高湿度环境下接触网腕臂复合绝缘子泄漏电流频谱分析

摘要

为提取接触网腕臂复合绝缘子污秽程度的有效特征,本文主要针对污秽放电过程中的泄漏电流进行频谱分析。首先根据泄漏电流的各次谐波幅值在污秽增加时增长速率不同的特点,针对污层充分受潮时采集的泄漏电流数据进行 FFT变换,提取5次谐波与3次谐波的幅值比η；其次以短时傅里叶变换(Short Time Fourier Transform,STFT)作为时频信号分析工具,计算泄漏电流时变功率谱曲线形状系数有效值λ,并分别以5次谐波与3次谐波幅值比η和时变功率谱曲线形状系数有效值λ作为污闪预警的特征参数。试验表明,上述两项频谱特征量与污秽度δ都有很好的指数拟合关系。因此在相对湿度较大(>95%)情况下,借助泄漏电流的η值和λ值,可以判断绝缘子表面受污程度,给铁路接触网维护人员开展检修工作提供一定数据参考。%In order to obtain effective contamination characteristics of composite insulator for OCS cantilever, this article analyzes the spectrum of leakage current during contamination discharge.In connection with the characteristics of different growth rates of leakage current harmonic components when pollution severity increa-ses,FFT conversion is used based on leakage current data samples when the insulator dirt layer is sufficiently damp,to obtain the amplitude ratio of 5th harmonic component to the 3rd(η).In addition,as a time-frequency signal analysis tool,Short Time Fourier Transform (STFT)was employed to calculate the RMS of shape factor of time-varying power spectral curve(λ).The ratio of amplitude value between 5th harmonic component and the 3rd(η)and the RMS of shape factor of time-varying power spectral curve(λ)are selected as the pre-warning characteristic parameters for pollution flashover.Testing results show the two spectral characteristics and the degree of contamination(δ)have a good exponential fitting relationship.Therefore,the spectral characteristics of the two leakage current values(ηandλ)are used to estimate the contamination condition of insulator surface in high humidity environment(>9 5%),providing a reference for the railway catenary maintenance personnel to carry out servicing.