基于光滑粒子流体动力方法的金属微粒高速碰撞引发真空击穿的机理研究

With development of vacuum switches to miniaturization and power transmission level, vacuum insulation of vacuum switches become a key issue in power swith area. Metal micro-particles on the contact surface would leave a parent contact and be accelerated under a strong electric field. Then these metal micro-particles would impact on the other contact at high-velocity. The metal micro-particles high-velocity impacts would resulting in the formation of the conductive paths, which would lead to vacuum breakdown in the vacuum swithes. Thsu the metal micro-particles high-velocity impacts were the main factors that could trigger the vacuum breakdown in vacuum switches. The objective of this project was to studied the the micro-particles high-velocity impacts phenaomena, based on the smoothed particle hydrodynamics (SPH) and the experiments. Firstly, the contact surface conditions before and after vacuum breakdown, were detected through Scanning Electronic Microscopy (SEM) and Field Emission Current. Secondly, the SPH methode was introduced to the area of vacuum breakdown. The SPH method of the micro-particles high-velocity impacts phenomena was studied. Finally, the dynamic characteristics of the high-velocity impacts under different voltage are simulated by the SPH method. By comparison with experimental results, the applicability of the SPH in the high-velocity impacts between the micro-particles and the electrode is verified. The formation of the conductive paths was analyzed quantitatively. Then the physical mechanism of vacuum breakdown was analyzed on the basis of the metal micro-particle high-velocity impacts.

随着真空开关向小型化和输电等级方向发展，真空绝缘性能成为当前电力开关领域的关键问题。真空开关电极表面广泛存在的金属微粒在强电场的作用下，会脱离母体电极与对面电极发生高速碰撞，可能形成导电通道并引发真空击穿，因此金属微粒高速碰撞是决定真空开关绝缘性能的关键因素。本项目首次提出通过光滑粒子流体动力学(SPH)仿真结合实验验证的方法研究微粒高速碰撞电极现象。首先，通过表面检测结合场致发射电流测量，定量描述微粒高速碰撞的初始状态和终末状态；将SPH方法引入微粒高速碰撞的研究中，分析SPH方法在微粒高速碰撞现象中的数值问题，并从核函数的形式、光滑长度、粒子间距等方面对其进行优化，形成一套针对微观带电系统高速碰撞的仿真方法；最后，通过SPH方法仿真微粒高速碰撞现象，结合初始状态和终末状态的实验结果，验证SPH方法在微粒高速碰撞电极问题中的适用性，定量描述微粒高速碰撞引发真空击穿的物理机理。

真空开关以其诸多优点，如：环境友好、绝缘强度高、使用寿命长、适用于频繁操作等,目前已广泛应用于12kV～40.5kV 的中压配电等级电力设备领域，并逐步向输电等级方向发展。真空开关在高电压的作用下可能引发真空击穿现象，从而导致真空开关绝缘能力的丧失，严重时还会造成真空开关的爆炸，严重危害电力系统安全稳定运行，因此真空绝缘性能成为制约真空开关向输电等级方向发展的瓶颈问题。因此，为了保证真空开关绝缘可靠性，需要深入研究真空开关中真空击穿的产生机理，找到引发真空击穿的关键因素，对于真空开关的发展具有重要的意义。已有研究表明：真空开关电极表面广泛存在的金属微粒在强电场的作用下，会脱离母体电极与对面电极发生高速碰撞，可能形成导电通道并引发真空击穿，因此金属微粒高速碰撞是影响真空开关绝缘性能的关键因素。本项目的研究目标是采用光滑粒子流体动力学(SPH)方法仿真结合实验验证的方法，研究微粒高速碰撞电极现象引发真空击穿问题。首先，通过扫描电子显微镜(SEM)、三维光学轮廓仪、三维形貌测量仪等，对典型电极材料表面微观状态进行了定量检测，从而为电极表面模型的建立提供了依据；基于分形理论和自由表面理论结合电极表面微观形貌的检测，建立了典型电极材料的粗糙表面模型，并通过电场仿真得到了电极表面微观电场分布特性；成功将SPH方法引入金属微粒高速碰撞电极的研究中，并通过SPH方法仿真了在不同电压下金属微粒高速碰撞平板电极现象；通过实验研究了不同电压下电极表面的破坏特性，并对电极表面破坏状态进行了定量检测，从而确定了金属微粒高速碰撞电极的终末状态；基于金属微粒高速碰撞电极的粗糙表面模型，通过SPH方法仿真了不同电压下微粒高速碰撞电极现象，并与终末状态的实验结果进行了对比，明晰了真空间隙中金属微粒与电极的高速碰撞特性，阐释了金属微粒高速碰撞引发真空击穿的物理机理。目前已经发表与本项目直接相关的SCI收录期刊论文6篇、国际会议论文3篇。