中文摘要：

提出了一种变插入层电导率和介电常数的三层（A-B-A）绝缘结构。分析了插入层（A）电导率和介电常数对三层绝缘结构真空-绝缘子-阴极三结合点处和真空-插入层绝缘子（A）-主绝缘子（B）三结合点处电场的影响,结果发现通过控制插入层电导率和介电常数可以有效降低真空-绝缘子-阴极三结合点处的电场又不至于使真空-插入层绝缘子-主绝缘子三结合点处电场过高。考虑了介质表面带电的情况,分析插入层介质表面带不同极性电荷对真空-绝缘子-阴极和真空-插入层绝缘子-主绝缘子两个三结合点电场分布的影响。估计了三层绝缘结构真空沿面闪络电压的变化趋势,发现在插入层电导率或介电常数不断增大时,真空沿面闪络电压会呈现先上升后下降,最后趋于稳定。

英文摘要：

An A-B-A insulation structure is proposed to improve the characteristics of surface flashover in vacuum by adjusting the conductivity and permittivity of layer A.According to the electric field theory of series dielectrics,the DC and pulsed field distributions of the structure are calculated and the influences of the conductivity and permittivity of layer A on the electric fields of the vacuum-insulator-cathode triple junction and the vacuum-layer A-layer B triple junction are analyzed.It is found that this structure can effectively reduce,the electric field at the former junction while keep that at the later not too intense.The impact of layer A with different surface charges on the electric field of the two junctions is also analyzed.At last,the variation tendency of surface flashover voltage in vacuum of the A-B-A insulation structure is estimated with continuous change of the conductivity or the permittivity of layer A.