采用“晶界特征分布”优化提升变压器铜绕组的抗油硫腐蚀性能研究

Sulfur corrosion phenomenon is one of factors led the insulation failure of oil immersed substation equipment. The resistivity and dielectric loss increased after the deposition and diffusion of corrosion product in oil-paper. This study focused on the method of inhibiting sulfur corrosion which based on copper itself: Based on the optimization of “grain boundary character distribution”, the grain boundary and grain size could be controlled by processing and heat treatment. The sulfur corrosion resistance of copper winding improved as well as mechanical property and conductivity. Then, the sulfur corrosion resistance of copper winding and its effects on insulation properties will be studied under various conditions (temperature、concentration of corrosive sulfur、oxygen etc.), especially under long-term electrical-thermal aging. Meanwhile, the first-principles calculation and molecular dynamics simulations are used to study the formation energy and process of grain boundary transformation. The mechanism for sulfur corrosion resistance of copper winding will be investigated. Through the exprimental results and theoretical analysis in this project, the optimum process and heat treatment parameters will be obtained to improve performance of copper winding. And the mechanism of sulfur corrosion resistance for copper winding will be revealed. The work not only has important academic research values, but also are important to the safe and stable operation for transformer and the entire grid, even for extending the service life of power equipment.

本课题针对一种引发油浸式变电设备中油纸绝缘故障的因素-油硫腐蚀现象，即由于腐蚀产物沉积与扩散导致的绝缘油纸电阻率降低，介损增加的现象，从铜绕组材料本身出发，提出抑制油硫腐蚀方法：采用“晶界特征分布”优化变压器铜绕组加工与热处理工艺，调控晶界与晶粒尺寸，提升其抗油硫腐蚀性能，并同步提升其导电性能和力学性能；并研究在温度、腐蚀性硫浓度、氧气、电场等因素影响，尤其是长期电-热协同老化过程中铜绕组的抗油硫腐蚀性能及其对油纸绝缘特性的影响；同时通过第一性原理和分子动力学计算并模拟晶界转化能量和过程，探索铜绕组抗油硫腐蚀机理。预计通过本项目的试验及理论分析研究结果，获得铜绕组最优加工和热处理工艺，同步提升铜绕组抗油硫腐蚀性能、力学性能和导电性能；揭示铜绕组抗油硫腐蚀机理。研究不但具有重要的理论学术价值，而且对于保证变压器乃至整个电网的安全稳定运行、延长变压器等电气设备的使用寿命具有重要意义。

本项目针对引起油浸式电力设备的油硫腐蚀现象，提出基于晶界特征分布(GBCD)通过优化铜绕组生产工艺中形变和热处理参数，调控绕组内部特殊晶界含量及分布，有效提升绕组的抗腐蚀性能，并同步提升其导电率和力学性能。然后探究了晶界特征分布优化后的绕组在不同影响因素及长时间热、电热联合作用下的抗腐蚀性能及其对油纸绝缘的影响。最后分别从电化学（反应动力学）和反应热力学两个不同角度揭示了晶界特征分布优化绕组抗腐蚀机理。通过研究项目取得主要成果有：.1. 采用晶界特征分布优化变压器铜绕组，在兼顾绕组导电率及力学性能的前提下，获得了绕组抗腐蚀性能优异的形变和热处理工艺参数。探究了绕组形变量、轧制道次、退火温度以及退火时间对绕组晶界特征分布的影响；.2. 研究了晶界特征分布优化绕组在不同影响因素下的抗腐蚀性能及其对油纸绝缘特性的影响。温度的升高、DBDS浓度的增加、氧气的存在以及电场强度的增大并没有加速优化绕组的腐蚀，绝缘油及绝缘纸上铜元素含量相对较低，油纸绝缘性能相对较好；.3. 研究了晶界特征分布优化后绕组在长时间热及交、直流电热联合作用下的抗腐蚀性能及其对油纸绝缘特性的影响。试验结果表明，优化后的绕组随腐蚀时间的延长并没有发生明显的腐蚀，具有优异的抗腐蚀性能，绝缘油和绝缘纸上铜元素含量较低，油纸绝缘性能受腐蚀影响较小；.4. 分别从特殊晶界的分布、反应热力学角度揭示了晶界特征分布优化绕组抗腐蚀的机理。优化后的绕组因具有大量特殊晶界不但降低了绕组界面能，还打断了随机晶界网络结构，阻断了绕组的腐蚀通道；得出优化后的绕组与腐蚀性硫的反应温度为135.2℃，活化能为32557.62J/mol，均高于普通绕组；从而表现出更加优异的抗腐蚀性能。