Effect of electron shallow trap on breakdown performance of transformer oil-based nanofluids

Transformer oil-based nanofluids with TiO2 semiconductive nanoparticles exhibit substantially higher AC and positive impulse breakdown voltage levels than that of pure transformer oils. Thermally stimulated current method (TSC) and pulse electroacoustic technique (PEA) have been used to measure charge trap and transportation characteristics of pure oils and nanofluids. It is found that electron shallow trap density and charge decay rate are greatly increased in nanofluids, i.e., fast electrons may be converted to slow electrons by electron trapping and de-trapping in shallow traps of nanofluids, resulting in improved breakdown performance compared to that of pure oil. (C) 2011 American Institute of Physics.[doi:10.1063/1.3660783]