Effect of TiO2 nanoparticles on DC breakdown performance of transformer oil-impregnated pressboard

Transformer oil-based nanofluid-impregnated pressboard (NIP) with TiO 2 nanoparticles has been previously shown to exhibit substantially higher AC breakdown strength than that of pure oil-impregnated pressboard (OIP). In this study, OIP and NIP with TiO 2 nanoparticles were prepared and experiments on DC breakdown strength of were performed. It was found that NIP possesses higher resistance to DC breakdown strength than that of OIP. To reveal the working mechanism, a pulsed electro acoustic (PEA) device was used to measure the space charge accumulation and dissipation characteristics in OIP and NIP. The results show that the density of deep level traps in NIP is visibly reduced owing to the addition of TiO 2 nanoparticles and homopolar space charge accumulation on both sides of NIP is suppressed. Moreover, the charges injected from electrodes into NIP under DC voltage is also restrained owing to the increase of the Schottky potential barrier. Thus, the DC breakdown performance of NIP is considerably improved.