石墨电极空气间隙的自击穿统计特性分析

在惯性约束聚变能源系统这类采用多支路并联结构的同步供电装置中,气体开关的放电分散性也即随机性可能带来严重的工作可靠性和稳定性难题。石墨电极具有较好的耐烧蚀能力,但石墨电极气体开关的自击穿概率必须控制在极低的范围才能使其满足严酷的工况要求。通过模拟工况的直流静态耐压实验,分析比较了各种石墨型材空气间隙的自击穿特性,结果表明平均粒径较小的纯石墨材料制作的空气间隙具有更狭窄的自击穿电压统计分布。彼得森(Pedersen)准则可以解释此现象,同时从数学上证明了自击穿故障发生的概率服从威布尔(Weibull)分布。合理地设计工作场强对静态耐压平均值的占比(即欠压比),可以较好地将单个气体开关及整个并联供电系统的误导通概率控制在设定值之下。所得结论对石墨型气体开关在大型并联脉冲供电装置中的研制和使用具有参考意义。

Self-breakdown Statistics Properties for Air Spark Gap of Graphite Electrodes

In a large pulsed power supply system with multiple branch parallel structure,the dispersing or randomness of the self-breakdown voltage could result in the serious problem of reliability and stability.Although the graphite electrodes have a good arc ablation-resistance,the pre-fire probability of spark gap switches with graphite electrodes must be controlled at extremely low levels to meet the rigorous requirement.Self-breakdown statistics of different graphite spark gaps in different air pressures were experimented in simulation work conditions.The experimental results revealed that the air gap made by the superfine pure graphite with small particle size had more narrow statistical distribution of self-breakdown voltages.This phenomenon can be explained by Pedersen rule.It is proved from the point of view of mathematics that the cumulative distribution of pre-fire probability obeys the Weibull model.Reasonable designing the under-voltage ratio of the graphite spark gaps can better control the pre-fire probability of multiple branch parallel structure caused by self-breakdown.