中文摘要：

绝缘子的泄漏电流和绝缘子的健康状况密切相关，可以综合反映污秽程度、受潮程度、绝缘子承受电压以及绝缘子缺陷等因素。泄漏电流中含有丰富的绝缘子运行状况的信息，它的时频熵可以描述时频平面上频谱能量分布的均匀性。根据泄漏电流不同发展阶段时频熵的分布情况，提出用EMD方法得到的时频熵作为特征量对绝缘子健康状况进行评估和预测。通过实验，得到了随着RH变化的时频熵值。根据它的变化，可以得到绝缘子的污秽情况；同时将其与同等条件下的三次谐波与基波的幅值比进行对比，显示了它的合理性。

英文摘要：

Insulator leakage current is the comprehensive reflection of the various factors related with insulator condi- tion, namely, status of contamination, degree of humidity, voltage load and insulation defect. Insulator operation in- formation is largely conveyed in the leakage current; in particular, its time-frequency entropy can describe the uni- formity of the spectral energy distribution on the time-frequency plane. According to the time-frequency entropy distri- bution of leakage current at different development stages, this paper proposes that the EMD-based time-frequency en- tropy be adopted as characteristic parameter to assess and predict the condition of insulator. Through the experiment, the time-frequency entropy is extracted changing with relative humidity （RH）. Thereby, the contamination status of the insulator can be identified; meanwhile, compared with the amplitude ratio between the third harmonic and funda- mental wave in the same condition, the time-frequency entropy is verified to be reasonable.