Quality and Performance of Reclaimed Mineral Oils

Dielectric insulating liquids perform multiple critical functions in transformers, but are exposed over time to thermal, oxidative and electrical stresses which can lead to degradation of the liquid. In the case of mineral oils, reclaiming is a well-established method for restoring the oil quality and performance by removing aging by-products and contaminants in a cost and energy efficient manner. This paper presents acidity and interfacial tension measured in Norwegian transformers reclaimed in the late 1990s demonstrating the long-term effectiveness of reclaiming in removing degradation by-products and detrimental contaminations from both transformer oil and cellulose. Furthermore, three recently reclaimed oils and three unused rerefined oils are subjected to acceptance testing for…