变压器绝缘纸热老化降解微观机理的分子模拟研究

Molecular Simulation for Thermal Degradative Micromechanism of Power Transformer Insulation Paper

基于原子水平的分子模型模拟分子的结构与行为,将有助于更深刻地分析变压器绝缘纸热降解的各种复杂现象的微观机理。为此,利用分子动力学(MD)方法与密度泛函理论(DFT)建立了绝缘纸纤维素的降解模型。采用COMPASS力场对绝缘纸纤维素分子在热场作用下的微观降解过程进行了分子动力学模拟研究。并结合原子力显微镜(AFM)观测分析了实验的绝缘纸热降解特性。模拟结果表明纤维素分子主链的β-1-4糖苷键连接处最易发生断裂,直接导致其聚合度降低,热对纤维素的降解很大程度上影响了绝缘纸的聚合度水平。分子模拟结果与实验实测结果比较相符。

In order to explore the microscopic mechanism of the transformer insulation paper thermal degradation, the atomic level of molecular model is adopted to simulate the molecule＇s structure and behavior, so that the mecha- nism of various complex phenomena of the transformer insulation paper thermal degradation can b＇e understood more profoundly. Therefore, the molecular dynamics [MD} and density functional theory （DFT） were used to establish the degradation model of cellulose molecule. Adopting COMPASS force field, the microscopic degradation process of insulation paper cellulose molecule,under thermal field environment was studied and analyzed by MD simulation, and the experimental insulation paper was observed by atomic force microscope{AFM}. The result shows that chain fracture of cellulose molecule occurs in the β-1-4 glycosidic linkage, leading to polymerization degree of cellulose decrease. Therefore, the thermal field for degradation of cellulose plays an important role in the level of the polymerization degree of insulation paper . The computational results well accord with the actually observed ones by experiment. Key words： molecular simulation; insulation paper; cellulose; thermal degradation; microscopic process; atomic force microscope