Effect of cold fog on leakage current characteristics of polluted insulators

Due to the wide range applications of high voltage insulators in power network systems, the reliable performance of insulators is challenged by different climate conditions including soluble and non-soluble contaminations. High voltage insulators installed near coastal areas are heavily contaminated with sea salt. In winter, due to the combined effect of sea salt and cold fog deposition, leakage current (LC) may flow on the insulators and surface degradation may take place, which may lead to surface flashover and consequently, to premature failure of power network systems. The leakage current waveform has a strong relationship with the contamination level, fog conditions and applied voltage. The investigation of LC before the flashover is essential to the reliability and secure operation of outdoor insulators. To determine the leakage current (LC) performance of high voltage silicone rubber insulators, laboratory investigation was carried out in an environmental chamber to understand this phenomenon and to simulate different behavior on the insulator surface. The performance of LC was investigated in laboratory during three different periods i.e. wetting period, drying period and dry band arcing period. Also for better understanding of insulator leakage current response an electrical model was used for computer based simulation using EMTP software. The relationship was analyzed on experimental and simulation work on the bases of magnitude and total harmonic distortion (THD).