中文摘要：

为了去除污秽绝缘子安全区泄漏电流中的噪声,提出了采用小波变换去噪时分解层数的定量计算方法。根据小波去噪时需对细节进行阈值处理、安全区泄漏电流的能量主要集中在低频周期成分上的结论,提出了确定小波变换去除安全区泄漏电流噪声时最佳分解层数的判据;并以此判据为基础,提出并证明了计算小波分解层数的公式。对在高压试验中和现场采集到的绝缘子泄漏电流进行了小波去噪研究,结果表明：在相同母小波和阈值前提下,采用所提公式获得的分解层数去噪时的效果优于采用其他分解层数时的效果。从而得出结论：所提公式计算出的值为最佳分解层数,按此值去噪时效果最好。

英文摘要：

In order to de-noise the leakage current at the safety stage of the contamination insulators,we proposed a quantitative calculation method of the number of the decomposition levels when wavelet transform was used to denoise the leakage current.Based on the conclusions that details of a signal needed a threshold process while wavelet transform was used to de-noise the signal,and that the energy of the leakage current at the safety stage concentrated upon the low-frequency periodic components,a rule was proposed for judging the optimal number of the decomposition levels when wavelet transform was used to de-noise the leakage current.Thereby,a calculation formula of the optimal number of the wavelet decomposition levels was proposed and proved.The insulator leakage currents gathered in the high voltage experiment and in the field were de-noised with wavelet transform.The results show that,after selecting the same mother wavelet and the same threshold,the de-noising results with numbers of the decomposition levels from the formula proposed in this paper are superior to those with the other numbers of the decomposition levels.The conclusion can be drawn that,the value calculated by the proposed formula is the optimal number of the decomposition levels,moreover,after using this value,the de-noising is the most effective.