直流电压下金属微粒对绝缘材料真空沿面耐电性能的影响

Influence of Metal Particle on Surface Flashover Characteristics of Insulating Material Under DC Voltage in Vacuum

表面附着金属微粒是绝缘子发生沿面闪络的重要诱因,研究金属微粒对绝缘材料真空沿面耐电性能的影响对于真空电气设备的研发、生产以及运行等具有重要意义。为此采用对称平面压接电极结构,研究了直流电压下金属微粒尺寸及附着位置对聚四氟乙烯（PTFE）材料沿面闪络电压及表面电荷分布的影响。结果表明：在直流电压下,金属微粒会显著降低材料的闪络电压且粒径越大其降低程度越大,2 mm微粒可使闪络电压下降25%左右;在不同附着位置下,金属微粒靠近阴极时材料闪络电压最高,其次为靠近阳极,中间位置最低。综合分析认为,金属微粒畸变了其附近区域的局部电场,进而影响了材料表面的场致电子发射和SEEA过程,其对电场的畸变程度和畸变区域随微粒粒径和附着位置的不同而改变,因此导致材料的沿面闪络电压随微粒粒径增大而降低,同时因微粒附着位置不同而有所差异。

Metal particle has been considered to be an important reason leading to surface flashover along insulators. For the safe operation of electrical equipment, it is necessary to study the influence of metal particle on surface flashover characteristics of insulating material in vacuum. Consequently, we studied effects of metal particle on flashover characteristics and surface charging distribution under DC voltage. The results reveal that flashover voltage is significantly reduced when metal particle attaches on insulator surface; the larger the particle size is, the lower the flashover voltage will be, e.g., the withstanding voltage is reduced by 25% for a 2-mm metal particle. When changing the attached position of particles, e.g., near cathode, near anode and in the middle of cathode-anode surface, the flashover voltage is the highest for the first case and lowest for the last case aforementioned. Analyses reveal that metal particle distorts the electric field distribution, then affects the field emission and the secondary electron emission（SEE） process. And the distortion of electric field is associated with the particle size and attached position. So the flashover voltage decreases when increasing the particle size, and also changes with the particle attached position.