A-C loss characteristics of insulating oil during accelerated oxidation tests

Five years ago, the author presented to this Conference a paper entitled “A New Approach to the Analysis of Insulating Liquids”. In addition to presenting theories concerning the behavior of insulating oils, this paper described the Doble Oxidation Test which furnishes information during an accelerated life test that is indicative of the oil quality and its probable service performance by determining the time to the first appearance of sludge or an acidity of .25 KOH/g. Published as a suggested method in the 1958 Annual Report of ASTM Committee D-9, it is currently under study by Committee D-27. A new equally pertinent test which measures power factor has been developed. The combination of both provides information of far greater value than does either test alone.