Study On Differential Protection And Application For Fuzhou 1000kV UHV Transformer

With the rapid development of economy in our country,the demand of all areas is increasing day by day.Power as a basic energy has a greater demand,so it is necessary to speed up the development of UHV transmission technology.and strengthen inter-regional long-distance transmission and power grid interconnection.UHV transformer is a key equipment for UHV transmission system,Main protection plays a important role for security and stability of entire power system,particularly UHV system.Compared with the 500kV transmission line,UHV transmission system has the characteristics of large capacity,long distance and low loss transmission line,,and the wire diameter is relatively large,the impedance is small,with a large transmission power,which will The relay protection system caused a greater impact.It is significant to study the UHV protection configuration,inrush current and fault current recognition.The structure of UHV transformer is quite different from the traditional transformer.The difference between 1000kV transformer and 500kV ordinary transformer is analyzed;According to the special structure of UHV transformer,the overall configuration scheme is summarized.It is concluded that voltage regulating transformer and compensation transformer independently differential protection must be configurable separately.Inrush characteristic for UHV transformer is analyzed in this paper.The deficiencies of Second harmonic restraining,Discontinuous angles and Wareform symmetary are analyzed.Two methods for solving inrush recognition are provided in this paper.For the deficiencies of second harmonic restraining,non-periodic component is proposed as its secondary criterion.Closing control strategy is presented to eliminate inrush current when energizing no-load UHV transformer.According to the structure and the operating characteristics of the UHV transformer,the protection setting calculation is provided in the last chapter of the paper.