针-板电极下SF_6的电晕放电特性分析

为研究SF_6气体在针-板电极下电晕放电特性,通过建立SF_6气体电晕放电的流体模型,采用有限元-通量校正传输法(finite element method-flux corrected transport,FEM-FCT)对其进行仿真计算,得到负针-正板电极下电晕放电过程中的电子数密度分布以及空间电荷对电场的畸变作用。在此基础上,提出一种SF_6气体电晕起始电压的数值计算方法,对放电过程进行循环迭代求解,计算SF_6气体在不同气体压强、电极间距下的电晕起始电压。通过脉冲电流法开展SF_6电晕放电特性研究,测量负针-正板电极下电晕起始电压,对计算结果进行验证。研究表明:随着电子崩不断向前发展,其头部的电子数密度迅速增长,当气压为0.1 MPa、5 mm绝缘间隙放电4 ns时的电子数密度峰值达到4.85×1015 m–3;放电过程产生的空间电荷将导致外电场畸变,气压为0.1 MPa、5 mm间隙放电4.4 ns时电场强度最大值为30.7 kV/mm;SF_6电晕起始电压随气体压强升高基本呈线性增长、随间距增大而增长缓慢;针板间距5 mm时,计算值由0.1 MPa时19 kV上升到0.6 MPa时的71.4 kV,实验测量值略低于仿真计算值。

Analysis of Corona Discharge Characteristics of SF_6 Under Pin-plate Electrodes

We established and simulated a fluid model of SF6 gas corona discharge by using the FEM-FCT(finite element method-flux corrected transport) method to analyze the characteristics of SF6 gas corona discharge. The distribution of electron number density and distortion effect of space charge on the electric field in the corona discharge process under negative pin-positive plate electrodes were obtained. On this basis, a numerical calculating method for the inception voltage of corona discharge in SF6 gas was proposed. Moreover,the corona inception voltages of SF6 gas under different gas pressure and electrode spacing were calculated through the loop iteration of discharge processes. The corona inception voltage of negative pin-positive plate electrode was measured and the calculation results were verified by using the pulse current method to study the corona discharge characteristics of SF6. Study shows that, with the continuous forward development of electron avalanche, the electron density of the head increases rapidly. The electron density peak value is 4.85×1015 m–3 when gas pressure is 0.1 MPa and the 5 mm insulation gap discharge time is 4 ns. The space charge generated in the discharge process will lead to the distortion of the external electric field, and the maximum electric field strength is 30.7 kV/mm when gas pressure is 0.1 MPa and the 5 mm insulation gap discharge time is 4.4 ns. The corona inception voltage of SF6 increases almost linearly with the increase of gas pressure and increases slowly with the increase of gap. When the pin plate gap is 5 mm, the simulation calculation value increases from 19 kV under 0.1 MPa to 71.4 kV under 0.6 MPa. The experimental values are slightly lower than the simulated values.