Breakdown characteristics study of glycerol medium in coaxial pulse forming line
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摘要: 针对甘油介质在形成线中的应用,总结了甘油作为储能介质已开展的相关研究工作,并在缩比的同轴电极试件中进行了电极表面、磁场、耐压极性、含气量等条件对甘油介质击穿特性影响的实验研究。搭建了基于晶闸管控制的空心脉冲变压器升压实验平台,设计了浸没于脉冲磁场中的同轴电极击穿试件,实验平台最大输出电压500 kV,上升时间26 s,最大磁场1 T,可通过控制晶闸管的先后触发使击穿过程发生于准稳衡磁场中,并制作了外形一致、表面不同的砂纸打磨、羊毛抛光、金属电镀和非金属电镀四种电极。实验结果表明:甘油的击穿是没有极性的;1 T量级磁场对甘油介质的击穿特性无影响;不同电极表面微观形貌差异较大,使甘油介质具有不同的击穿特性,说明甘油击穿在电极表面的过程具有较大影响;充分的排气能减少甘油中直径较大的气泡,减少概率性的低击穿场强,击穿后产生的大量微小气泡会整体降低甘油的击穿阈值,使甘油的平均击穿场强降低。Abstract: As the glycerol medium has important applications in the pulse forming line, its breakdown characteristics are studied experimentally in a scaled coaxial specimen under different conditions, including electrode surface, magnetic field, bubbles and so on. A thyristor controlled air-core pulse transformer with a maximum output voltage of 500 kV and the rising time of 26 s is built. A coaxial breakdown specimen immersed in pulsed magnetic field with the maximum magnetic field of 1 T is designed. Through the control of thyristors, the breakdown can be limited in the quasi stationary magnetic field. Four coaxial electrodes with the same shape but different surface disposed measures including sanding, wool polishing, metal electroplating and nonmetal electroplating are manufactured. The experimental results show that the breakdown of the glycerol has no polarity; the magnetic field of 1 T has no effect on the breakdown characteristics of the glycerin; different electrodes have significantly different microcosmic morphologies, resulting in the differences between breakdown characteristics of the glycerol, indicating that some kind of electronical process on the electrode surface has much influence on the breakdown; the probability of breakdown in glycerol can be reduced by evacuating the bubbles with large diameters, and the generated tiny bubbles after the breakdown reduce the average breakdown strength of the glycerol.
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