小波包分析和小波包能量介绍

基于五次谐波和小波重构能量的配电网单相接地故障的选线方法研究*

孙其东，张开如，伊利峰，宋祥民，李娅芸

(山东科技大学 电气与自动化工程学院 山东 青岛 266590)

摘要: 对配电网经常发生的单相接地短路故障，因为故障点电流非常小，很难通过五次谐波幅值比较来准确地判断故障线路。提出了五次谐波和小波包能量相结合的方法。利用小波包对各线路的零序电流的五次谐波进行三层小波包分解，对第三层重构系数进行能量计算求出总的能量值。通过比较各线路零序电流五次谐波的能量值判断出故障线路。搭建了10kV中性点经消弧线圈接地的小电流单相短路接地系统的仿真模型，结果表明五次谐波与小波包能量结合的分析方法能够准确地进行故障选线。

关键词: 配电网；五次谐波；小波包；能量计算；仿真

中图分类号：TM773 文献标识码：A 文章编号：1001-1390(2016)00-0000-00 Research of single-phase?fault earth fault line selection method for the distribution network based on fifth harmonics and wavelet reconstruction

Sun Qidong, Zhang Kairu, Yi Lifeng, Song Xiangmin, Li Yayun

(College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590, Shandong, China)

Abstract: In view of frequent single-phase grounding fault in distribution network system, because the fault point current is very small, so judging fault line accurately becomes very difficult through fifth harmonics amplitude comparison. The method of fifth harmonics and the combination of wavelet packet energy are presented. The wavelet packet is used to do the third layer wavelet packet decomposition on fifth harmonics of zero sequence current of each line, and then, the total energy on the third floor reconstruction coefficient is calculated. By comparing the fifth harmonic energy of the zero sequence currents, the fault line can be judged. By setting up 10 kV neutral points via arc suppression coil grounding current of single phase short circuit grounding system simulation model, the results show that the method of fifth harmonics and combination of wavelet packet energy can accurately select the fault line.

Keywords: distribution network, fifth harmonics, wavelet packet, energy calculation, simulation

0 引 言

配电系统所出现的故障里，很大部分是单相接地故障。当小电流接地系统出现单相接地故障的时候，因为故障点此时的电流特别小，并且三相彼此间的线电压是对称的，对负荷供电一般没有影响，所以一般情况下允许系统运行一到二小时，没有必要立刻跳闸[1-4]。但是单相故障发生后，另外两相对地电压要比最初的电压高锝多，考虑到避免其发展成两点或者三点接地故障，这时就应该发出及时信号，以便相关工作人员采取相应的措施消除故障危险。

本文通过对各配电线路零序电流五次谐波提取，然后运用小