Current pulse measurement corresponding to the streamer inception in dielectric liquids

In this paper, the relation between the prebreakdown current pulses and the initiation of the density change streamer in cyclohexane under impulse voltage condition was investigated. The reference electrode method and the ultra wide bandwidth method were constructed to measure the prebreakdown current pulse under impulse voltage, and a high-speed high magnification shadowgraph system was used for the streamer observation. From a simultaneous measurements of current pulse and streamer observation, it is possible to detect the first current pulse corresponding to the first appearance of the streamer inception. The first current pulse appearance occurs prior to the streamer inception for both polarities. The time difference between the onset of the first current and the streamer inception was obtained to be approximately 80 ns for a negative, and 40 ns for a positive point, respectively. For a negative point, the small spherical streamer whose volume of 0.5/spl times/10/sup -15/ m/sup 3/ corresponding to a single current pulse of 0.12/spl sim/0.45 pC was observed.