面向高海拔空冷发电机防晕性能演化规律的电热耦合研究

Electrothermal Coupling Research on the Evolutionary Law of Anti-Corona Performance for High-Altitude Air-Cooled Generators

摘要

针对高海拔环境易导致大型空冷发电机定子线棒防晕系统出现长期稳定性劣化的工程问题，以额定电压18 kV空冷发电机定子线棒为研究对象，开展面向高海拔定子线棒防晕性能演化规律的系统研究。提出基于电热耦合老化试验的防晕材料抗老化性能表征方法，采用层次分析法筛选并制备多种模拟试样，结合2 000 h大时间尺度电热老化试验，完成防晕材料的最优选型。通过构建电热耦合作用下防晕材料的非线性电阻率模型，基于黑体辐射修正理论建立高精度定子线棒电-热多物理场双向耦合求解方法，利用COMSOL有限元法对定子线棒稳态与瞬态电热特性进行数值仿真分析。实验结果表明：高海拔修正测试中，定子线棒温升显著增大，起晕电压修正测试的最高温度较常规海拔工况提高74.9%，最大电场强度提高11.9%，温度增幅显著高于电场强度变化。仿真结果与实验数据的相对误差低于5%，验证了所建模型与求解方法的准确性。该研究可为高海拔及超高海拔空冷发电机防晕系统优化设计提供理论依据与工程参考。

Abstract

To address the engineering challenge of degraded long-term stability of anti-corona systems for large air-cooled generator stator bars at high altitudes, the stator bars of an 18 kV air-cooled generator were investigated. Systematic research on the evolutionary law of anti-corona performance for stator bars at high altitudes was conducted. A characterization method for the anti-aging performance of anti-corona materials based on electrothermal coupling aging tests was proposed. Various simulated samples were screened and prepared using the analytic hierarchy process (AHP), and the optimal anti-corona material was selected through a long-term electrothermal aging test for 2 000 h. Furthermore, a nonlinear resistivity model of anti-corona materials under electrothermal coupling was constructed. Based on blackbody radiation correction theory, a high-precision bidirectional coupling solution method for the electrothermal multi-physics field of stator bars was developed, and the steady-state and transient electrothermal characteristics were numerically simulated using the COMSOL finite element method. Experimental results demonstrate that in high-altitude correction tests, the temperature rise of stator bars increased significantly. Compared with low-altitude conditions, the maximum temperature measured during the corona onset voltage test increased by 74.9%, whereas the maximum electric field strength increased by 11.9%, indicating that the temperature rise was substantially larger than the change in electric field strength. The relative error between the simulation results and experimental data was observed to be less than 5%, verifying the accuracy of the proposed model and solution method. This research provides a theoretical basis and serves as an engineering reference for the optimal design of anti-corona systems used in air-cooled generators at high and ultra-high altitudes.

关键词

空冷发电机 / 电热老化 / 有限元法 / 双向耦合 / 防晕性能

Key words

air-cooled generator / electrothermal aging / finite element analysis / bidirectional coupling / anti-corona performance

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基金资助

国家自然科学基金资助项目(51977173)

西藏自治区重点研发计划资助项目(XZ202403ZY0036)