多次落雷条件下机构回弹对高压SF_6断路器开断特性的影响

Influence of Contact Bound on Interruption Characteristics of SF_6 Circuit Breaker Under Multiple Lightning

为了研究多次落雷导致断路器开断后断口处于分闸位置时发生热态二次击穿的原因,结合电弧磁流体动力学模型和SF_6-PTFE的临界击穿场强的计算数据,从弧后断口临界击穿电压的角度,重点分析了机构回弹对自能膨胀式断路器弧后电击穿特性的影响。结果表明:临界击穿电压在触头最大回弹位置附近下降至最低值448.6kV,小于二次落雷时断口间的电压507.5 kV,从而确定机构回弹是造成断路器开断后、雷击作用下发生二次击穿的主要原因。

To analyze the restrike phenomenon with the action of multiple lightning strikes on the high voltage AC transmission lines, considering the bounce of the movable contact, from the view of the critical dielectric breakdown voltage,we established a mathematical model to predict the post-arc dielectric breakdown by combining the magneto-hydro-dynamics（MHD） arc model and the calculated critical strength of dielectric breakdown of SF6-PTFE mixtures. It is indicated that the lowest value of the critical dielectric breakdown voltage is 448.6 kV, and appears at the maximum bounce position, which is less than the applied voltage to the contacts（507.5 kV）, so the bounce of the operation mechanism is the main reason for the restrike with the action of lightning.