INITIATION AND PROPAGATION THRESHOLDS OF POSITIVE PREBREAKDOWN PHENOMENA IN HYDROCARBON LIQUIDS

This paper presents an experimental study of the initiation of positiv e streamers under step voltage in point-plane geometry, in a number of hydrocarbon liquids. The experimental conditions (point tip radius, p ulse risetime, gap length) were strictly controlled in order to take v alid measurements of the initiation fields and threshold propagation v oltages of streamers. Transient currents associated with the initiatio n of positive streamers were recorded down to the muA range with a sen sitive differential measurement technique. The different current shape s obtained in the liquids studied are presented. The measured inceptio n fields of positive streamers and propagation thresholds of filamenta ry streamers are discussed according to the properties of the liquids (ionization potentials and mobility of charge carriers).