Investigation on the Properties of Natural Esters Blended with Mineral Oil and Pyrolysis Oil as Liquid Insulation for High Voltage Transformers

For the several decades, petroleum-derived mineral oil has been used as liquid insulation due to its better operating properties, low cost and availability. Many research works have been performed over the years to find the potential replacement of traditional mineral oil to overcome its disadvantages such as poor biodegradability, environmental issues and scarcity of availability in future. In these aspects, various vegetable oil-based natural esters are investigated by the researchers throughout the world. With the objective of developing functional efficient liquid insulation for high-voltage transformers, investigation is carried out with natural esters (sunflower oil, rice bran oil, corn oil and olive oil), blended with traditional mineral oil and biomass-based pyrolysis oil. In this work, for ensuring the characteristics of investigating liquid insulation, properties such as breakdown voltage, flash point and viscosity are measured according to international standards. From the investigations, it is found that the natural esters and blended oil samples have the properties as nearer to standard values for liquid insulations used in high-voltage transformers and have the ability to replace traditional mineral oil as alternate liquid insulation.