(546p) Studies on the Oxidative Stability of Mineral Naphthenic Oils Using Commercial Antioxidants

Mineral naphthenic oil is normally used in transformers, circuit breakers and other electrical equipment for insulating and cooling functions. Due to their usage conditions, it may be subjected to oxidation reactions caused by the presence of oxygen, water and metals, affecting the oil performance. Using the ASTM D2440 method, oxidation studies were carried out on insulating oil, using commercial antioxidants, to assess and compare their thermal oxidative stability, monitored by FTIR analysis, total acid number and sludge content on the oxidized samples. Furthermore, combinations of antioxidants and metal passivators were evaluated to seek the best concentrations that could be used to improve the stability of the insulating naphthenic oil.