Abstract: There is a large number of noise when insulator leakage current of overhead contact system is taken. EMD（Empirical Mode Decomposition） has the problems of end effect and illusive component in actual use. In this paper, similar extrema extension method and the ratio of power method are used to solve the problems existing in EMD, and then, wavelet threshold is combined to de-noise the leakage current. Improved EMD threshold de-noising method and wavelet threshold de-noising method are used respectively to remove the noise from both the simulated leakage current and the leakage current gathered in the high voltage experiment. Estimate the results through the analysis and comparison of three characteristics of the signal pre-and-post de-noised, including effective value, the amplitude value ratio of triple-harmonic to fundamental and signal-to-noise ratio（SNR）. It is shown that similar extrema extension method and the ratio of power method can solve the problems of end effect and illusive component, the de-noising result of de-noising method based on improved EMD threshold method is better than wavelet threshold method. At the same time, improved EMD threshold method is self-adaptive, therefore, is suitable to dirty wet insulator leakage current of overhead contact system de-noising.

Key words: overhead contact system insulator, leakage current, improved Empirical Mode Decomposition（EMD）, signal de-noising

摘要： 采集接触网绝缘子泄漏电流时存在大量干扰，且使用经验模态分解（Empirical Mode Decomposition，EMD）方法去噪时存在端点效应和虚假分量的问题。提出利用类似极值延拓法和功率比值法（The Ratio of Power，TRP）解决EMD存在的上述问题，结合小波阈值方法对泄漏电流进行去噪。选择小波阈值去噪作为对比，对泄漏电流仿真模型和高压实验采集的泄漏电流进行去噪处理。通过去噪前后的有效值、三次谐波和基波幅值之比和信噪比对去噪效果进行评价。结果表明类似极值延拓法和TRP法可有效解决端点效应和虚假分量问题，改进EMD阈值去噪方法去噪效果优于小波阈值去噪。改进EMD阈值去噪方法具有自适应性，适用于污湿情况下的绝缘子泄漏电流去噪处理。

关键词: 接触网绝缘子, 泄漏电流, 改进经验模态分解阈值, 信号去噪