Effect of electric arc on dielectric characteristic and dissolved gases of mineral oil

Abstract

Arcing is one of the most dangerous faults in a power transformer because it release large amount of energy. Arcing result in scission in chemical bonds of hqurd insulation and afterward the recombination of those broken bonds create solid contaminants such as carbon oxides and gases. The appearance of these substances enhances the degradation of the liquid insulation. In long term it may cause failure. This study reports the experimental results on the effects of electric arc on dielectric characteristics such as breakdown voltage, resistivity, dissipation factor and dissolved gases in mineral transformer oil. The electric arc was generated using multi needles-plane electrode system under AC applied voltage with frequency of 50 Hz. The arc magnitude was adjusted using different gap between electrodes. The amount of arc energy was also adjusted by using different arcing period from 0-30 min. The experimental results indicated that breakdown voltage significantly reduced by applying electric arc. Similar behavior was observed for oil resistivity. The arc application enhanced the dielectric losses factor (tan 5). Very small change was observed on dielectric constant. © Medwell Journals, 2011.