圆形平板电极与薄膜层叠结构的沿面闪络性能

强电磁脉冲模拟装置中用于脉冲压缩的陡化电容器常采用电极与薄膜介质层叠的结构，其主要绝缘失效模式为沿面闪络。采用圆形平板电极，在SF₆绝缘环境中和加载电压为前沿约30 ns的纳秒脉冲电压的条件下，实验研究了陡化电容器关键结构参数和气压对沿面闪络性能的影响。结果表明:（1）电极厚度、气隙和表面涂覆均不能明显改变层叠结构的沿面闪络电压；（2）气压可以提高层叠结构的沿面闪络性能，但是存在饱和趋势；（3）薄膜介质层数与沿面闪络电压近似线性比例关系；（4）增长薄膜介质伸出长度能显著提高沿面闪络电压。基于流注理论对上述结果进行了探讨，认为极不均匀场中，闪络起始主要由高场强区域决定，但是闪络通道的形成和发展主要由闪络路径上的背景电场决定，因此减小层叠结构三结合点处电场对闪络性能影响不大，但减小闪络通道发展路径上的背景电场，可以有效提高层叠结构的沿面闪络电压。

Flashover characteristics of laminate structure composed of round parallel-plate electrodes and polymer film dielectrics

The peaking capacitor used for pulse compression in electromagnetic pulse(EMP)simulator often uses the laminate structure of electrodes and thin film dielectrics to achieve insulation at high voltage,and the surface flashover is the main insulation failure mode of the peaking capacitor.In this paper,the effect of key structural parameters of the peaking capacitor and the gas pressure on its surface flashover performance were experimentally studied under the condition that the insulation gas was SF6 and the risetime of the applied voltage was approximately 30 ns.The experimental results show that:(1)the electrode thickness,the interspace around the electrodes and the surface coating ceuld not significantly change the surface flashover voltage of the laminated structure;(2)increasing the gas pressure could improve the flashover performance at low gas pressure;(3)the flashover voltage is nearly proportional to the number of polymer film layers;(4)the flashover voltage could be increased remarkably by increasing the extension length of the polymer film dielectrics.Based on the streamer theory,the above results are analyzed and discussed.It is considered that in inhomogeneous field the flashover initiates in the strengthened field region but the formation and development of the flashover channel is mainly determined by the background field on the flashover path.Therefore,reducing the electrical field at the triple point has little effect on the flashover performance but reducing the field on the flashover path can improve the flashover voltage of the laminated structure significantly.