Positive Streamer Characteristic at The Interface of TiO2 Nanofluid/pressboard under Lightning Impulse Voltage

Recent studies have found that the creeping flashover strength of oil-impregnated pressboard can be improved by the modification of nanoparticles. To further explore the modification effect of nanoparticles, this paper studied the effect of TiO2 nanoparticles on the creeping flashover strength of transformer oil-impregnated pressboard and its prebreakdown streamer characteristics under positive lightning impulse voltage. The test results indicate that the creeping flashover voltage is increased by 34.6% with the addition of TiO2 nanoparticles. Furthermore, positive streamer characteristic at the interface of nanofluid/pressboard including shape, propagation length and velocity was greatly changed in the presence of nanoparticles. Streamers at the interface of pure oil/pressboard tend to propagate closely along the pressboard surface with a rapidly increased length. Whereas streamers at the interface of nanofluid/pressboard have more lateral branches extending into the surrounding oil and develop with a much shorter length. This demonstrates that the propagation of positive streamers is dramatically restrained by the addition of TiO2 nanoparticles, resulting in the increase of creeping flashover strength.