Cavity initiation through an evaporating mechanism for the pulse breakdown in liquid

This paper presents an analytical model which describes the dielectric strength of insulating liquids stressed with the impulse electric fields. The Joule heating by the space charge saturated current may cause over-heating of pure liquids or may result in generation of nucleation centers associated with impurities in the case of practical liquids. Evaporation of the liquid from these impurities has been analysed in the paper and formation criterion for percolation chains of gas bubbles in impure dielectric liquids has been established. Based on this percolation condition, the dielectric behavior of n-hexane has been studied. Breakdown volt-time characteristics of liquid n-hexane have been calculated for different temperatures, and its dielectric strength has been obtained as a function of externally applied pressure.