电极熔蚀导致的气体开关绝缘子性能劣化

气体开关导通时,电极材料熔融或汽化并从电极表面移出,导致开关绝缘子被染污,并可能诱发开关内绝缘闪络事故,直接影响气体开关寿命和脉冲功率系统稳定性。在开关内嵌入有机玻璃圆环,收集黄铜电极熔蚀产物,并研究其对开关绝缘子表面形貌和沿面绝缘强度的影响。实验结果表明,电极熔蚀会产生大量金属蒸汽和溅射液滴,且熔蚀产物具有明显的轴向分布特性,其中,金属蒸汽冷凝并附着在绝缘子表面,形成细微的金属粉末;溅射液滴轰击绝缘子表面,在局部区域形成密集的表面裂纹和金属颗粒嵌入物。在两种电极熔蚀产物的共同作用下,开关绝缘子表面绝缘电阻下降,闪络场强降低;同时,绝缘子表面轴向不同区域的绝缘电阻差别很大,引起绝缘子表面电压分布不均和局部电场增强,最终导致开关绝缘子闪络电压降低,闪络概率增大。

Degradation of gas switch insulator due to electrode erosion

In the electrode erosion process, melted and evaporated metal removed from electrode surface may contaminate the gas switch insulator and increase the probability of flashover accident, influencing the lifetime of gas switch and the stability of pulsed power system. In this paper, researches on the degradation of morphology and insulating strength of insulator surface were carried out while PMMA and brass were employed as the insulator and electrode material respectively. The results show that the electrode erosion would generate plenty of metal vapors and ejected droplets. The metal vapors would congeal and produce tiny metal powder covering the insulator, meanwhile, the ejected droplets would bombard the insulator and generate dense cracks and embed metal particles. After 300 shots, the leak current of insulator surface increased and the flashover electric field decreased, on the other hand, the surface insulation resistance in different regions had a great distinction, resulting in an uneven distribution of electric field. As a result, the flashover voltage decreased and the probability of flashover accident increased.