PI fiber insulation paper has excellent insulation and heat resistance, which can replace traditional insulation paper to provide a new high-performance material. In this paper, we adopt a two-step method to synthesize PI, that is, firstly synthesize polyamic acid, and then perform electrospinning and thermal imidization to prepare PI porous fiber membrane. The test results show that the breakdown field strength of the PI porous film is 50 kV/mm. Further research shows that the insulation structure has the characteristics of continuous multiple breakdown. When the fiber film is repeatedly broken down to 25 times at the same point, the field strength of each breakdown of the fiber film changes between 40 and 55 kV/mm, and the average breakdown field strength is 53 kV/mm. Nano-Al₂O₃ was introduced into the fiber membrane by in situ polymerization. The breakdown field strength of the composite fiber film can reach 74.89 kV/mm after doping 2 wt% nano-Al₂O₃, which is higher than that of the pure film. At the same time, this kind of fiber paper also has repeatable breakdown characteristics, and the breakdown voltage distribution width of multiple breakdown is reduced. This characteristic provides the maintenance free characteristic of DC over-voltage for the insulation structure composed of this fiber paper, and can improve the service life of transformer under DC over-voltage such as lightning stroke.

PI纤维绝缘纸具有出色的绝缘性和耐热性，可以代替传统的绝缘纸提供一种新型的高性能材料。本文采用两步法合成PI，即首先合成聚酰胺酸，然后进行电纺和热酰亚胺化制备PI多孔纤维膜。试验结果表明，PI多孔膜的击穿场强为50kV / mm。进一步的研究表明，绝缘结构具有连续多次击穿的特性。当在同一点将纤维膜重复击穿至25次时，每次击穿的纤维膜的场强在40到55 kV / mm之间变化，平均击穿场强为53 kV / mm。纳米Al ₂ O ₃通过原位聚合将其引入纤维膜中。掺杂2 wt％的纳米Al ₂ O _3后，复合纤维膜的击穿场强可以达到74.89 kV / mm ，高于纯膜。同时，这种纤维纸还具有可重复的击穿特性，并减小了多次击穿的击穿电压分布宽度。该特性为由该纤维纸构成的绝缘结构提供了直流过电压的免维护特性，并且可以提高变压器在直流过电压（例如雷击）下的使用寿命。