An experimental Investigation of Critical Arc Length for Flashover of Polluted Porcelain Disc Insulators under AC Voltage

Abstract

Porcelain disc insulators are known for their reliability. The design of those newlineinsulators is widely accepted and also acknowledged by reputed international newlinelaboratories. Thus, the present work has not been intended to change the existing profile newlineof the insulator but, intended to eliminate the use of different critical values of arc length newlinein the earlier models which are model specific. newlineIn this regard, experiments have been conducted on real porcelain disc newlineinsulators by varying arc lengths gradually in steps on their polluted surface. This newlinechange or variation of the arc length on the polluted surface has been artificially newlinerepresented by placing a round rod electrode of different lengths on the surface from newlinethe pin to the desired point. Five porcelain disc insulators have been selected for the newlinepresent work. The first four insulators are of standard normal type and the fifth one is newlineAntifog type. The IEC-60507 recommended solid layer method has been used to pollute newlinethe insulators. The four Equivalent Salt Deposit Density (ESDD) levels have been newlineselected to represent low, medium, high and very high pollution levels. The proposed work has been carried out in four phases. The analysis of the results obtained by elaborative flashover experiments newlineconducted on the five insulators shows that the influence of size of arc foot radius on newlineflashover voltage is less significant and single dominant arc leads to the flashover even newlinemultiple arcs have been initiated simultaneously on the polluted surface. The leakage newlinedistance between the pin and the last rib or the edge of the underside of porcelain disc newlineinsulators is the critical distance for the flashover to occur. newlineThis finding helps the designers and researchers in the selection of critical value newlineof an arc length during the predetermination of flashover probability for different newlineservice conditions and for large variety of insulators using mathematical models. This newlinefinding also benefits the utilities during the selection of insulators for different pollution newlineconditions.