【作者】 徐荆州；

【导师】 卢毅；

【作者基本信息】 东南大学 ， 电力系统及其自动化， 2004， 硕士

【摘要】 随着社会的发展,对电能质量的要求也越来越高。GIS以其体积小,可靠性高等优点越来越多的应用于电力系统当中。GIS本质上来说是设计成不需维护的设备,然而,一旦GIS发生故障,其修复时间将更长,对电力系统的危害也更大目前,对GIS的投运前的检修工作已经作的十分完善,但是对于GIS在运行过程中的绝缘情况的监测方面却作的不够,因此不能够实时了解其内部的绝缘情况,进而不能及时排除隐患,阻止事故的发生。众所周知,GIS中绝缘的老化的一个重要因素是因为局部放电。所以,检测GIS内部局部放电的特征现象,发展一套新的诊断方法十分重要。目前已在现场使用的方法有检测放电产生的光,超声波,电流,电磁波等等,由于方法本身的缺陷或者检测后的处理问题加上现场强烈的干扰,使得检测的精度不能达到很高。针对这种情况,本文采用非接触方法,利用双锥天线检测从GIS内部泄漏出来的电磁波信号并进行处理以判断其内部是否有放电发生。针对小信号检测中出现的问题,文中提出两种方法对信号进行处理。一是局部放电信号背景直接滤除法。该方法通过对背景信号进行分析,找出其中较大的干扰频率分量并将其直接从放电信号中滤除。该方法原理简单,且比较通用,即使在强干扰的环境下,通过选用适当的阈值也能取得很好的滤波效果。二是利用小波变换方法直接提取信号。与传统方法相比,小波分析是一种时-频分析方法,具有多分辨特性。这种特性对非平稳信号反应敏感,易检测出奇异信号。从处理结果可看出,当已知放电中心频率时,滤波的效果十分理想。文章结构安排成三段式,首先介绍局放原理危害以及目前的检测方法,并粗略分析了其不足,接着介绍我所做的实验,得到实验分析数据,最后对信号进行处理,并对结果进行分析,得出最终结论。实验证明,本文所提出的方法具有一定的先进性,处理效果十分理想,达到了预期的要求。更多还原

【Abstract】 Higher and higher quality electrical power supply is needed with the development of the society. So gas insulated switchgear(GIS) has more and more applications in the power system due to its characteristics advantage, such as small volume, high quality, etc. Essentially, GIS is designed not to need maintenance. However in case of an insulation breakdown, it takes a longer time for its restoration and the breakdown causes more serious damage to system operation.Currently, many methods which are effective enough can be available for examining the GIS before running, but its insulation condition monitoring hasn’t been well done during operation, so we can’t know the insulation condition in time, and therefore we can’t eliminate the potential danger and prevent a breakdown. As is known to all, partial discharge(PD) is a symptom of an insulation breakdown occurring in GIS. So it’s very important to develop a new diagnostic technique to detect a characteristic symptom when PD occurring. At present, signals of light, supersonic wave, current and electromagnetic wave which are emitted from GIS can be utilized to determine whether PD occurs, however, the results are not satisfying due to the processing methods and the strong noise at the sites. To solve this problem, this paper proposes a noncontact detection method by using antennas to receive signals of electromagnetic wave emitted and background noise, then we filter the high-frequency parts from the original signal against the background noise, and then we use the wavelet transform to analyze the results to determine whether PD occurs.This paper has three parts, the first part introduces basic knowledge such as PD’s principle and detection methods used now whose shortcoming are also provided in brief, the second part introduces our experiment and provide the data for processing, the last part analyzes the data and discusses the results and get the conclusion.The results show that the method provided in this paper has its advance over other methods, the results are very ideal and achieve the level anticipated.更多还原