Initiation and propagation thresholds of positive prebreakdown phenomena in hydrocarbon liquids

This paper presents an experimental study of the initiation of positive streamers under step voltage in point-plane geometry, in a number of hydrocarbon liquids. The experimental conditions (point tip radius, pulse risetime, gap length) were strictly controlled in order to take valid measurements of the initiation fields and threshold propagation voltages of streamers. Transient currents associated with the initiation of positive streamers were recorded down to the μA range with a sensitive differential measurement technique. The different current shapes obtained in the liquids studied are presented. The measured inception fields of positive streamers and propagation thresholds of filamentary streamers are discussed according to the properties of the liquids (ionization potentials and mobility of charge carriers)