A model has been developed for calculating the field distribution of polluted post insulators during flashover under AC voltage. The field distribution is calculated with an efficient finite-element method and verified by measurement. The effect of the field pattern on the propagation of local arc is analyzed and a modified mechanism of pollution flashover process is presented. This takes into account not only the tangential electric field component but also the contribution of the normal field component to the flashover process. The potential use of the model for analyzing the pollution performance of other high-voltage power equipment such as bushings, surge arresters, and current transformers is discussed in the light of the results obtained.
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