The Effect of Lightning on Insulator Flashover Characteristics

Lightning transient has detrimental effect on electrical system. This paper discusses the effect of lightning on insulator flashover characteristics in railway traction mast. The dependence of footing resistance and soil ionization on flashover behavior is explored. The CI GRE model of lightning stroke is considered for analysis. The modeling and simulation is carried out using Electro-Magnetic Transient Program (EMTP) software. It is observed that footing resistance strongly affects the insulator flashover characteristics. With increase in footing resistance, insulator is most likely to flashover. Leader development model is used to understand leader propagation along insulator surface causing flashover. The non-linear behaviour of footing resistance due to soil ionisation is seen to increase the flashover time and occurs at the tail end of lightning stroke. Further, the effect of double exponential lightning stroke model is studied. It is observed that flashover occurs early with CIGRE model compared to double exponential model.