Dielectric breakdown of sulfur hexafluoride in nonuniform fields

THIS PAPER PRESENTS some of the anomalies in the dielectric breakdown of sulfur hexafluoride SF6 as functions of pressure and electrode separation in a nonuniform field. The nonuniform field, although difficult to analyze, is of considerable importance from the engineering viewpoint as it is the condition most generally encountered in electrical apparatus. At atmospheric pressure, sulfur hexafluoride has unexpectedly high 60-cycle breakdown voltage for large gaps. In this case, the presence of corona precedes sparkover. This was termed ¿corona-stabilized breakdown¿ in a recent paper by Camilli, Gordon, and Plump.1 This phenomenon will be explained by showing the effect of electrode spacing on the position of the maximum which occurs in the curve of sparkover voltage versus gas pressure. The d-c 60-cycle and impulse-breakdown voltage, as well as corona-onset voltage, will be discussed. The time required for corona stabilization to occur will be indicated.