High voltage research (breakdown strengths of gaseous and liquid insulators) and environmental effects of dielectric gases

Electron attachment on three perfluoroalkanes, two thioethers, n-C3F8, (CF3)2S, 1-C3F6, and 3,3,3C3F3H2 was studied. The attachment rates for CC13F were measured. The energies in dissociative electron attachment of C3F8, n-C4F10, and n-C6F14 were evaluated. Desirable characteristics and some candidate gas mixtures or gases used in diffuse discharge interrupting switches are discussed. The effect of electrode by sparking on observed breakdown voltages were studied. The observed variations of time to breakdown for various mixtures are discussed. Methods for reducing the harmful effects of small conducting particles in gas insulated apparatus were studied. The possible use of gases to form an insulating coating on offending particles, the effect of coating particles and ways to perform the coating were investigated. For sparking in SF6, SF4 was found to be a major product. The toxicity of gas mixtures before and after sparking was assessed. It is shown that effects of capacitance on the observed breakdown strengths of dielectric liquids increases capacitance lowers the breakdown voltage, however, less for external capacitance than for internal capacitance.