Thermal stability change of synthetic ester-based transformer oil

Abstract

For good transformer condition assessment it is necessary to determine the condition of insulating materials, both liquid and solid. Transformer is reliable for as long as its insulation system resists deterioration. Therefore, thermal and oxidation stability are important characteristics of transformer oil. It is a measure of oil resistance for decomposition by the influence of oxygen and temperature. Oils with good thermal and oxidation stability retain their characteristics regardless the thermal stress. Because of environmental and safety issues, the use of synthetic ester-based transformer oils is increasing. Although they have been in use in smaller transformers (distributive, traction, …) for decades, limit values for chemical and physical characteristics are still discussed. New methods for thermal stability evaluation can be useful for insulation condition assessment.