Polarity effect of DC contamination flashover of composite insulators

The negative contamination flashover voltages of porcelain insulators are lower than the positive ones, and this phenomenon is called polarity effect. Silicone rubber composite insulators have been extensively accepted in the region of external insulation, but up to now, it is not clear yet whether their DC contamination flashovers have polarity effect. In this paper, the polarity effect of DC contamination flashovers of the porcelain insulator is analyzed, and it is thought that those metal hardwares on the porcelain insulator string cause the polarity effect. Each composite insulator only has two hardwares and many short arcs can form in series on it before the flashover, so these arcs are non polarity ones and cause the non polarity effect of the composite insulator.