弧触头烧蚀程度对灭弧室内短路开断过程多物理场的影响

为研究SF6断路器开断过程中弧触头烧蚀程度对灭弧室内多物理场变化的影响,建立了弧触头接触行程分别减小0、5、10和15Smm下灭弧室内开断过程的多物理场耦合仿真模型,获得了短路电流开断过程中灭弧室内温度、气流和电场分布特性。计算结果表明：开断过程中,弧道最高温度出现在弧根处,其值随弧触头烧蚀程度变化不大；随着弧触头烧蚀程度的加剧,SF6气体最高速度不断减小,吹弧效果减弱；最大场强集中在静弧触头端部或动弧触头弧角处,且随弧触头烧蚀程度加剧而畸变更严重。基于此,根据流注理论的气体击穿判据计算了不同弧触头烧蚀程度下SF6介质恢复特性,发现当弧触头接触行程减小15 mm时,临界击穿电压低于瞬态恢复电压,触头间隙可能再次击穿造成电弧重燃。研究结果可为SF6断路器电寿命退化机理提供理论支撑。

The Influence of Arc Contact Ablation Degree on Multi-Physical Field of Short-Circuit Breaking Process in Arc Extinguishing Chamber

In order to study the influence of the arc contact ablation degree on the multi-physical field changes in the arc extinguishing chamber during the breaking process of the SF6 circuit breaker, it is established multi physical field coupling simulation models of breaking process in arc extinguishing chamber that the arc contact stroke is reduced by 0, 5, 10 and 15 mm. The multi-physics coupling simulation model of the process obtains the temperature, airflow and electric field distribution characteristics in the arc extinguishing chamber during the short-circuit current interruption process. The calculation results show that: during the breaking process, the highest temperature of the arc appears at the arc root, and its value does not change much with the degree of ablation of the arc contact; with the increase of arc contact ablation, the maximum velocity of SF6 gas decreases and the arc blowing effect decreases; the maximum field strength is concentrated at the end of the static arc contact or the arc corner of the moving arc contact, and the distortion becomes serious with the ablation of the arc contact. Based on this, according to the gas breakdown criterion of the streamer theory, the recovery characteristics of the SF6 medium under different arc contact ablation levels are calculated, and it is found that when the arc contact stroke is reduced by 15 mm, the critical breakdown voltage is lower than the transient recovery voltage, the contact gap may break down again and cause the arc to reignite. The research results can provide theoretical support for the degradation mechanism of the electrical life of SF6 circuit breakers.