Impulse Flashover of Insulators

For the most part this paper is a discussion of the mechanism of insulator flashover. The breakdown of air between electrodes, with particular consideration of the effect of various factors upon the flashover characteristics of insulator strings equipped with arcing rings, is discussed. It is shown that critical dimensions and spacings of arcing rings exist for a given insulator string. If the arcing rings are designed to lie on the safe side of this critical point, cascading flashovers will not occur. If the arcing ring dimensions are below the critical values, cascading may or may not occur depending upon the nature of the applied voltage wave. Data from tests, which determined the limiting physical dimensions of arcing rings that will prevent cascading under all types of impressed voltages, are presented.