Self-similar properties of minimum sparkover voltage in air for both polarities in rod-plane (0.1-30 m) gaps

It is suggested that the sparkover voltage can be described in terms of two parameters: (1) the minimum energy per unit length, W, supplied to the leader channel to enable the channel to elongate and (ii) the corresponding (average) value of the field, E, in the corona (streamer) cloud. For positive polarity W=80 J m -1 and E=5 kV cm -1 , and for negative polarity W approximately=118 J m -1 and E=16 kV cm -1 . The formulation can be extended to cover other electrode configurations and dielectrics.