A Model for the Flashover Process on Non-Uniformly Polluted Insulators

Abstract

The flashover process over polluted insulators is described by well-known analytical equations, published by various investigators, mainly Obenhaus and Alston. These procedures were used for the formulation of a mathematical model that permits determination of the parameters of the flashover under uniform or non-uniform pollution of the insulator. The calculated values were found to be in agreement with laboratory tests on artificially polluted insulators. All the experimental techniques use uniform distribution of the pollution layer on the surface of the insulator. Tests on artificially polluted insulators under non-uniform pollution are rare. On the other hand, Rizk measured the deposit of natural pollution on the surface of various insulators for a long period of time. The mathematical model of this work was applied for the calculation of the dielectric strength of the insulator under the determined non-uniform distribution. The type of insulator investigated here is similar to the ones of Rizk. The surface of the insulator is divided into finite elements, uniformly contaminated, across the creepage length. The required parameters for the calculation of the critical voltage for the flashover are the dimensions of the insulator, the arc constants, and the specified distribution of the pollution. The dependence of the critical voltage upon the distribution of the pollution layer and the total pollutant deposit on the insulator are also presented.