Electrical Strength of Composite Insulation System for Polyimide Film Based Cellulose Pressboard

Polyimide (PI) film, the best insulation material in the 21st century, is gradually applied in power apparatus, while the cellulose pressboard combined with PI film have been studied scarcely. In this paper, the cellulose pressboard consisted of one 0.05 mm thick overlapping PI film layer, and the electrical properties were tested on these samples. Partial discharge (PD) and AC breakdown tests were performed to study the insulating properties of PI film and pressboards composite system. In addition, the PD inception voltage (PDIV) values, as well as AC breakdown strength values, of the cellulose pressboards and the PI film based pressboards were obtained for different sample types. These breakdown data were analyzed by two-parameter Weibull distribution model. The results show that the electric insulation properties of PI film based cellulose pressboard are better than pure cellulose pressboard owing to the enhancement of dielectric strength and the improvement of the pressboard surface, and the improvement effect is better for oil-immersed pressboard. This study offers a new perspective in insulation structure design of power apparatus.