Investigation of the Dielectric Properties of Mineral Oil Blended with Soyabean Oil for Power Transformers

Abstract

The power transformer is critical equipment in the transmission and distribution network that must be managed to ensure uninterrupted power service. Liquid insulation is essential for the proper functioning of the transformer, serving as both a coolant and an insulating medium, influencing the transformer’s durability. Furthermore, the insulating state of a power transformer significantly impacts its reliability. Mineral oil, derived from petroleum crude oil, has been employed as liquid dielectrics for decades due to its superior operating characteristics. However, as resources for mineral oil are depleted, research is undertaken worldwide to identify viable substitutes. Alternate insulating oils are being investigated for better environmental impact, biodegradability, and economics. Researchers across the globe are investigating various combinations of vegetable oil-based natural esters in these domains. In this work, mineral oil is blended with soybean oil in various proportions, and dielectric properties such as dielectric breakdown voltage, viscosity, flash, and fire point are investigated according to international standards. A quantitative comparison is made among various samples, and it is observed that the blended oil sample with an equal proportion of mineral oil and soybean oil exhibits superior dielectric properties compared to the base mineral oil and other samples with different proportions.