Leakage Current and Flashover Performance of Iced Insulators

Abstract
White arc and flashover of long rod and porcelain insulators under glaze and rime icing are studied. During icing periods ice is accumulated on the insulator under H. V. applied at a constant temperature until a flashover occurs or a thickness of ice measured on a monitoring conductor reaches 7 cm. During deicing periods, the ambient temperature is allowed to increase at different rates over the freezing range. Results show that, for each kind of insulator, there is a flashover threshold current, which is 120 mA for the long rod insulator tested, and 180 mA for the porcelain insulator. Thickness of ice accretion at which flashover occurs (flashover threshold thickness) is smaller, during icing period than during deicing periods. Hard rime, of 0.87 in density is the most dangerous kind of ice: white arc and flashover occurs at very low thickness of this ice. Flashover threshold thickness of ice depends on the rate of increase of the temperature during deicing periods. The effect of the wind direction on insulators flashover performance is also investigated.

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