Statistical analysis of AC dielectric breakdown in transformer oil-based magnetic nanofluids

Abstract

Insulating nanofluids often exhibit better insulating properties than their base liquids. In particular, dielectric breakdown performance of insulating liquids may be remarkably enhanced by the presence of nanoparticles. The purpose of this paper is to demonstrate experimental evidence of the missing enhancing effect of the magnetic nanoparticles dispersed in transformer oil and to find potential reasons for the unimproved AC dielectric breakdown. The research is conducted on a long-term stable magnetic nanofluid with three different volume fractions of iron oxide nanoparticles coated with oleic acid. The AC dielectric breakdown voltage is investigated at various temperatures and statistically treated. Temperature-dependent viscosity, dissipation factor, and AC electric current are presented as supporting experimental results. In searching for the reason of the unimproved dielectric breakdown, we focus on the nanoparticle interface and consider the limited ability of the modified nanoparticles to act as charge trapping centers under the AC dynamic conditions.