过渡金属对植物油变压器的绝缘老化影响研究

The Effect of Transition Metals on Insulation Aging of Vegetable Oil Transformers

随着对植物油变压器的不断研究,植物油变压器的绝缘老化问题逐渐暴露出来。而过渡金属铜、铁等会在植物油变压器的绝缘老化方面产生不同程度的劣化作用,进而会导致变压器内部绝缘出现故障。因此,基于分子动力学原理,使用MaterialStudio软件从分子层面上研究了过渡金属对植物油变压器的劣化作用,并探讨了铜铁协同劣化作用的机制。从弹性模量、氢键、均方位移、剪切黏度等多个角度逐步探讨产生变压器内部绝缘性下降的微观原因。杨氏模量、体积模量、剪切模量和泊松比等力学性能参数,以及氢键、均方位移、静电能量、剪切黏度等数据表明,过渡金属会对油纸绝缘系统造成不同程度的劣化和老化,且其劣化作用与金属种类和浓度有很大关系,在不同金属浓度下,金属的劣化作用是不一样的。由所建模型的分子动力学仿真计算结果可知,6组不同金属浓度的油纸绝缘复合模型的力学性能相关参数的变化规律显示,铁原子对油纸绝缘复合模型的劣化作用大于铜原子,也大于铜、铁原子协同的劣化作用,三者之间呈现出铁>铜铁>铜的劣化作用强弱规律。纤维素的氢键、均方位移和静电能量的分析数据表明,金属含量的逐渐增加会降低绝缘纸的绝缘性,加速油纸绝缘系统的老化。其分子模拟计算结果显示,当金属质量分数为16.61%(较低浓度)时,几种混合模型对纤维素分子结构破坏作用相差不大;当金属质量分数为27.38%(较高浓度)时,油纸铜模型对纤维素分子结构的破化作用较大。从绝缘油的剪切黏度分析结果可知,其剪黏度随金属物质浓度的增加呈减小趋势,三种含金属模型对绝缘油呈现出铁>铜铁>铜的劣化强弱规律。由分子动力学模拟的结果可知,铁原子对油纸绝缘复合模型的总体劣化作用大于同等条件下的铜原子。实际应用时,由于油纸绝缘系统中铁的含量要远远低于铜的含量,所以呈现出铜的总体劣化作用更大。硅钢片中其他元素增强了铁的抗氧化性,且硅钢片是由铜导线缠绕,其与绝缘油和绝缘纸的接触面积减少,种种原因致使油纸绝缘系统的铜的含量远远大于铁的含量。所以,控制好过渡金属在油纸绝缘系统中的比例对于预测和延长变压器的使用寿命有非常重要的实际意义。研究结论是,不同过渡金属在不同浓度下对植物油变压器的油纸绝缘系统的劣化程度是不一样的。根据分子动力学模拟结果可知,对油纸绝缘复合模型而言,铁原子的劣化作用显著大于铜原子,这导致了铜、铁原子协同的劣化作用要大于单独铜原子的劣化作用。该结论为延长变压器的使用寿命提供了仿真理论依据。

With the continuous research on vegetable oil transformers,the insulation aging problem of vegetable oil transformers is gradually exposed.The transition metal such as copper and iron will have different degrees of deterioration in the insulation aging of vegetable oil transformer,which will lead to internal insulation failure of transformer.Therefore,based on the principle of molecular dynamics,Material Studio software was used to study the corrosion degradation effect of transition metals on vegetable oil transformers at the molecular level,and the mechanism of copper-iron synergistic degradation was discussed.From the elastic modulus,hydrogen bond,mean square displacement,shear viscosity and other aspects,the micro reasons for the decrease of internal insulation of transformer are discussed.The Young’s modulus,bulk modulus,shear modulus,Poisson’s ratio and other mechanical property pa⁃rameters,as well as hydrogen bond,MSD(Mean Square Displacement),shear viscosity and other data show that the transition metal will cause different degrees of deterioration and aging of oil-paper insulation system,and this effect is closely related to the type and concentration of metal.Under different metal concentrations,the degradation of metal is different.According to the molecular dynamics simulation results of the model,the varia⁃tion rules of mechanical properties parameters of 6 groups of oil-paper insulation composite models with differ⁃ent metal concentrations show that,the degradation effect of iron atoms on oil-paper insulation composite model is greater than that of copper atoms,and also greater than that of copper&iron atoms.The degradation effect of iron>copper&iron>copper is form strong to weak.The analysis data of hydrogen bond,mean orientation shift and electrostatic energy of cellulose show that the gradual increase of metal content will reduce the insula⁃tion property of insulating paper and accelerate the aging of oil-paper insulating system.Its results of molecular simulation shows that,there is a little difference in the damage effect of the mixed models on the molecular struc⁃ture of cellulose when the metal mass fraction is 16.61%(low concentration).When the metal mass fraction is 27.38%(high concentration),the oil-paper-copper model had a greater effect on cellulose molecular structure then other models.From the shear viscosity analysis results of insulated oil,it can be seen that the shear viscosi⁃ty decreases with the increase of metal concentration.The three metal-containing models show the regularities of iron>copper&iron>copper deterioration for insulated oil.The results of molecular dynamics simulation show that the overall degradation of iron atoms on the oil-paper composite model is greater than that of copper atoms under the same conditions.In practical application,because the content of iron in oil-paper insulation sys⁃tem is much lower than that of copper,the overall deterioration of copper is greater.Other elements in the silicon steel sheet enhance the oxidation resistance of iron,and the silicon steel sheet is wound by copper wire,and its contact area with insulating oil and insulating paper is reduced.For various reasons,the content of copper in the oil-paper insulation system is far greater than that of iron.Therefore,it is of great practical significance to con⁃trol the proportion of transition metals in oil-paper insulation system for predicting and prolonging the service life of transformers.The research conclusion is that the degradation degree of different transition metals in different concentra⁃tions of vegetable oil transformer oil-paper insulation system is different.The degradation effect of iron atoms is significantly greater than that of copper atoms,resulting in the synergistic degradation of copper&iron atoms is greater than that of copper atoms alone.This provides a simulation theoretical basis for extending the service life of the transformer.