An Investigation on Stability, Electrical and Thermal Characteristics of Transformer Insulting Oil Nanofluids

Transformer insulating oil nanofluid is made to improve dielectric and thermal properties of oil by employing nanoparticles with proper properties. In the current work, nanofluids based on transformer mineral oil were prepared by three procedures using diamond nanoparticles with high thermal conductivity, as well as high dielectric properties. It was tried to consider the impacts of use of surfactants and ball milling process in the preparation procedures. The effects of a variety of stabilizers (the amount and type) and also the ultrasonic time on diamond nanoparticles’ stability in the oil were investigated and optimized experimentally. Using the optimized nanofluids, thermal conductivity and viscosity of the oil nanofluids were compared and discussed. In addition, the consistency of the thermal conductivity results with Maxwell and also Hamilton and Crosser theoretical models was examined. It was revealed that, the nanofluid preparation procedure, temperature and nanoparticles’ concentration had effects on thermal conductivity of the transformer oil nanofluid, while the presence of nanoparticles had a slight impact on the viscosity of the fluid. Also the effect of presence of diamond nanoparticles on the electrical properties of transformer oil was studied. Based on the experimental results, adding diamond nanoparticles could lead to an increase in the transformer oil breakdown voltage, while it had nearly no effect on dielectric loss at low concentrations.