The contact ablation and deterioration of circuit breaker after capacitor bank switching can change the pre-breakdown time of closing operation

which will not only affect the effect of phase selection closing

but also indicate that the duration of pre-breakdown arc can be used as one of the indicators to measure the ablation status of the contacts. An electric-fluid coupling simulation model is set up for the pre-breakdown process of interrupter of 126 kV SF

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circuit breaker

and the pre-breakdown characteristics of the contact in the process of contact deterioration are studied. Moreover

the live detection method of the pre-breakdown time is proposed. The results show that the maximum point of the electric field strength always appears on the surface of the stationary arc contact during the closing process. The density of SF

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gas in the interrupter remains almost unchanged. At 110 kV phase voltage

the test value of the pre-breakdown duration of the contact with the variation of ablation degree is in agreement with the simulation value. From the perspective of electric field distortion

the variation of the pre-breakdown duration corresponding to the increase of the surface ablation deterioration of the contacts is explained. The results can provide theoretical guidance for the phase selection and closing strategy of the circuit breaker as well as the state evaluation of the contacts.