Study of composite insulator leakage current characteristics in contamination and humidity conditions

Formation of contamination flashover arc in composite insulator is closely related to leakage current, which is affected by surface contamination and humidity. In this paper, a composite insulator in service over 6 years was taken as a sample, and leakage current tests were carried out in an artificial climate facility, which can provide experiment conditions with a series of humidity and contamination levels. Based on leakage current information collected from different flashover pattern, reasons of variation in leakage current waveforms were analyzed. The results indicate that, under high humidity conditions, the higher artificial contamination level leads to smaller leakage current phase shift between applied voltage and higher resistive current. The current waveform distortion is considered to be mainly related to harmonic components resulting from arc discharge. Hence, characteristics of leakage current waveforms can be exploited to evaluate surface discharge of the composite insulator.