直流电压下SF_6气体中电极覆膜对金属微粒启举的影响机理

为研究直流电场下SF_6气体中低压电极覆膜对金属微粒启举的影响机理,搭建了实验平台并使用高速摄像机记录运动轨迹。实验结果表明,随着SF_6气体压力的增大,微粒启举场强升高,且启举后到达高压电极的时间缩短。基于图像处理获得了微粒的瞬时位移,结合运动力学方程和最小二乘法提出了启举时电荷量的计算方法,微粒电荷量的计算分析表明启举时的电荷量减小。建立了覆膜后金属微粒周围电场分布的理论模型,电场分析表明金属微粒与薄膜间的电场明显增大及表面电荷密度分布的改变,使得金属微粒受到向下的极化作用力。研究认为:电荷量减小和极化作用力向下综合导致金属微粒的启举场强提高;覆膜后局部放电是金属微粒的带电机理;SF_6气体压力增大使得金属微粒发生局部放电的起始场强升高,导致极化作用力增大,需要更高场强发生启举。

Influence Mechanism of Dielectric Coated Electrodes on Metallic Particle Lift-Off in SF6 Gas under DC Voltage

In order to study the influence mechanism of dielectrically coated electrode in SF6 gas under DC electric field on metallic particle lift-off, experimental platform was setup and motion trajectory was recorded by high-speed camera. The experiment results showed that with the increasing of SF6 gas pressures, the lift-off field of metallic particle was increased and the time to reach the high-voltage electrode was shortened. Instantaneous displacement of metallic particle was gained on the basis of image processing and computational method of charge quantity was raised on the combination of dynamics equation and least square method,analyzing of charge quantity showed that the metallic particle's charge quantity decreased. Meanwhile, theoretical analysis model of field distribution around metallic particle under dielectric coated electrode was established, analyzing of electric field indicated that there was a enhance of electric field between coating and metallic particle and a transform of charge density distribution, which leaded to a downward polarization force for metallic particle. Both the decreasing of the electric charge quantity and the downward polarization force result in the increasing of lift-off field. On the whole, this article maintains that partial discharge is the charging mechanism of metallic particle; the enlargement of SF6 gas pressure brings about the raise of initial electric field of partial discharge, causing the increase of downward polarization force with higher electric field to lift-off.