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 TiO₂ nanoparticles 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 TiO₂ nanoparticles 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 TiO₂ nanoparticles. It reveals that the space charge dissipation rate at the surface of NPs is much faster than that of OPs. Moreover, TiO₂ nanoparticles 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.