High field conduction and prebreakdown phenomena in dielectric liquids

The present paper is mainly devoted to phenomena occurring in point-plane electrode geometry, where breakdown is the result of initiation and propagation of prebreakdown phenomena called "streamers". Indeed, in this configuration, investigations of streamer initiation processes, which requires a very high electric strength (∼ MV/cm), and of propagation ones (requiring low electric field, ∼ kV/cm) can easily be made for negative streamer development as for positive one. From an analysis of experimental results in pure liquids the physical processes connected with streamer initiation and propagation are presented and discussed. Some estimations of the main parameters of a fast filamentary streamer (field strength acting on the streamer tip, field inside the channel, charge density, etc.) are obtained from qualitative considerations and compared to experimental determinations.