交流电弧微观动态形成机理及影响因素

Microscopic Dynamic Formation Mechanism and Influencing Factors of AC Vacuum Arc

为揭示真空电弧的微观动态形成机理及其影响因素,利用气体动力学模型研究真空断路器触头间的电弧形成过程。采用的数学模型包括电子和正负离子漂移扩散方程、微观粒子的碰撞方程及电场的泊松方程。建立触头间距为10 mm,触头间电压分别为工频交流12 k V和400 V的真空断路器简化模型,通过仿真得到工频真空电弧形成过程和鞘层形成过程的电子密度、平均电子能量及碰撞能量损失分布等各项微观参数的时变规律,并计算电子迁移率、金属蒸气压力和初始电子密度对真空电弧形成过程的影响。仿真结果表明:粒子运动速度差异形成的鞘层是电弧形成的基础;高电压、强电场作用促使电子能量产生轴向集中;电子迁移率及金属蒸气压力影响电弧形成过程;而初始电子密度对真空电弧弧前导电通道形成过程的影响可忽略。

In order to reveal the microcosmic dynamic vacuum arc formation mechanism and its influencing factors,the kinetic theory of the gases model are used to study the formation process of the arc between the vacuum circuit breaker contacts. The drift-diffusionequations of electron and ion, the collision equations of microscopic particles,and the Poisson equations of the electric field are involved in the model. The simplified vacuum circuit breaker model is then established,in which the distance between the contacts is 10 mm and the voltages between contacts are AC 12 k V and 400 V with power frequency separately. By the simulation, the formation processes of the vacuum arc and the sheath with power frequency, and its corresponding timedependent microscopic parameters such as the electron density,average electron energy,and collision energy loss distribution are acquired. The effects on the formation of the vacuum arc produced by electron mobility,metal vapour pressure and initial electron density are also calculated. The simulation results indicate that the sheath formed by different particle velocities is the basis of arc formation. The energy of the electron is axially concentrated by the affection of high voltage and strong electric field. The mobility of electron and the vaporpressure of metal have a great effect on the formation process of the vacuum arc. However,the initial electron density shows ignorable influence on the vacuum arc formation process.