Nanoparticle effects on creeping flashover characteristics of oil/pressboard interface

Surface creeping discharge at solid-liquid interface is regarded as one of the reasons for oil-immersed transformers failure. In order to restrain the surface creeping discharge, we investigated the effects of TiO2nanoparticles on creeping discharge and flashover characteristics of the oil/pressboard interface under AC and impulse voltages. Partial discharge and creeping flashover tests of oil/pressboard (OPs) and nanofluid/- pressboard (NPs) were carried out. The results show that TiO2nanoparticles can improve both partial discharge inception voltage (PDIV) and creeping flashover strength of oil-impregnated pressboards. Thermally Stimulated Depolarization Current (TSDC) and Electrostatic probe techniques were used to measure space charge behaviors of oil/pressboard before and after modification of TiO2nanoparticles. It reveals that the space charge dissipation rate at the surface of NPs is much faster than that of OPs. Moreover, TiO2nanoparticles can greatly increase the shallow trap density and lower the shallow trap energy level of oil-impregnated pressboard. It is believed that electrons may be repeatedly trapped and de-trapped by shallow traps in NPs, which can reduce the accumulation of space charges and result in improving the creeping flashover strength of oil/pressboard interface.