXin(Grade06Class3,MajorElectricengineering，ElectricengineeringandautomationDept.，ShaanxiUniversityofTechnology，Hanzhong723003，Shaanxi)Tutor：YangLinxiaAbstract：Powertransformersasveryimportantelementsinpowersystemrequireveryreliableprotectionhasb

4、eenadoptedasmainprotectionagainstinnerfaultoftransformerforalongtime,sinceithashighreliabilityandhighsensitivity,whicharemostimportantfortransformerprotection.Identificationofinrushcurrenthasbeenakeyproblemtoberesolved.Manyresearchereshavedonealotofworkonthisaspec

5、t.Becausetheinrushcurrentoftransformerisinfluencedbymanyfactorssuchasresidualfluxofironcore,saturationfluxdensity,systemimpedance,modeofconnection,ironcorestructure,closingangleandsoon,butalloftheproposedmethodscan’tmakesure100%reliability,Identificationofinrushcu

6、rrentisthemostcriticalfactorthatlimitsdifferentialprotectionoperation.Inthisthesis,themechanismofinrushcurrentoccurringintransformeriswellresearched,theadvantagesanddisadvantagesofseveralmethodsforcheckinginrushcurrentarediscussed.Basedonequivalentinstantaneousind

7、uctancetodiscriminatebetweeninternalfaultcurrentandinrushcurrentisputforwardinthisthesis.AnumericsimulationmodelisbuiltwiththesimulationsoftwareSIMULIINKbasedonMATLAB,numeroussimulationsarecarriedoutonanconnectedtransformerwithdifferentswitching-onangleandremanent

8、flux.Thesimulationresultsshowthattheproposedmethodbasedonequivalentinstantaneousinductancepossessescertainpracticabilityandcandistinguishinternalfaultcu