表征变压器绕组热点纸绝缘老化的乙醇特征量及其生成机理研究

The aging state of the cellulose insulation paper determines the insulation life of a transformer; especially the winding hot spot is the "weak" part of the insulation aging. The existing aging characteristics can only reflect the average aging condition of the transformer paper insulation, but cannot characterize the aging state of the winding hot paper insulation. For the first time, the project focused on the relationship between high-temperature rapid degradation of winding hot-spot insulating paper and the produced ethanol. First, the method of reaction molecular dynamics simulation and phase analysis is used to reveal the mechanism of ethanol formation under the conditions of normal aging and high temperature aging of hotspot. Then, through the detection and analysis of the ethanol and its oil-paper equilibrium distribution characteristics, the equilibrium distribution and migration law between oil and paper are discovered to eliminate the influence of non-aging factors on the dissolved ethanol content in oil. In addition, combined with the kinetic theory of cellulose degradation and the non-uniform aging experiment, the quantitative relationship between the ethanol content in the oil and the polymerization degree of winding hotspot insulating paper is established. Finally, the characterization method of winding hotspot paper aging based on the ethanol content is proposed. The project will provide a novel idea for transformers to evaluate the aging condition of paper insulation without power outage, and can provide experimental guidance and theoretical support for the assessment of the weak part of winding paper insulation aging.

纤维素绝缘纸的老化状态决定了变压器的绝缘寿命，而绕组热点处是绝缘老化的“薄弱”部位。现有的老化特征量仅能反映变压器纸绝缘的平均老化情况，无法表征绕组热点纸绝缘的老化状态。本项目首次聚焦绕组热点绝缘纸高温快速降解与产生乙醇的关系，首先综合运用反应分子动力学模拟和物相分析的方法，揭示绝缘纸纤维素的正常老化和热点高温老化降解产生乙醇的机理；其次，通过对乙醇的检测分析及油-纸平衡分布特性研究，挖掘其在油-纸间的平衡分布及迁移规律，消除非老化因素对油中溶解乙醇含量的影响；最后，结合纤维素降解的动力学理论和不均匀老化试验，建立油中乙醇含量与绕组热点绝缘纸聚合度的量化关系，构建基于乙醇特征量的绕组热点纸绝缘老化表征方法。项目成果为变压器提供一种不停电评估纸绝缘老化的新思路，为变压器绕组纸绝缘老化薄弱位置评估提供试验指导和理论支持。

本项目面向大型电力变压器绕组纸绝缘老化薄弱处状态评估的技术瓶颈和实际需求，开展了表征绕组热点纸绝缘老化的乙醇新特征量及其生成机理研究，主要完成的工作包括：1）开展了绝缘纸纤维素老化降解的反应分子动力学模拟研究，获得了纤维素老化降解过程中主要产物分布和生成路径，并明确了纤维素在热应力和电-热复合应力作用下降解生成 LGA 中间产物和产生乙醇的主要反应机理和途径。2）采用气-质联用分析方法研究了纤维素、纤维二糖及中间产物LGA 热解的主要产物成分分布及生成乙醇特征量随老化温度的变化规律，获得了纤维素正常老化和热点高温老化降解生成乙醇产物的反应过程和条件。3）通过搭建油纸绝缘老化测试实验平台，制定了项目研究的具体实验方案，探究了绝缘油和绝缘纸中乙醇等低分子醇类的检测优化分析方法，揭示了油-纸中乙醇含量与纸绝缘老化程度的变化规律。4）以不同老化因素作为研究自变量，明晰了温度、水分和老化程度对油-纸中乙醇含量的影响，建立了温度、水分和老化程度对乙醇在油-纸间平衡分布综合影响的多元回归模型并开展了有效性检验，掌握了乙醇在油-纸间的平衡分布比例及迁移规律。5）开展了变压器绕组热点纸绝缘不均匀老化的试验研究，分析了绝缘纸聚合度沿绕组高度温度场的分布规律，获得了油中乙醇含量与绕组不均匀老化状态下纸绝缘聚合度分布的关系，确定了油中乙醇含量与绕组热点区域绝缘纸聚合度的量化模型。本项目研究成果基于乙醇新特征量为实现变压器绕组纸绝缘老化薄弱位置评估提供了新的理论基础和解决方案，有助于及时掌握运行变压器潜在的绝缘老化缺陷和风险，相关研究成果为该技术在变压器绝缘状态评估领域的应用提供了可靠科学理论与技术支持。