Stabilization of transformer oil against oxidation old practice with renewed interest for preventive maintenance

This paper reviews the mechanism of oil failure due to oxidation, and the detrimental effects on power transformer operation. Also reviewed are the major tests available to diagnose the condition of the transformer oil relative to oxidation stability. Limits are suggested which indicate when oil reclamation or addition of oxidation inhibitor is necessary. An example is given of a representative transformer reclamation service job. Oil property data is presented for the oil conditions before and after several oil reclamation processes.