Studies of impulse creepage discharge in transformer oil

The propagation of a creepage discharge on the surface of a solid insulator in transformer oil is investigated in the case when an impulse voltage with various values of duration is applied to a point-to-back electrode. The propagation process was observed in detail by using an ultra-high-speed photographic method combined with a schlieren optical system and a dust figure method. The discharge current and the amount of charge stored on the solid insulator were measured simultaneously. The shape and size of the schlieren figure agree well with those of the dust figure. The propagation of density changes caused by a streamer discharge corresponds to the current and charge waveform