Dispersion behavior and breakdown strength of transformer oil filled with TiO<sub>2</sub> nanoparticles

Abstract

Recently, the study of transformer oil-based nanofluids became of great interest, due to their prospective properties as a dielectric and cooling medium. However, agglomeration of nanoparticles limits the beneficial properties that can be obtained from nanofluids. So, the work presented in this paper aims to get enhanced dispersion behavior of nanoparticles within transformer oil-based nanofluids. Then, breakdown strength with the enhanced dispersion behavior is evaluated. In order to get enhanced dispersion behavior, nanofluids were prepared using nanoparticles with a surfactant. The surfactant plays a role in the stabilization of nanoparticles and maintaining suspension stability. The considered type of nanoparticles is TiO2 nanoparticles. Two series of nanofluid samples were prepared. Through the first series, the effect of surfactant concentration on dispersion behavior and agglomerate size was studied. The dispersion of nanoparticles was characterized using three different techniques. These techniques are optical microscope analysis, transmission electron microscope (TEM) analysis and zeta potential measurements. Based on these techniques, the suitable concentration of surfactant was identified. The second series of nanofluid samples was prepared with different weight percents of nanoparticles for assessing the breakdown strength. Weibull distribution was used to calculate the breakdown probability for the base oil as well as nanofluid samples. The results showed an enhancement in the breakdown strength by about 27% in comparison to the base oil. Based on the obtained results, mechanisms behind the dispersion behavior and breakdown strength were proposed and discussed.