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Interface charge is a serious threat to the reliability of oil-paper insulation system in the converter transformer. In the recent researches, it is indicated that the paperboard modified by nano-TiO2 has excellent insulating properties, but the knowledge of interface charge accumulation and decay is still scarce. In this paper, the interface charge accumulation and decay characteristics of the paperboard modified by nano-TiO2 with different mass fractions were analysed under DC and polarity reversal voltage. The amplitude of the DC and polarity reversal voltage was 4kV. It indicates that the additive of nano-TiO2 has an inhibitory effect on the accumulation and decay of interface charge between the paperboard and oil. The decay behaviour of negative polarity is similar to that of positive polarity, and the 5% mass fraction is the best adding ration for the paperboard. What is more, the decay rate of the positive interface charge is faster than that of the negative one. In the polarity reversal experiment, the decay rate decreases with the increasing of the reversal time. This paper can provide a certain guiding significance for the electrical characteristics improvement of oil-immersed transformer insulation.
Inspec keywords: titanium compounds; transformer oil; power transformer insulation
Subjects: Organic insulation; Transformers and reactors; Reliability