Preliminary studies on thermal ageing of alternate dielectric liquids for transformers

Ester based dielectric liquids with attractive environmental and temperature performance draw the attention for those interested in alternate dielectric liquids for transformers. In this paper Breakdown voltage and Spectroscopy analysis of Mineral Oil, Natural Ester and Synthetic Ester and mixture of mineral oil with Synthetic ester has been compared for fresh samples. Trending patterns of these samples at 110°C temperature stressed for duration of 24, 48, 72 and 96 hours in presence of copper-cellulose assembly has been evaluated using visible spectrophotometry. The present paper is the work done till date in investigating the ageing of the above said samples by accelerated thermal stresses in presence of copper and cellulose. Furthermore in this paper, major hypothetical findings of esters by other researchers relating to physiochemical aspects, Operational Aspects, Dielectric Aspects, Thermal aspects have been discussed in detailed. Design and condition monitoring related issues for ester oil filled transformers has been highlighted.