Time-to-Flashover Characteristics of Polluted Insulation

It is shown that times to flashover obtained by von Cron and Dorsh with alternating voltage on an artificially polluted insulator can be fitted into a relation ( V
²
-V
₀
²
) t = KR2 where V is the applied voltage, t is the time to flashover, R is the resistance of pollution, and Vo and K are experimental constants. Experiments were carried out using pulse unidirectional voltage applied to a narrow conductive path of water solution of sodium chloride, and the empirical expression obtained was V
²
-V
₀
²
) ≈ CR
²
L
³
where L is the leakage length and C is another experimental constant. These relations are explained as results of an energy equation p·δt = e·δt whereδt at is the time required to extend the discharge by δx, p being the power available for the discharge Propagation and e the energy required to elongate the discharge by a unit length.