动车组车顶高压电缆终端材料特性分析及电-热耦合场仿真研究

Analysis on Properties of High-voltage Cable Terminal Material on Motor Train Unit Roof and Electro-thermal Coupling Field Simulation

动车组运行环境复杂,在电、热、高速气流等多重因素影响下的车顶高压电缆终端绝缘材料性能是影响动车组供电系统安全稳定的重要因素。本研究采用实验分析与仿真计算相结合的方法,测试分析了车顶电缆终端典型绝缘材料的导热性能、玻璃化转变温度和介电性能;通过建立车顶电缆终端电-热耦合仿真模型,分别研究了室温下电缆终端电场分布以及不同环境温度下的电缆终端温度分布。结果表明:三元乙丙橡胶和环氧树脂的导热系数均随着温度的升高而增大,高于80℃时,导热系数随着温度的升高有所减小。室温下,三元乙丙橡胶和环氧树脂的导热系数分别为0.251 W/(m·K)和0.431 W/(m·K)。三元乙丙橡胶的相对介电常数随着温度的升高逐渐减小,从-60℃的3.70减小到100℃的3.28;环氧树脂的相对介电常数随着温度的升高逐渐增大,从-60℃的5.02增大到100℃的5.29,这是由于二者的玻璃化转变温度不同引起的。仿真结果表明:温度引起交流电缆终端的电场变化不大,最大畸变点出现在应力锥根部,其值为3.120 kV/mm;其次电场集中分布在电缆主绝缘,电场强度为2.995 kV/mm。

The operating environment of EMU is complex,under the influences of multiple factors such as electricity,heat,and high-speed airflow,the performance of insulating material for high-voltage cable terminal on the roof is an important factor affecting the safety and stability of power supply system for EMU.In this study,the thermal conductivity,glass transition temperature,and dielectric properties of typical insulating materials for cable terminal on the roof were tested and analyzed by combining experimental analysis with simulation calculation.The electric field distribution at room temperature and the temperature distribution at different ambient temperatures of the cable terminal were studied by establishing an electric-thermal coupling simulation model of the roof cable terminal.The results show that the thermal conductivity of both ethylene-propylene-diene monomer(EPDM)and epoxy resin(EP)increases with the increase of temperature,and decreases with the increase of temperature when the temperature is higher than 80℃.At room temperature,the thermal conductivity of EPDM and EP is 0.251 W/(m·K)and 0.431 W/(m·K),respectively.The dielectric constant of EPDM decreases gradually with the increase of temperature,decreasing from 3.7 at-60℃to 3.28 at 100℃.The dielectric constant of EP increases gradually with the increase of temperature,increasing from 5.02 at-60℃to 5.29 at 100℃,which is due to the difference of their glass transition temperature.The simulation results show that the change of electric field at the terminal of AC cable caused by temperature is small,the maximum distortion point occurs at the root of stress cone,and the electric field is 3.12 kV/mm.The secondary electric field concentrates in the main insulation of cable,and the electric field is 2.9 kV/mm.