Architectural limitations and comparison of ring and line-based DCSS topologies

This paper proposes the challenges associated with internal dynamics in the operation of Direct Current Switching Station (DCSS) designs involving fast acting Direct Current Circuit Breakers (DCCBs) of multiple topologies. Mitigation measures are proposed for the systems considered to allow multi-vendor systems and ensure safe operation throughout the interruption process. Analysis of ring and line DCSS systems has shown the current sharing dependencies of the ring DCSS can lead to ring-based current commutation local to the DCSS. Two design methodologies/approaches have been proposed for the ring commutation current limitation. The findings of this study are considered of importance in High Voltage Direct Current (HVDC) Multi-Terminal Direct Current (MTDC) grids with multiple protection zones.