Research on Partial Discharge Characteristic of Nano MMT Modified Insulation Pressboard

In order to restrain partial discharge phenomenon of oil-paper insulation in convertor transformer, the nano montmorillonite (MMT) modified pressboards were developed by nano-doping method. The influence of nano modification on dielectric characteristics of modified pressboards were investigated, and their partial discharge characteristics in pin-plane electrode system were also studied. Meanwhile, the inhibition mechanism to partial discharge of nano-modification was analyzed by software simulation, and its impact to breakdown characteristics was verified as well. The measuring results showed that the conductivity rose with the increase of nano-doping content, while the relative permittivity fell firstly and then rose, which reaching the minimum value at 1%. Also, the breakdown strength of modified pressboard at nano doping ratio of 1% is higher than other ratios under DC and AC voltage. Further, the partial discharge inception voltage increases and maximum PD quantity decreases under same voltage level in oil-paper insulation by using nano modified pressboard at this ratio. Moreover, it helps to homogenize the electric field distribution of insulation structure in PD experiment, and finally contributes to the improvement of breakdown characteristics.