Analysis of vegetable liquid insulating medium for applications in high voltage transformers

In high voltage transformers, the liquid insulations are used as the insulating medium as well as cooling medium. For the past several decades, the mineral based transformer oil is used traditionally for the purpose of liquid insulations. In the environmental aspect, there are several disadvantages in the mineral oil even though it has better insulating properties. By considering the environmental aspect and insulating properties, the researchers tend to find the alternate insulating fluids for the high voltage applications. In this work, the natural ester based vegetable oils are investigated to analyze the suitability of it as better insulating medium. The different vegetable oils such as mustard oil, olive oil, gingelly oil, groundnut oil, sunflower oil, palm olein oil and rice bran oil are investigated with the measurement of properties like breakdown voltage, flash point, fire point and viscosity. Further analysis are made with the comparison of properties, the fatty acid content and cost of vegetable oils. From the investigations, it is shown that the natural ester based vegetable oils have the potential to replace the traditional mineral oil.