Abstract

The power transformer is a critical equipment in the transmission and distri- bution network that must be managed to ensure uninterrupted power service. The liquid insulation is essential for the proper functioning of the transformer, as it serves as both coolant and insulating medium, which influences the trans- former’s durability. Further, the insulating state of a power transformer has a significant impact on its reliability. Mineral oil derived from petroleum crude oil has been employed as liquid dielectrics for decades due to its superior oper- ating characteristics, however as a resource for the same are getting depleted over the years. Research is undertaken across the globe to identify a viable substitute for mineral oil. Further, alternate insulating oils are being investi- gated for better environmental impact, biodegradability and economics. Sev- eral combinations of vegetable oil based natural esters are being investigated by researchers across the globe in these domains.  In this work,  mineral oil  is blended with soyabean oil with various proportions and dielectric proper- ties like dielectric breakdown voltage, viscosity, flash and fire point have been investigated according to international standards. A quantitative comparison is made among various samples and is observed that the blended oil sample of equal proportion of mineral oil and soyabean oil exhibits superior dielec- tric properties compared to the base mineral oil and other samples of different proportions.