Electrical and acoustic investigation of partial discharges in two types of nanofluids

Abstract

Measurements of partial discharges in liquid dielectrics are important for prediction of a serious failure of electrical equipment. Recent research findings show that application of nanoparticles in dielectric liquids may increase their resistance to partial discharges. However, physical properties of a host liquid are expected to play a decisive role in the effective suppression of partial discharges by nanoparticles. In this paper, a transformer oil prepared by a gas-to-liquid technology and a standard naphthenic transformer oil are doped with an equal amount of iron oxide nanoparticles. Determination of basic physical properties of the oils and the nanofluids is followed by an experimental investigation of partial discharges under various alternating voltage levels. The detection of partial discharges is approached by two independent methods, electrically and acoustically. Both methods revealed occurrence of partial discharges in the gas-to-liquid oil at higher voltages, as compared with the naphthenic oil. Acoustic emission energy is found one order of magnitude greater in the gas-to-liquid oil than in the naphthenic oil. The acoustic wave propagation dependence on the physical properties of the liquid is considered in the qualitative explanation of the observed phenomenon. The presence of nanoparticles can suppress partial discharges in the naphthenic oil, but not in the gas-to-liquid oil.