A compact design for high voltage direct current circuit breaker

The absence of current-zero points in the direct current (dc) waveform of high voltage dc (HVDC) circuit breakers makes the interruption process more severe than the case of conventional ac networks with sinusoidal currents. In this way, in the current HVDC networks, a parallel precharged capacitor is inserted to inject the reverse current into the interruption chamber of the vacuum circuit breaker and create the artificial current-zero points. In this paper, a novel method for reverse current injection has been proposed. In this method, two separate helical flux compression generators (HFCGs) have been applied to generate the reverse current and an intense axial magnetic field (AMF), respectively. Numerical simulation of high-current vacuum arc (VA) in the presence of very strong AMF has been presented. For this purpose, the magnetohydrodynamic equations describing the behavior of the VA are coupled to a simple circuit analysis and the previously developed multiphysics model of HFCG. The results indicate that the explosively driven current injection set can make current-zero points properly in a typical HVDC network and lead to successful interruption of fault current. This method needs much less volume and cost in comparison to the parallel precharged capacitor sets. Index Terms--DC power transmission, pulse power systems, vacuum arc (VA), vacuum circuit breakers, vacuum interrupters (VIs).