电场对绝缘纸中水分扩散特性的影响

水分和电场是绝缘纸老化的两个重要因素。长期以来水分对绝缘纸的老化作用研究都采取宏观试验的方法，而对电场作用的数值模拟主要是采用Ansoft、Ansys、Matlab等电气专业的仿真软件。但这两种方法都不能反映材料的微观物化过程。本文采用材料分析软件Material Studio分别对不同电场作用下绝缘纸晶面及无定形区的水分的扩散进行了分子动力学模拟。研究结果表明:电场的极化作用会束缚水分子在绝缘纸晶区表面的扩散，使其扩散系数减小，并表现出在X、Y和Z方向的差异性；电场还会使纤维素晶面和水分子的相互作用能增加，纤维素亲水性增强，这在一定程度上影响水分扩散系数的方向性。相比较而言，水分在纤维素无定形区的运动受电场影响规律性较差。

Impact of Electric Field on the Moisture Diffusion Properties of Insulation Paper

Moisture and electric field are two of the most important factors for aging of insulation paper. For a long time, effect of moisture on the insulation paper is mostly based on macro test. Meanwhile, the numerical simulation of the electric field is based on some electrical professional software such as Ansoft, Ansys, Matlab and so on. However, these two methods can not reflect the microcosmic physical and chemical processes of the material at the molecular level. In this paper, moisture diffusions on the crystalline surface and in amorphous region of transformer insulation paper under different external electric field were dynamic simulated respectively by the material analysis software Material Studio. Results show that:The polarization effect of electric field restrains movement of water molecules on the surface of the crystal cellulose, which leads to the reduction of total diffusion coefficient D and the difference among Dx, Dy and Dz. The interaction energy between crystal cellulose surface and water molecules would be increased by electric field, which enhances the hydrophilicity of crystal cellulose surface and affects the directionality of water diffusion coefficient to some extent. Relatively, movement of water in amorphous cellulose with electric field is complicated and lack of regularity.