Study on a Novel Energy-Dissipation Branch for 600 kV DC Circuit Breakers Based on Ga–In–Sn Liquid Metal

With the increase in voltage levels, higher requirements are imposed on the energy-dissipation capability of high-voltage direct current (HVDC) networks. Existing energy-dissipation schemes cannot satisfy the demands of future HVDC systems. In this paper, a composite energy-dissipation branch circuit based on liquid metal, zinc oxide varistors, and damping resistors is proposed for HVDC circuit breakers. First, the self-constricting arc initiation mechanism and energy-dissipation characteristics of gallium–indium–tin liquid metal are studied. The results show that the energy-dissipation process exhibits an obvious stage-wise characteristic. Subsequently, an energy-dissipation topology incorporating liquid metal elements is established. A simulation model for the liquid-metal module is developed using the Mayr arc theory, and the conductance evolution during arc initiation is simulated. The model is combined with a hybrid HVDC circuit breaker model for analysis. Finally, a composite energy-dissipation branch circuit is constructed. The energy allocation among different components and the corresponding power density are evaluated. In the case of connecting three liquid-metal components in series, the energy density reached 0.248 kJ/cm3, representing a 22.2% increase compared to the original. The results support the coordinated application of liquid-metal modules and conventional absorption units in HVDC circuit breakers.