Study On The Main Malfunction And Counter-Measures Of Transformer Differential Protection

Along with the development of UHV power transmission system and the construction of Smart Substation in China,the research and application of UHV power grid in China have already entered the international advanced level.Differential protection as the main protection of the power transformer,the reliability of the action determines the stable operation of the power system.In the process of the development of electric power engineering,the differential protection of the transformer is replaced by the differential protection of the relay and the differential protection of the transistor.The operation reliability of microcomputer based differential protection has been improved,but in practical engineering,because the counter measures in the implementation is not achieved,project acceptance,technical test not carefully,to send electricity load test vector operation fault zone,protective current transformer used around the and measurement around the error,the differential current loop current transformer are a plurality of grounding location,when no-load closing of transformer magnetizing inrush current,lack experience in smart substation operation.In the operation SV soft pressing plate cast back not reasonable etc.factors caused by differential protection false action still occur.First of all,the thesis of the transformer differential protection scope in detail under different connection mode of study,it is concluded that the scope of protection in each side of the current transformer contains interval,to judge fault transformer differential protection action is correct;Secondly,in this paper,the principle of the transformer differential protection criterion excitation inrush current waveform symmetry principle,second harmonic brake principle and discontinuous Angle principle and differential current balance compensation methods,a detailed analysis of two kinds of ratio brake differential protection action features,and then explores its action implementation logic;Pick out the engineering application of typical ranks since PST1200 series protection device,safety measures for its calibration and validation method in detail,provide a reference for engineers in the on-site equipment maintenance advice.Finally,in accordance with engineering of secondary loop multipoint earthing interference current and main transformer differential protection caused by lateral rheological change than inconsistent polarity wiring,intelligent substation main transformer protection unilateral SV receive soft linking piece not input,current transformer,choose the wrong accurate level,excitation inrush current on the no-load switching-in transformer differential protection misoperation caused by the typical cases,detailed analysis of the cause maloperation,and combined with common protection misoperation,represented by loading vector test some in engineering precautions to prevent from transformer differential protection misoperation.