冲击负荷下高速铁路变压器绝缘的热老化机制与寿命评估

The life and reliability of traction transformers have important effects on the safe operation of high-speed railway, and they also influence the national strategy of “Chinese High-speed Railway Going Out”. Traction transformers have been withstood the effects of shock load, which would become more than 2~3 times rated load when the train passes, and it can result in the winding insulation under short-term high temperature frequently, the short-term high temperature exceeds the limit of long-term operating temperature, in addition, the temperature of oil would be relatively low due to the average load is less than 50%. Currently, there is no effective method that can get the remaining life of traction transformers, there are two reasons as follows: firstly, there is no the model of thermal aging that can be used under the shock load conditions, the service life of traction transformers have great different with the designed; secondly, the very uneven rise of temperature lead to the very uneven distribution of insulation aging. This project will carry out the researches around the main line, which is “Dynamic Temperature Field - Aging Mechanism and Models - Mapping Relationships - Life Evaluation”, and this project will solve the following scientific questions: firstly, a dynamic temperature field model will be established which can reflect the coupling relationship of “oil flow - temperature” under shock load conditions, then the temperature rise in the traction transformer will be calculated accurately under the frequent shock load conditions; the thermal aging mechanism of oil-paper under frequent shock load conditions will be studied, then the aging model would be established that applied high-speed railway traction transformer; the last, the mapping relationships will be established which can reflect the relationships of the dielectric response with the insulation status of uneven aging, the remaining life of traction transformers would be gotten based on the established mapping relationships.

牵引变压器的寿命和可靠性对高速铁路安全运行和实施“走出去”国家战略有重要影响。牵引变压器长期承受冲击负荷作用，列车通过时负荷超过2~3倍额定值使得绕组绝缘频繁承受短时高温（可超过允许长期运行温度的上限），平均负荷远不足50%导致油温相对低。由于缺乏冲击负荷下绝缘热老化模型，变压器的使用年限与设计差异大；极不均匀温升造成了极不均匀的绝缘老化分布，目前缺乏判断具有这种特性的高铁变压器绝缘剩余寿命的有效方法。为此本项目拟以“动态温度场—老化机制与模型—映射关系—寿命评估”为主线开展研究，解决如下科学问题：①建立能够反映冲击负荷下“油流—温度”耦合性的动态温度场模型，以准确计算和预测频繁冲击下高铁牵引变压器的内部温升；②揭示频繁冲击负荷下油纸绝缘的热老化机制，以建立高铁牵引变压器绝缘老化模型；③建立极不均匀老化绝缘状态与介电响应之间的映射关系，以较准确评估高铁牵引变压器绝缘的剩余寿命。

其中特点在于：1）频繁冲击负荷下高铁牵引变压器内部动态温度场的研究与建模：构建了牵引变压器温升与油流关联性的试验平台及多物理场耦合数值仿真模型；明确了过负载启动对牵引变压器热点动态温升的影响，提出并验证了利用相对热时间常数用于变压器热点温度计算方法；建立了多倍过负载下变压器内部温升的解析计算模型，提出了适合于多倍过负载下牵引变压器热特性参数解析计算方法；基于智能算法驱动实测数据得到了热点温度动态预测模型，可实现牵引变压器热点温度的动态评估及批量预测；2）牵引变压器油纸绝缘系统老化研究、介电响应及频率响应模型构建：设计了冲击负荷下油纸绝缘加速热老化试验，基于老化动力学方程得到了不均匀热老化油纸绝缘系统老化过程，明确了绝缘纸不均匀热老化造成的水分分布不均匀是影响频域介电响应测试结果的最主要因素，不均匀热老化绝缘纸的老化分布顺序不影响介电响应测试结果，研究了热老化对矿物油浸绝缘纸水分扩散的影响，提出了油纸绝缘系统低频介电响应的模型和参数方程，基于此模型进一步提出了时变温度下油隙频域介电响应测试结果的校正与归算方法，并设计试验验证其有效性；剖析了牵引变压器绕组变形故障并搭建了模拟试验平台，提出了一种改进的变压器频率响应建模及状态分析方法和均质化仿真模型，有效地区分了不同绕组间绝缘状态变化所造成的影响。3）牵引变压器不均匀热老化油纸绝缘的状态诊断与寿命评估：根据试验与仿真结果，得到了油纸绝缘水分含量与介电响应的映射关系，提出了牵引变压器油纸绝缘的寿命评估方法，并设计试验验证其有效性；提取了有效表征绝缘故障的频率响应曲线特征量，利用动态分频段分析和质心偏移分析提出了基于支持向量机的绝缘诊断方法，准确地评估频繁冲击负荷下牵引变压器绝缘状态。研究过程中取得以下成果：培养博士2名、硕士12名，发表SCI论文10篇、EI论文14篇，录用EI论文1篇，授权发明专利21项，老化研究内容支撑了2019年中国铁道学会科学技术一等奖。