Abstract
Polyimide (PI) film is widely used as an insulating material in superconductivity power equipment, due to its excellent insulation properties under extremely low-temperature. In order to study the aging rule and mechanism of PI film under operating conditions, the PI film was subjected to different degrees of electrical aging in liquid nitrogen. The effects of electrical aging on the breakdown performance and trap distribution of PI film insulation were studied by AC breakdown and isothermal surface potential decay (ISPD) measurements. The results show that the AC breakdown field strength of the PI film gradually decreases with the electrical aging time increasing, from 65.84 to 58.56 kV/mm. At the same time, the shallow trap density increases, and the deep trap density decreases.
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