Comparison of streamers in mineral and synthetic insulating oils with electrical treeing in solids

This paper deals with study of the breakdown and prebreakdown behavior of two mineral based and a silicone oil carried out using uniform and non-uniform electrode geometries under power frequency voltage. The results show that the probability of occurrence of breakdown in mineral based oil under negative polarity is much higher than in silicone oil. The differences in the pre-breakdown streamers in both oils using shadowgraphic optical technique are investigated. Though the shape of the streamers observed are found to be similar to those reported here and in literature for solid olefinic insulations, yet the two phenomena differ considerably in time scale and underlying physical details. The influence of the investigated parameters related to the chemical nature of two oils and polymeric solids are discussed.