EXPERIMENTAL DETERMINATION OF CRITICAL ARC LENGTH FOR AC FLASHOVER OF POLLUTED PORCELAIN DISC INSULATORS

Hadadi C. Mouneswarachar, and Pradipkumar Dixit

Keywords

Arc length, flashover, insulator, mathematical model, pollution,porcelain

Abstract

A flashover phenomenon is achieved through two successive phases: the initiation of a discharge at the surface of the wet insulator and the elongation of the discharge for flashover, if the conditions are favourable. On the other hand, if the partial arcs succeed in covering a critical part of the leakage path, flashover is practically ensured. In the mathematical models developed for calculating the critical flashover voltage, the critical arc length has been determined using the expression L/(n + 1) or having been used two-thirds of the leakage length (L). In the proposed work, the authors’ intentions were to eliminate the use of different critical values of arc length which were model specific and tried to find the critical arc length which should not be model specific but holds good for the modelling of existing and well-accepted profile of the porcelain disc insulators. In this context, experiments were carried out on five porcelain disc insulators at different arc lengths to study the role of the underside and top surface on flashover voltage at different pollution levels. The analysis of the results obtained by elaborative flashover experiments conducted on the five insulators shows that the leakage distance between the pin and the last rib (or the edge of the underside) is the critical distance for flashover to occur.

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