Dielectric behaviour of polluted porcelain insulators

Abstract

The dielectric behaviour of polluted porcelain insulators is investigated by means of experimental tests and simulation methods. The elaboration of the experimental results, using well known mathematical models of polluted insulators, leads to the identification of the arc constants. It was found out that the arc constants are independent of the insulator type and of the experimental pollution procedure (salt fog or solid layer cool fog method). This allows the formulation of a generalised simulation model of polluted insulators. The critical parameters for the flashover (voltage, current and gradient) are computed by means of the developed model, using only the geometric dimensions of the insulator, the pollution severity and the arc constants. Different types of porcelain insulators are investigated and the variation of the critical parameters upon the density of the pollution layer is determined. The influence of the geometrical dimensions and of the shape of the insulator to the critical parameters is also investigated. Furthermore, analytical relations are defined, between the computed critical parameters and the salt deposit density as well as the dimensions, the shape and the type of the insulator.