Influence of non uniformity of pollution thickness on insulator flashover under impulse voltage

This paper is aimed at the influence of the linear non uniformity of pollution layer on critical flashover voltage V_cri of polluted insulator under lightning impulse voltage. It is shown that the experimental values of V_cri depends on the configuration of pollution and the polarity of voltage. A mathematical model enabling to compute the flashover discharge characteristic constants (n and N) and the critical thickness of pollution layer and thence the critical flashover voltage is presented. It´s also shown that n and N are not static and they depend on the parameters of the equivalent electrical circuit, thermal characteristics of discharge and the condition of propagation. The computed critical voltages are found in a good accordance with the experimental ones.