交流方波下局部放电信号检测技术-Read.doc

摘 要 在高频、高压下工作的电力设备常常会出现局部放电现象，局部放电是导致绝缘破坏的原因。研究局部放电的检测，有助于了解局部放电的破坏机理，对电力设备绝缘的设计有重要意义。本文主要研究在交流方波下基于脉冲电流法，利用宽频带的示波器和高性能的计算机作为平台，构建一个局部放电的检测系统。 交流方波下，局部放电脉冲集中在方波的上升沿，由于方波含有丰富的高次谐波，这给局部放电检测带来了困难。本文的局部放电检测系统提供了一种对从示波器采样得到的放电波形进行数字滤波处理的方法。利用小波分析工具设计了一个针对交流方波下的局部放电信号的滤波方法——小波阈值门滤波法，利用该方法对模拟的放电信号处理过程进行仿真分析，讨论了不同方波的幅值、上升沿和信噪比对提取局部放电信号的影响。 关键词：局部放电，局放检测，信号处理，小波阈值门，示波器 ABSTRACT Working in high frequency and high voltage conditions, partial discharge (PD), which causes the failure of insulation, always breaks out in the electrical equipment. Studying the PD detecting will benefit for understanding the failure mechanism and be significance for the designs of the insulation of electrical equipment. This paper mainly research the method for constructing a system for PD detecting, basing on impulse current way with the platform of wide frequent band oscillograph and high-powered computer, on square wave condition. The PD impulse mostly appears during the rise time of the square wave. For the square wave contains rich high frequency, it is difficult for the PD detecting. The PD detecting system in this paper provides a measure of digital process for picking out the PD signal from the wave that sampled by the oscillograph. A new method, called wavelet gate, is introduced, which is designed with the wavelet analysis tools and is for the PD detecting on square wave condition. With this method, the paper discusses the infections on picking out the PD signal with different amplitudes, rise times and signal noise ratio of the square wave conditions by simulant wave in the simulate analysis mode. KEY WORDS: partial discharge，PD Detecting，signal process，wavelet gate，oscillograph 目录 第1章 绪论………………………………………………………………………… 1.1 局部放电检测的背景和意义…………………………………………… 1.1.1 局部放电的定义及产生原因…………………………………………… 1.1.2 局部放电检测的研究现状与发展…………………………………… 1.2 局部放电的检测方法……………………………………………………… 1.2.1 局部放电检测方法的分类…………………………………………… 1.2.2 各种局部放电检测方法及优缺点…………………………………… 1.3 本文的主要工作…………………………………………………………… 第2章 交流方波下局部放电检测原理………………………………………