The Polyimide (PI) film, as an excellent insulating material, is broadly utilized in superconductivity power equipment, especially under low temperature. There is an enormous influence on the breakdown performance of polymers because of the presence of surface and space charge. In order to investigate the electrical aging impact on breakdown and trap characteristics of PI films with 0.1 mm and 0.125 mm thickness, the samples suffer from diverse degrees of electrical aging in liquid nitrogen (LN2). The insulation strength test has been carried out on the PI film samples under different electrical aging stages in LN2. The isothermal surface potential decay (ISPD) method is performed on the PI films to explore the behaviors of trapped charges, and the trap characteristics of the PI films are obtained. Those results indicate that the breakdown strength of the thinner PI film (0.1 mm) in LN2 is higher than that of the thicker one (0.125 mm), and the breakdown field strength reduces with the electrical aging time increasing. The ISPD measurement results indicate that the average decay rate of surface potential in the 0.125 mm PI is faster than the other thickness during the whole decay process.

中文翻译：

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电老化对不同厚度聚酰亚胺薄膜在液氮中击穿和电荷陷阱特性的影响


聚酰亚胺（PI）薄膜作为一种优良的绝缘材料，广泛应用于超导电力设备，特别是在低温下。由于表面和空间电荷的存在，对聚合物的击穿性能有巨大影响。为了研究电老化对0.1 mm和0.125 mm厚度的PI薄膜击穿和陷阱特性的影响，样品在液氮（LN2）中进行了不同程度的电老化。对不同电老化阶段的PI薄膜样品在液氮中进行了绝缘强度测试。对PI薄膜进行等温表面电位衰减（ISPD）方法来探索俘获电荷的行为，并获得PI薄膜的陷阱特性。结果表明，LN2 中较薄的 PI 薄膜（0.1 mm）的击穿强度高于较厚的 PI 薄膜（0.125 mm）的击穿强度，且击穿场强随着电老化时间的增加而降低。 ISPD测量结果表明，在整个衰减过程中，0.125 mm PI的表面电势平均衰减速率比其他厚度更快。