In this thesis the basic processes involved in the flashover of polluted insulators are studied quantitatively Previous theories based on instantaneous arc current - arc voltage relations are shown to be unsupported by laboratory experiments. The effect of the sinusoidally varying voltage, particularly the influence of the voltage zeros, on the propagation of arcs on a polluted surface is examined, and a flashover theory is developed, based on experimentally determined power-frequency arc relations. This theory, which is supported by laboratory experiments, enables the flashover voltages of polluted insulators to be determined as a function of the insulator parameters and the pollution conductivity.
The effect of separating the arcs on an insulator prior to flashover into a number of individual lengths is investigated, and a new type of insulator, which appears to have good pollution performance, is examined.
The requirements for good pollution performance of insulators are presented, and test methods for experimentally determining insulator pollution performance are discussed.