AC Flashover Tests at Project UHV on Ice-Coated Insulators

This paper presents results of experimental studies on the flashover strength of ice-coated insulators. Two types of flashover have been found on ice-covered insulators. One is caused by hard and dry ice formed in temperatures lower than 15 °F. Another is caused by mixed conditions of ice and misty rain in relatively high temperatures of 20 to 30 °F. The flashover voltages of 25 units of 53/4- by 10-inch insulators were 288 kV (phase to ground) in the former condition and 246 kV in the latter. These results were obtained for uncontaminated insulators. Nonuniform voltage distribution along the insulator string produces these low flashover voltages. These tests were conducted at General Electric´s Project UHV in the winter season of 1968-1969.