Flashover Performance of Artificially Contaminated and ICED Long-Rod Transmission Line Insulators

The 60 Hz flashover performance of 230 kV and 500 kV long-rod polymer insulators is compared to standard ceramic suspension insulator strings under moderate ice conditions. The tests on clean and heavily pre-contaminated insulators were performed indoors to minimize the effects of wind and temperature variations. In general, contaminated and iced long-rod insulators with disc-shaped sheds of uniform diameter do not perform as well as insulators having conical- shaped sheds of alternating diameters. All 230 kV long-rod insulators tested show an improved performance over conventional ceramic insulation of equivalent length. At 500 kV, only those long-rod polymer insulators that have conical-shaped sheds of alternating diameters show an improved performance over conventional ceramic insulation. A mechanism describing the flashover of contaminated and iced insulators is proposed and discussed in relation to long-rod insulator designs and performance.