Study on the influence of mechanism dispersion on transient recovery voltage distribution of modular DC vacuum circuit breakers

A simulation analysis and an experiment are carried out to investigate how the gap difference between the breaks of a direct current vacuum circuit breakers with multi-breaks (MB-DC VCB) caused by the mechanism dispersion of the breaker influences the distribution of TRV among the breaks. An interruption model of MB-DC VCB, combining the continuous transition model, is established to analyse the rising rate of transient recovery voltage and the dielectric strength recovery speed of the breaks for MB-DC VCB under different gap difference conditions. Based on the experimental platform of dual break DC vacuum circuit breaker breaking, the correctness of the simulation model is verified on a DC VCB with the double-breaks interruption experimental platform. Moreover, a model is applied to the non-synchronous interruption simulation of a DC VCB with three-breaks. The relationship between the TRVs of the breaks under different gap difference conditions is analysed using the comparative analysis method, obtaining the maximum gap difference at the moment of breaking failure. The results of this study show that large-gap breaks have a higher TRV than small-gap breaks (the fracture of the action delay module), with double fractures reaching 1.4 times and triple fractures reaching a maximum of 1.52 times; the ability of small-gap breaks to withstand TRV is weak, giving rise to re-breakdown or even interruption failure; as the number of fractures increases, the maximum gap difference also increases. Improving the synchronous interruption ability of the MB-DC VCB is conducive to improving the interruption performance and interruption success rate of this type of a circuit breaker.