大型发电机定子线棒端部防晕结构温度和电场分布仿真研究

大型发电机定子线棒端部防晕层温度和电场分布是表征防晕结构性能的重要参数,关系着发电机的长期安全稳定运行。工频电气试验过程中,防晕材料的电导损耗是线棒端部绝缘温度梯度分布的主要原因,电场分布取决于防晕层电导和主绝缘电容,而电导率又是电场强度的函数,因此发电机定子线棒端部防晕结构温度场和电场的计算是一个相互耦合的过程。本文借助COMSOL Multiphysics有限元分析软件多物理场仿真功能,以某大型水氢冷发电机定子线棒端部防晕结构作为研究对象,仿真分析了其工频状况下的电场分布情况和时域条件下的温度场分布情况,以匹配线棒端部防晕结构设计开发过程。将仿真温度场结果与真机线棒试验结果对比,两者吻合较好,为进一步优化设计防晕结构和材料参数奠定了基础。

The Electric-thermal Field Simulations Study of End Corona Protection Structure on Stator Bar for Large Generators

Temperature and electric field distributions of the end of the stator bar are important parameters to characterize performance of the end corona protection systems(ECP),which has a great impact on the safety and stable long-term operation of the large generator.During the hi-pot test,the conductivity loss of the corona-proof material is the main cause for the temperature gradient distribution of the insulation at ECP area.The resistance of the ECP layer and the capacitance of the main insulation determine the distribution of electric potential along the surface of the bar end,while the resistance of the ECP layer is also a function of electric field strength.So the computation of temperature and electric field is a mutual coupling process.In this paper,with the help of the multiphysics simulation function of the COMSOL Multiphysics,the ECP structure of the stator bar end of a large water-hydrogen cooled generator is taken as the study object for the calculation of the electric field distribution under the power frequency and the calculation of the temperature field distribution under the time domain to match the design and development process of ECP structure at the bar end.Comparing the temperature field distribution from the simulation and the real bar test,the results agree quite well,which lays the foundation for further optimization of the design of ECP structure and material parameters.