Research on transition condition between streamer and leader in 1 m plane-rod gap under switching impulse voltage

In this paper, the experimental results of the quantitative transition condition between streamer and leader are presented for a plane-rod gap. The charge injected into the rod, energy input caused by charge moving in streamer channel before the first leader, and charge injection during leader discharge are measured and calculated. The test gives new results: (1) the charge injected to the rod prior to inception leader point is increased correspondingly from 3.9 μC to 11.1 μC with the change of the time to peak of switching impulse from 100 μs to 250 μs; (2) the more charge needed at transition point from streamer to leader discharge, the higher the sparkover voltage, but the smaller the charge injected to the rod during the leader discharge; (3) the relationship of energy input to streamer channel and sparkover voltage is obtained. The more the energy input, the lower the sparkover voltage; and (4) in the U50% breakdown case, with increase time to peak of impulse voltage, the injected charge in the leader up to the point where voltage collapsed tends to decrease, but the instantaneous voltage at this transition point tends to increase