An experimental study of flashover performance of various post insulators under icing conditions

This paper reports on the results of a laboratory study on the electrical performance of several 735 kV post insulators covered with wet-grown ice formed artificially from supercooled water droplets. The tests were performed in a cold room at the University of Quebec in Chicoutimi (UQAC) on portions of ~0.6 m of insulators, using an “icing regime” procedure and a “melting regime” procedure. The electrical performance was biased on the evaluation of the maximum withstand voltage, V_ws, as described in the standard IEC 507, which is basically employed for flashover tests on polluted insulators. The results showed that the presence of ice on post insulators considerably depresses the V_ws of the portion tested. The comparison of the results obtained for each specimen indicated that the electrical performance was related to the insulator profile and to the surface covering material. Finally, the results showed that melting conditions further decrease the maximum withstand voltage, unless some ice shedding occurs during the melting period