A study of short-time ac flashover voltage of contaminated insulators and a consideration of its application to transmission line insulation design

Insulator contamination is the decisive factor in making insulation design of most transmission lines in Japan. This paper describes the performance of contaminated insulators against a short-time ac overvoltage in the order of several cycles, taking into consideration comparatively higher overvoltage due to the one-phase-to-ground fault of recent long-distance bulk power transmission lines with series capacitors. It has been made clear by this study that, in the case of a fault clearance within 0.07 sec, e.g., the flashover voltage increases by about 15% more than in a continuous energization. This implies that the insulation of series-capacitor-compensated lines can be met by the conventional insulation design levels.