Mineral oil based high permittivity CaCu3Ti4O12 (CCTO) nanofluids for power transformer application

Abstract

Power transformer is the heart of the power transmission and distribution in an electrical system and its lifeblood is transformer's insulating oil that acts as an insulation of the transformer. The physical and electrical properties of insulating oil mainly depend on the constituents of insulating oil and the properties of oil can be optimized by introducing nanofluid. Mineral oil based CaCu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> (CCTO) nanofluids with various volume percent of CCTO (0 to 0.05 vol %) have been prepared under ultrasonication. These nanofluids (before ageing) were evaluated for the critical parameters such as AC breakdown voltage (BDV), loss tangent, dielectric permittivity, resistivity, acidity, interfacial tension, flash and fire point as per the procedure outlined in the ASTM and IEC standards. The nanofluids (NF-0 to NF-3) showed improvement in the AC breakdown voltage, tan delta, flash and fire properties. The AC breakdown voltage increased as the CCTO volume percent increase in the mineral oil. The nanofluids were also subjected to accelerated ageing and the critical parameters, evaluated on the aged nanofluids (ANF-0 to ANF-3), were compared with that of fresh nanofluids. The nanofluids do not show any significant change in the viscosity, however, influences on the electrical properties were observed. The improvement in electrical properties can be attributed to the formation of insulating boundaries in nanomaterial which acts as insulation barrier that hinders the breakdown mechanism.