Effect of wetting conditions on the flashover voltage of non-ceramic insulating materials

Two families of nonceramic materials widely used for outdoor HV (high-voltage) insulation, namely, high-temperature vulcanizing (HTV) silicone rubber and ethylene propylene rubber (EPR), were evaluated. For silicone rubber, there is a significant reduction in the flashover voltage at higher steam input rates, whereas for EPR the relationship is similar to that established for porcelain. Under all the conditions evaluated the silicone rubber samples had a higher flashover voltage than EPR or porcelain. There are variations in the degree of hydrophobicity of silicone rubber depending on the method of fog generation and steam input rate. A method for evaluating the flashover voltage of nonceramic materials has been developed. This procedure yields comparable results to the established `up and down´ and rapid flashover techniques for porcelain and glass, and is believed to provide meaningful results on nonceramics, as there is very little conditioning of the surface during the measurement