Positive streamer propagation in natural ester and mineral oil under lightning impulse voltage

This article describes the comparative experimental studies on streamer propagation in natural ester and mineral oil under high voltage positive lightning impulse voltage. These studies were concentrated around the small electrode gaps (5 and 20 mm) and the point-plane electrode arrangement. The spatial shapes of the developing streamers, light emission and propagation velocity were analyzed and compared between the two dielectric liquids: natural ester and mineral oil. In both of them two streamer propagation modes were registered during the studies performed. Propagation of slow 2nd mode streamers took place below the so-called acceleration voltage while fast 3rd mode streamers developed at acceleration voltage and above. Comparing the streamer shapes corresponding to a given voltage…