Electrical Characteristics of Cellulose Pressboard Modified by Nano-TiO2in Mineral and Vegetable Mixed Oil

Oil-pressboard composite insulation system is the main insulation structure inside oil-immersed transformers. However, the mismatch of relative permittivity between insulation oil and cellulose pressboard is a dominant factor for uneven distribution of electric field. Moreover, the mineral insulation oil used in the transformer dissatisfies environmentally friendly and renewable. In this paper, the electrical characteristics of modified cellulose pressboard in mixed oil were researched. The pressboard modified by nano-TiO
2
and the mixed oil composed of mineral and vegetable oil were prepared in the lab. The modified pressboards were impregnated in pure mineral oil and mixed oil with 10 V%, 20 V% and 30 V% vegetable oil in the vacuum oven, respectively. The experiments, including partial discharge inception voltage (PDIV) and AC breakdown strength, were carried out to characterize the electrical performances of the modified mixed oil-immersed pressboards. The data were discussed on the effect of mixed oil and addition of nano-TiO
2
particles. The investigation results indicate the electrical performance of nano-TiO
2
modified pressboard is better in the mixed oil than that in pure oil. All the preliminary results throw light on promotion and application of the mixed oil in the transformer.