高速气流环境绝缘子表面电荷积聚特性及其场强畸变效应的研究

The flashover of roof outdoor insulation is one of the reasons that influence the safety operation of high-speed train. Contamination particles deposited on roof insulator in high-speed aerosol with the property of non-uniform distribution, non-long-term accumulation and contains metallic powder and sand dust which are easy to carry charges. The turbulent boundary layer is an significant factor which affects particle charging property and its movement mechanism on insulator surface. Charge accumulation may occur at the near of metallic particles which will generate non-uniform distribution of surface charge, then leads to electric field distortion because of the frequent impulse overvoltage applied on high-speed train devices. Field distortion rate and the dynamic variation property of surface electric field are the main factors that influence flashover voltage of insulator. The trajectory of charge particle was studied based on the analysis of triboelectrification characteristics between particle to particle and particle to insulator surface. Surface charge distribution regularity on insulator was established through the analysis of the charge accumulation characteristic of surface metallic particle under electric field. The influence of charge accumulation to field distortion effect was analyzed, then criterion of critical flashover electric field and the relationship between surface electric field distribution regularity and flashover characteristic were established. This project illuminated flashover mechanism of insulator in high-speed aerosol and improved the service performance of insulator which established the foundation of safety operation of high-speed train.

车顶外绝缘闪络是影响高速列车安全运行的主要原因之一。高速气流环境中车顶绝缘子表面的污秽颗粒具有不均匀分布、非长期积累、含有金属性粉尘及沙尘等易带电荷物质的特征。高速湍流边界层是影响颗粒带电特性及其在绝缘子表面的运动机制的重要原因。受高速铁路频繁的冲击过电压影响，车顶绝缘子表面的金属颗粒附近还会产生电荷积聚，造成表面电荷不均匀分布，导致表面场强畸变。场强畸变率与表面场强的动态变化特性是影响绝缘子闪络的主要因素。因此，本项目通过对高速气流下颗粒间及颗粒与绝缘表面间摩擦带电特性的分析，研究带电颗粒的运动轨迹；分析电场作用下表面金属颗粒的电荷积聚特性，建立绝缘子表面电荷分布规律；分析电荷积聚对表面场强畸变效应的影响，建立临闪场强评判标准、表面场强分布规律与闪络特性的关系，为阐明高速气流下绝缘子闪络机理，提高绝缘子服役性能，保障高速列车的安全运营奠定基础。

车顶外绝缘闪络是影响高速列车安全运行的主要原因之一。高速气流环境中车顶绝缘子表面的污秽颗粒具有不均匀分布、非长期积累、含有金属性粉尘及沙尘等易带电荷物质的特征。列车在运行过程中可能发生闪络放电，车顶绝缘子表面沉积的带电颗粒会产生电荷积聚，造成表面电荷不均匀分布，导致表面场强畸变，影响绝缘闪络的发生发展进程。因此，本项目研究了高速气流环境下车顶绝缘子积污特性，建立了高速气流环境车顶绝缘子空间带电微粒运动与沉积模型，探明了高速气流环境车顶绝缘子污秽运动规律及分布特性，并通过试验模拟验证了模型的有效性，解决了高速气流环境下车顶绝缘子空间带电微粒运动及动态沉积问题；同时，试验研究了金属颗粒对绝缘表面电荷积聚的影响特性，获得了高速气流下绝缘表面电荷分布规律，揭示了金属颗粒与绝缘表面电荷动态分布的作用机理，试验探究了不同金属颗粒位置、大小及形状对闪络电压的影响，探明了金属颗粒及表面电荷对闪络电压的综合影响机制；搭建了高速风洞试验系统及沙尘荷质比测量装置，实现了动车组车顶绝缘子所处空间沙尘环境的模拟和电荷测量。以环氧树脂绝缘子为研究对象，开展了在有风无沙、风沙流不带电和风沙流带电三种不同环境下绝缘子闪络试验，分析了风速、沙粒粒径、沙尘荷质比等因素对绝缘子闪络特性的影响规律，并结合试验与仿真结果探索了不同影响因子对绝缘子闪络电压的影响机理。研究工作可为高速气流污秽环境下的车顶外绝缘防护与设计提供指导，为提高动车做车顶绝缘子服役性能、保障高速列车的安全运营奠定基础。