非平衡态SF6等离子体弛豫特性研究

摘要

This paper solved the Fokker-Planck dynamic equation which describing the collision process of charged particles from the view of plasma dynamics, the slowing down frequency, deflection frequency, parallel diffusion frequency and kinetic energy exchange frequency of electron in the non-equilibrium SF6arc plasma were obtained. All these parameters were used to analyze the ability of electron velocity slowing, kinetic energy dissipation and kinetic energy exchange between electrons and heavy particles during the collision process. Then though calculated the energy change rate between particles, the time to reach the temperature balance between electrons, heavy particles, electrons and heavy particles due to collision were got. The calculating results show that, the transition time required from non-equilibrium to equilibrium state for SF6plasma should be characterized by the temperature equilibrium time between electrons and heavy particles. When the SF6gas is in the critical state, the boundary between insulating medium and conductive channel, whose temperature is about 3 500~4 000 K, the transition time from non-equilibrium to equilibrium state is about 9.5~535.9 μs, under the pressure of 0.1~2.0 MPa. It is very difficult to reach the equilibrium state for non-equilibrium SF6plasma, which is during the dielectric recovery process in SF6 circuit breaker or during repeated re-ignition process in disconnector.%从等离子体动力学的角度出发,求解描述带电粒子碰撞过程的 Fokker-Planck 动力学方程,计算非平衡态下SF6等离子体中电子的慢化频率、偏转频率、平行扩散频率和动能交换频率,分析了电子速度减慢、动能耗散以及电子与重粒子间动能传递的能力;求解粒子间能量变化率,得到电子-电子、电子-重粒子、重粒子-重粒子间通过碰撞达到温度平衡所用的时间.研究结果表明:SF6等离子体由非平衡态向平衡态过渡所需的时间应该采用电子-重粒子间的温度平衡时间表征,压强0.1~2.0 MPa下,当SF6气体处于绝缘介质和导电通道临界状态时(等离子体温度3500~4000 K),SF6等离子体由非平衡态过渡到平衡态所用的时间在9.5~535.9 μs;高压SF6断路器介质恢复(热恢复过程持续时间10 μs左右)和隔离开关多次重燃(单次燃弧持续时间小于10 μs)等过程中的非平衡态SF6等离子体很难过渡到平衡态.