Linear Stochastic Analysis of Polluted Insulator Leakage Current

The measurement and analysis of leakage current (LC) for condition-based monitoring of, and as a means of predicting flashover of, polluted insulators has attracted a lot of research in recent years. Results presented in the technical literature show that surface arcing of contaminated insulators causes significant variations in both the magnitude and shape of the insulator´s leakage current, and several techniques have been proposed for analysis. This paper submits the results of applying linear stochastic and statistical (probabilistic) analysis as a signature analysis tool for flashover prediction. A new twist is presented based on statistical analysis of the leakage current envelope (rather than just instantaneous peak values), in particular, level crossings, mean exceedances over high thresholds, and extreme value analysis of the envelope. The analysis was performed offline using digitized samples of leakage current obtained from a data acquisition system, which continuously scans the leakage current during flashover tests in a laboratory fog chamber.