Simulated Service Aging Tests of Insulating Oils in Transformers

Five different oxidation-inhibited oils and one non-inhibited oil were subjected to more than ten years of simulated service aging tests in 10-kVA transformers. The oils were aged in six conservator-type and four sealed gas-blanketed transformers. The purpose of these studies was to determine the performance of these oils in oxidation-protected transformers. All the oils remained serviceable throughout the 10-year aging period, but showed marked differences in quality in the final test period during which six of the transformers were opened and operated as free-breathing transformers.