Research On Single-terminal Traveling Wave Fault Location Of Transmission Line Based On Wavelet Packet And Correlation Algorithm

At present,the principle of single-ended traveling wave fault location is still unable to accurately distinguish whether the second reverse traveling wave head is fault point reflection wave or bus-to-bus reflection wave,which leads to the low reliability of single-ended fault location.The traveling wave correlation method is one of the classical traveling wave single-ended fault location algorithms,which is widely used in the current single-ended fault location system.However,the uncertainty of time window and the unreliable extremum criterion of correlation function of traveling wave correlation method lead to the decrease of the reliability of single-ended ranging.Aiming at the problems of traveling wave correlation method,this paper combines wavelet packet and envelope to realize single-ended fault location by traveling wave correlation method.The main research contents are as follows:1.Summarizing the steps of the original fault traveling wave signal pretreatment,analyzing the basic theory of wavelet packet multi-scale transformation and the principle of single-ended traveling wave ranging based on traveling wave correlation method,two problems affecting the practical application of traveling wave correlation method are concluded: the extremum criterion of correlation function is unreliable,and the time window width of correlation algorithm is not fixed.2.In view of the unreliable extremum criterion of correlation function in traveling wave correlation method,this paper uses wavelet packet multiscale transform to filter the original fault signal and extract the characteristics of fault traveling wave signal effectively.In view of the problem of time window width of traveling wave correlation method is not fixed,two solutions are proposed: the first one is multi-scale decomposition and reconstruction of wavelet packet by db1 wavelet basis.At present,the traveling wave correlation method with fixed time windows at various scales is used.The second method uses the optimal wavelet basis to carry out multi-scale analysis of wavelet packet,and achieves multi-time window traveling wave correlation method with time windows varying with scale.3.By using the traveling wave correlation method with fixed time window width,the first step is to decompose and reconstruct the multi-scale wavelet packet on the basis of db1 wavelet base.The width of the initial head of the forward and reverse traveling wave is the same at different scales,and the width of the initial head of the forward and reverse traveling wave is used as the time window width of the traveling wave correlation method.Then,the envelope is used to extract the forward and reverse traveling wave,so that the first two can be Finally,the single-ended traveling wave ranging is realized by the traveling wave correlation method with fixed time window width.4.Because the initial wavefront widths of the reconstructed signals are different at different scales(except the base of db1 wavelet basis),the traveling wave correlation method with multi-time window widths is proposed on the basis of method one.Firstly,the optimal wavelet basis is selected by the maximum correlation coefficient,so that the multi-scale transform of wavelet packet is the best filter.Then,the multi-scale analysis of wavelet packet based on the optimal wavelet basis is carried out,and the width of the reconstructed initial wavefront of forward and backward traveling wave becomes wider with the increase of scale.At this time,the traveling wave correlation method becomes a multi-time window correlation algorithm.Finally,the envelope-processed unipolar forward and backward traveling wave correlation method with multi-time window width is used to realize single-ended ranging.5.This paper establishes a simulation model in software PSCAD,and validates the simulation data through MATLAB.The two methods are simulated and analyzed within and outside the midpoint respectively,and the influence of transition resistance and fault initial angle on the location results is verified.The simulation results show that the two methods proposed in this paper can be used to locate faults reliably at any fault point,and can be applied at different transition resistances and initial angles of faults,which improves the reliability of single-ended fault location,and provides a new development idea for modern traveling wave location technology.