电极烧蚀导致的FLTD气体开关绝缘子劣化机理及其绝缘防护研究

FLTD has a wide range of applications in the field of pulsed power technology, but it requires tens of thousands of gas switches operated synchronous on high voltage and high current, it puts forward a very high demand for the switch performance and the life-time. In the switch discharge process, some electrode erosion products attached to the insulator, it would lead to performance degradation and even surface flashover, and seriously affected the device service life-time and stability. Therefore, it is of great significance to study the degradation mechanism of insulators, to optimize the design of insulation protection and to improve the life-time of gas switch. In this project, we take the UV pre-ionization distortion gas switch as the research object, by doing some large current discharge experiments, to research the relationship between insulator degradation and the particle composition and distribution, and to research the relationship between particle distribution regularity and flow direction and velocity. And combined with the characteristics of electrode erosion, construct the metal particles sputtering model in multi field coupling effect of gravity field, electric field, temperature field and gas flow field, to simulate particle sputtering process, and to analysis the theoretical results and the experimental results to modify the sputtering model, and it can provide a theoretical basis for the design of gas switch insulation protection. Finally, optimize the baffle and surface discharge path to enhance the FLTD gas switch insulation protection design, and do the life-time experiments to test the effectiveness of insulation protection measures.

FLTD在脉冲功率技术领域具有广阔的应用前景，但其要求数以万计的气体开关在高压大电流条件下同步运行，这对开关的性能和寿命提出了极高的要求。开关放电时的电极烧蚀产物附着于绝缘子，将导致绝缘子性能劣化甚至是沿面闪络，严重影响了装置的寿命和稳定性，因此在减小开关电极烧蚀的基础上，研究绝缘子的劣化机理，优化绝缘防护设计，提高气体开关寿命具有十分重要的意义。本项目以带紫外预电离场畸变开关为研究对象，拟通过大电流放电实验研究绝缘子劣化程度与粒子成分及其分布规律之间的关系，粒子分布规律与气流方向和速度之间的关系，并结合电极烧蚀特性，构建金属粒子在重力场、电场、温度场、气体流体场的多物理场耦合作用下的溅射模型，模拟粒子溅射过程，与实验结果对比分析后对溅射模型进行修正，为气体开关绝缘防护设计提供理论依据。最后，通过优化屏档、沿面路径等措施加强FLTD气体开关绝缘防护设计，并通过寿命实验检验防护措施的有效性。

FLTD气体开关大电流放电时,伴随着电极烧蚀会产生粒子溅射现象,粒子溅射产物附着于开关绝缘内腔后将导致绝缘子性能劣化甚至是沿面闪络,因此在减小开关电极烧蚀的基础上,研究绝缘子的劣化机理,优化绝缘防护设计,提高气体开关寿命具有十分重要的意义｡.本项目利用有限元仿真软件模拟了气体开关的放电过程,并分析了开关电极的烧蚀模型｡对应用于FLTD的紫外预电离气体开关进行了匀场优化设计,针对电极烧蚀后的粒子溅射现象,设计了一种内绝缘屛挡,可防止溅射物直接喷溅到原开关绝缘内腔,在不影响原开关电场的同时增加了沿面闪络距离,具有较好的绝缘防护效果｡项目执行过程中搭建了气体开关实验的平台,完成了气体开关触发脉冲源的设计和测试,设计了一种具有低抖动的三电极气体陡化开关,通过实验研究了触发电路中原边回路电感､预电离电阻等电路参数对触发脉冲源的影响,对比分析了三电极预电离和两电极自击穿开关的陡化效果,实验结果表明三电极预电离陡化开关的陡化性能更加稳定,在此基础上设计的触发脉冲源的幅值达到-120kV,脉冲前沿为6ns,触发脉冲陡度<1ns，触发脉冲源性能参数指标较高。此外，关于开关电极烧蚀及粒子溅射的实验研究,因目前实验数据较少未进行深入分析,后续将继续完善此部分的工作｡