Modelling of the SF₆ circuit-breaker arc and of its interaction with the circuit

A physical model of an SF₆ circuit-breaker arc was developed to study the behaviour of the arc as zero current is reached and to analyse its interaction with the circuit. The role of turbulence, processed using the mixing length model adjusted with experimental results, is an essential factor in the extinction of the arc. The variations of post-arc current were calculated as a function of the rate of rise of recovery voltage (RRRV) and of the time lag before application of this transient voltage. The authors then linked their physical arc model to a circuit model. Calculation of the arc-circuit interaction showed that the disturbances brought about in the RRRV by the presence of the arc should be taken into account, since they modify the post-arc current and thus the interrupting capability of the circuit-breaker.