树型配电网单相接地故障行波测距的组合方法

Combined Method for Traveling Wave Location of Single Phase Grounding Fault in Tree Type Distribution Network

针对单端定位或双端定位方法都很难准确定位树型配电网单相接地故障的问题,文中提出一种适用于定位树型配电网单相接地故障的行波测距组合方法。利用双端法确定故障点在主干线路上的映射位置,由此判断故障位于主干线路还是分支线路。对于主干线路故障,映射位置即可确定为故障点;当故障位于分支线路时,结合映射位置蕴含的故障距离信息,在模量法测距公式基础上构建零模波速提取算法,但由于小波变换的不同尺度下零模行波的衰减和相移变化明显,导致提取的零模波速误差各不相同,为了提高分支线路的测距精度,分析了提取零模波速与母线端检测零模波速的关系,提出从多个尺度下选取精度最高测距结果的方法。利用PSCAD/EMTDC搭建仿真模型,对不同的故障情况进行仿真,结果证实该方法有效,测距精度高。

The fault point is found difficultly by using the fault location based on the one-terminal method or two- terminal traveling wave method when the single phase-to-ground fault occurs in tree type distribution network. Two-terminal method is used to determine the mapping of the fauh point in the trunk line, then that the fault is located in the trunk line or in the branch line is judged. For the fault occurs in trunk line,the fault point is located in the mapping position;when the fault occurs in branch line, combined with the fault distance information of mapping position, the zero-mode wave velocity extraction algorithm is proposed based on location method of the gap between zero-mode and aerial-mode traveling wave propagation time. However,the amplitude attenuation and the phase variation of zero-mode traveling wave are obvious in different scales of the wavelet decomposition, which will result in the error of extracted zero-mode wave velocity is different.In order to improve location accuracy of branch lines,the paper analyzes the relationship between extracted zero-mode wave velocity and zero-mode wave velocity detected in busbar,based on that the method used to select the most precision location results is proposed.Using simulation model built by PSCAD/EMTDC to simulate different fault conditions,the simulation results indicate that the method is effective and has high accuracy.