Influence of Silica Nanoparticles (SiO2)on Electrical and Physical Properties of Mineral Oil and Vegetable Oils

Abstract

In modern day high voltage applications, the thermal and electrical stress is increasing on transformer because of it’s increased voltage level and reduced size. So dielectric properties of mineral oil need to be improved for high voltage applications. Many researchers have been conducted on the application of nano particle in mineral oil oil for last couple of decades. In recent years researchers have been trying to disperse small concentrations of nanoparticles in mineral oils to improve the electrical and thermal properties. The conventional mineral oil is not environmental friendly because it is not bio-degradable and in future we may run out of mineral oil. So, for the last few years the spotlight is on bio-degradable vegetable oil based transformer insulating fluid as alternative for mineral oil. In this work SiO2 nano particles has been added to modify the vegetable oils like coconut oil and mustard oil as well as mineral oil to study their insulating property. Different concentration of silica nano particles (SiO2) are taken ranging from 0.04 g/L to 3 g/L of the base oil mass. The electrical and physical properties of the vegetable oils have been studied and compared with mineral oil results.The AC breakdown voltage were measured according to IEC60156 standards. It has been found that, the nanofluids have better dielectric properties than pure oil. As we go on increasing the concentration of nanoparticles, the breakdown voltages (BDV) of the oils was increasing but after a certain concentration it start to decrease. It may be because of the fact that at high concentration the nano paricles tend to agglomerate and settle down quickly. But at certain (optimum) concentration of nano particle based oils are showing higher BDV than unmodified mineral oils. Some theories that explains the mechanism of this kind of change of behaviour has also been discussed . This paper also presents the effect of nano particles on refractive index (RI) and viscosity of mineral oil. UV-visible spectroscopy of the samples has also been done to know the change in absorbance of the samples and their qualitative analysis of the samples. It has also been discussed the possible mechanisms for such change of the BDV of the modified oils.