Prediction of flashover of silicone rubber insulator under different contaminated surface conditions

The main objective of any power utility is the reliability which is sometimes affected due to failure of outdoor insulators. The insulators of transmission line passing through the coastal area are subjected to marine pollution which contains Sodium chloride (NaCl). In presence of fog or rain, this pollution known as contaminant may lead to flashover of insulator. In this paper an approach to predict the flashover is reported. Experimental set-up was prepared to energise 11 kV composite insulators under AC supply, to create artificial humidity and to measure leakage current under different conditions. Harmonics components of leakage current are analysed by using Fast Fourier Transform (FFT). It was found that when severe arc occurred on the surface of insulator, low frequency components are going to increase especially 3rd and 5th harmonics. The final analysis revealed that the development of flashover due to contamination could be predicted from the analysis of the ratio of 3rd to 5th harmonics of Leakage current signal.