Rainfall resistivity and 60-cycle insulator flashover

DISCUSSIONS between American and European standards groups are currently directed toward adoption of uniform parameters for wet flashover and wet withstand tests. American published values are based on tests conducted with a spray water resistivity of 7,000 ohms per inch cube and a rate of precipitation of 0.2 inch per minute. The corresponding European test values are 10,000 ohms per centimeter cube (3,930 ohms per inch cube) and 3 mm per minute (0.118 inches per minute). Two recent papers have reported laboratory investigations relating the comparative influences of these factors.^{1, 2}