Flashover of Contaminated Insulators with Cylindrical Symmetry under DC Conditions

A series of experiments was done to determine how contamination flashover occurs under dc conditions. It was found that polarity influenced the flashover voltage, with flashover occurring more readily for negative polarity. Several reasons are advanced to explain this, including cathode spot phenomena, and electrochemical effects. Further experiments showed electrochemical alteration of the amount, type, and distribution of surface contaminant during simulated fog exposure. This will affect the interpretation of artificial test results and should be taken into account in evaluating insulator designs.