Thermal and Electrical Properties of a Novel 3-Element Mixed Insulation Oil for Power Transformers

Mineral oil has been used in power transformers for more than 100 years. Extensive research has been conducted on mineral oil substitutes in many countries due to the requirements of green energy and environmental protection. Natural esters are good substitutes for mineral oil. They present fire safety, environmental, and insulation ageing advantages over mineral oil. However, natural esters possess high viscosity, high dielectric loss, high acidity, and poor oxidation stability, and these properties require changing the structural design of transformers. In this study, a novel three-element ( mineral, soybean, and palm) mixed insulation oil was successfully developed. This mixed insulation oil combines the advantages of mineral oil and natural esters, and its key parameters satisfy the requirement of IEC 60296:2012. The thermal and electrical properties of the novel three-element mixed insulation oil, including viscosity, heat transfer performance, permittivity, resistivity and breakdown voltage, were studied comprehensively. Comparison of the thermal and electrical properties of the novel mixed insulation oil with those of common mineral oil showed that the former exhibits better performance than the latter and is suitable for use in power transformers.