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The Partial Discharge Characteristics of PI Film Modified by Nano-Al₂O₃ in Liquid Nitrogen

The polyimide (PI) film is used as the internal insulation system in the high-temperature superconducting transformer due to its excellent mechanical and electrical performance. Many researchers had found that nanoparticle mixing can improve the polymer’s insulation properties. The partial discharge(PD) will induce the deterioration and even breakdown of the insulating materials. In the paper, the PI films modified by nano-A12 O3 were prepared in situ polymerization. The particle size of Al2 O3 nanoparticle used in this research is 10 nm, and the mass fraction is 1wt%, 3wt%, 5wt% and 7wt%, respectively. The volume resistivity, surface resistivity and partial discharge initial voltage (PDIV) are measured in liquid nitrogen(LN). The experimental results indicate that adding of 3wt% nanoparticle is the optimum ratio to suppress the PD in the PI films.