A unique experimental validation in atmospheric flashover phenomena

Abstract

Lack of flashover robustness has been shown to catastrophically damage energy systems. A greater general understanding is needed to be able to design modern energy systems around this unique failure process. A flashover is a disruptive discharge through air around or over the surface of insulation produced by the application of voltage wherein the breakdown path becomes sufficiently ionized to maintain an electric arc. Flashover in insulators has in the past been shown to occur at the interface between insulator, conductor and air (or some other insulating medium) and is known as the triple point. The focus of this study is on the adverse effects of flashover on thin polyester and polypropylene films cut to initial lengths and widths of 12 /spl times/ 3/4 respectively. The thickness for the polypropylene film is 7 microns while the polyester is 4.5 microns. The bulk resistance for the polypropylene film is 7/spl Omega//square inch and for polyester is 3/spl Omega//square inch. Flashover on the samples was initiated by the application of 2400 V/sub ac/. Preliminary results have shown that the thin polyester film is resistant to flashover formation and sublimates upon the application of the test voltage. However, the polypropylene was able to sustain the flashover without sublimating. Upon further investigation, the polypropylene would sustain flashover when scaled down linearly in voltage and length to a minimum of 150 V/sub ac/ and 3/4 length. Little is known of flashover basics, and this fundamental work, for the very first time, both experimentally validates and theoretically explains the behavior for a phenomenon of grave robustness concern for energy systems.