纳秒脉冲下SF6气体放电特性

随着电力系统电压等级的提高,特快速暂态过电压(very fast transient overvoltage,VFTO)对气体绝缘变电站(gas insulated switchgear,GIS)的安全稳定运行产生了越来越严重的威胁,为了提高设备运行的安全稳定性,促进设备小型化,需要深入分析VFTO下SF6气体的绝缘特性。因而该文利用基于半导体断路开关(SOS)的ns脉冲源SPG 200N的输出电压模拟VFTO波形的快速上升过程,黄铜板-板电极模拟GIS内的均匀场,研究了ns脉冲下SF6气体的放电特性,得到了重频耐受时间、施加脉冲个数等与重复频率的关系。实验结果表明,重频耐受时间随着脉冲重复频率的提高而降低,但击穿前所施加的ns脉冲个数与重复频率的关系比较复杂。随着气压的升高,临界击穿场强与气压的比值E/p有所下降,但在该文研究范围内其值仍高于理想状态下稳态电压对应的单位气压下临界值88.5kV/(mm.MPa)。获得的SF6放电特性为进一步明确VFTO下SF6气体的放电机理提供了实验依据。

Breakdown Characteristics in Compressed SF6 Under Nanosecond-pulses

Very fast transient overvoltages(VFTO) might result in insulation failures inside or outside gas insulated switchgears(GIS),especially in higher voltage levels.For improving the equipment operation security and stability,or for promoting the miniaturization of the equipment,the insulation characteristics of SF6 under VFTO should be analyzed in detail.Therefore,a nanosecond SOS-based pulse generator SPG 200N was used to generate nanosecond-pulses which imitated the fast rising progress of VFTO waveforms,and the copper plane-plane electrodes were used to simulate the uniform field.Moreover,the relationships among repetitive pulse stressing time,number of applied pulses to breakdown,and the repetition rates of the power source were presented.The experimental results showed that the repetitive pulse stressing time decreased with the increasing of pulse repetition frequency.However,the number of applied pulses to breakdown had a complicated varying tendency.It was also shown that the ratio of critical breakdown strength to pressure E/p had a slight decline along with the higher gas pressure,but it was not lower than 88.5 kV/(mm·MPa) within research scope,which was obtained under the steady voltage.The obtain discharge characteristics may be provided as an experimental basis for further clearing the gas discharge mechanism of SF6 under VFTO.