Research On Relay Protection Algorithm For UHV Transmission Line

As the global energy Internet is put forward and developing,EHV transmission technology can not content the requirements of successive regional interconnection and long-distance transmission system,the development of UHV long distance transmission system become inevitable.UHV transmission system is the core part of the global energy Internet,so it is more strict for its security and stability.UHV relay protection is assuming the important mission of the entire network security and stable operation.So it is great significant to the safe and stable operation of UHV transmission lines of improving the rapidity and precision of relay protection algorithm.This paper starts from the aspects of relay protection based on power frequency and relay protection based on transient quantity,and proposes the improved time-domain capacitive current compensation algorithm and the improved segmented Prony algorithm respectively to promote the performance of relay protection for UHV transmission lines.The capacitive current makes the current differential protection performance of the UHV transmission line worse,the conventional capacitance current compensation algorithm,is on the capacitive current compensation,but there are still problems of line failure in the area affected by the point of failure in which compensation is not accurate.And time-domain capacitive current compensation algorithm based on fault location is proposed.The compensation algorithm utilizes the transient characteristics of the fault and compensates the transient capacitance current partly,and compensates the capacitor current accurately.In ensuring the reliability of the fault outside the area,at the same time greatly improving the sensitivity of the current differential protection when line failure in the area.UHV transmission line voltage level is high,and the structure is complex,fault signal contains abundant transient components.Segmented Prony algorithm has higher accuracy than traditional Prony algorithm for analyzing discontinuous faulty singals or faulty singals with mutated components.This paper analyzes the existing piecewise Prony method based on the mean square relative error(MSRE),which has the defects that the piecewise results are not entirely accurate and being affected by noise seriously,and the piecewise Prony method based on wavelet transform is proposed.The proposed algorithm is not affected by noise and has high calculation speed and can improve the speed and accuracy of extracting the transient component in fault signal.Besides,for the characteristics of the failure phase recovery voltage of the UHV transmission line with shunt reactor,the improved segmented Prony algorithm is used to analyze the fault phase recovery voltage signal of instantaneous failure and permanent failure,and distinguish effectively the fault nature of the UHV transmission line with the shunt reactor.At the same time,the characteristics of the conductor modulus dominant frequencies of the UHV transmission fault current when different fault types are analyzed,and the fault phase selection scheme based on the conductor modulus dominant frequencies is proposed.The results of the phase selection are not affected by the transition resistance and the fault distance,and the speed of protection are improved effectively.