Nanoparticles for next-generation transformer insulating fluids: A review

Transformers are important components in electrical networks and dielectric fluids play a decisive role in the quality of the insulation systems in these transformers. This review focuses on dielectric nanofluids, which in recent years have come to the fore as innovative electrical insulating fluids. In this context, all studies on insulating base fluids and nanoparticle types have discussed in depth the preparation and stabilization of dielectric nanofluids, their dielectric improvement, viscosity changes, thermal conductivity levels, dissipation factors, partial discharge phenomena, physicochemical properties, aging characteristics, and paper-nanofluid interactions. An average improvement of around 21% was found for the level of breakdown voltage as well as for the lightning impulse breakdown voltage. However, the average enhancement value for positive polarity was 20% for dielectric nanofluids, with an average value of around 10% for the increase in viscosity. Thermal conductivity is higher in nanofluids than in base insulating fluids, which somewhat compensates for the negative situation in viscosity, with the average enhancement in thermal conductivity at around 6%. In related studies, among the physicochemical properties of dielectric nanofluids, a remarkable increase (10% on average) was observed in the flash point level. Although not enough studies have been conducted on the interaction of nanofluids with the cellulosic insulation material used in transformers, pioneering experimental studies have given positive results, especially for aging issues. Dielectric nanofluids have many advantages over conventional insulating fluids, and the ongoing application challenges for future studies are also discussed in this review.