Influence of contact bound on interruption characteristics of SF₆ circuit breaker under multiple lightning

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.