染污绝缘子安全区泄漏电流检测中去除信号干扰方法

Application of De-noise Methods Used in Monitoring Leakage Current in Safety Stage of Contamination Insulators

针对染污绝缘子安全区泄漏电流信号包含大量噪声干扰、很难准确提取其有效特征量的问题,利用4种小波阈值去噪方法对不同信噪比的实测安全区泄漏电流信号进行去噪,提取去噪前后的泄漏电流波形、有效值以及3次谐波与基波幅值比这3个特征量,对比分析了其去噪效果,优选出最适合安全区泄漏电流特征量提取的小波去噪方法。通过分析得出在信噪比大于1.0时,对于安全区泄漏电流波形和有效值,自适应阈值是最佳的去噪方法;对于3次谐波与基波的幅值比,4种阈值去噪法获得的比值对真实比值的逼近效果基本一样。综合比较实测信号提取的各个特征量去噪前后的效果可知,自适应阈值法是提取安全区泄漏电流特征量的最佳去噪方法。

As the leakage current in the safety stage of contamination insulators comprises a large quantity of noises, it is difficult to obtain the valid characteristics of signals. Four wavelet threshold de-noise methods are used respectively to filter the noises from measured leakage current with different signal-to-noise ratios （SNR）. Three characteristics, namely, the waveforms, effective value and amplitude value ratio of the triple-harmonic to first-harmonic of pre-and-post de-noised leakage current are acquired, whose de-noise effects are compared and analyzed. The optimal wavelet threshold de-noise method for the leakage current in the safety stage is selected. It is shown by analysis that when SNR is greater than 1.0, the best de-nolse method is the self-adaptive threshold method for the waveforms and the effective value of leakage current in the safety stage. However, the approximation effect is basally the same for another characteristic, i.e. amplitude value ratio of triple-harmonic to first-harmonic. As a general result, it is known that the self-adaptive threshold method is the best for extracting the characteristics of the leakage current in the safety stage.