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Recent Progress and Challenges in Transformer Oil Nanofluid Development: A Review on Thermal and Electrical Properties

Transformer oil is refined electrical insulating oil, which is extremely stable at high temperatures and possesses excellent electrical insulating properties. These special types of oils are widely used in high voltage apparatus such as power transformers, high voltage capacitors and circuit breakers. Traditionally, mineral oils have been most commonly used as a coolant or as electrical insulation medium. However, the main concern related to mineral oil is overheating, overloading, short circuits that reduce the shelf life of the transformer unit and restrict its function as a reliable coolant. Moreover, other factors such as high electrical insulation requirements, safety and economic aspects need to be considered for the development of new insulating liquid material. Nanofluids have become the one of the alternatives for the existing products available in the market because of its high thermo-physical and good dielectric properties. This review focuses on the status of nanofluids, the effect of different nanoparticles to enhance the dielectric as well as its heat transfer properties of nanofluids. The thermo-physical properties of the newly developed transformer oil based nanofluids reported in comparison with different oils. Finally, future directions and challenges need to be addressed.