The propasation mechanism of impulse creepage discharges over oil-immersed surfaces

A fundamental study of the mechanism of propagation of impulse creepage streamers over an insulating surface is reported. The studies were made using high-speed cameras, still cameras, and special probes, to give a new picture of the creepage process. High-speed photographs show that impulse creepage in the nonuniform field is a stepped discharge process, remarkably similar to natural lightning except on a greatly reduced scale. Probe measurements display the variation of channel voltages with time and distance. The mechanism is discussed in considerable detail for both positive and negative polarities.