High Speed Electrical Breakdown Mechanisms in Gaseous, Liquid and Solid Dielectric Materials

Abstract

Far-reaching similarities between the mechanism of electrical breakdown in the three insulating media - gaseous, liquid and solid - have been found , In all media, discharge channels of a similar type, generally referred to as streamers, are formed which differ for each electrode configuration. In a divergent field of a point-plane electrode system, streamers are generated in the vicinity of the point-electrode, They are subsequently promoted by direct ionization and photoelectric ionization processes in the direction of the plane electrode. The charge carriers remaining behind in the streamer tail, due to their ionized state and space charge, affect the subsequent processes. A model for streamer propagation in gaseous dielectrics i s presented and its relationship to the characteristics of discharge growth is discussed. The initiation phase is considered first , leading to primary, secondary and return streamers, and finally to possible transition to arc - over. It is suggested that the same pattern of events applies to electrical breakdown of liquids and solids based on the many points of similarity observed in the growth of discharge in the three media.