SFCL‑based full-selective protection strategy for multi-terminal HVDC grids: A case study

A protection strategy for high voltage direct current grids using superconducting fault current limiters as main protection component is presented in this work. The proposed configuration ensures selectivity and allows continuous operation of the grid using low-speed mechanical DC circuit breakers for fault current interruption. A case scenario is presented in order to describe the primary and backup protection sequences using the aforementioned components. The comprehension of the electro-thermal behavior of the fault current limiter allowed us to find an optimal sizing of the different protection components. Off-line electro-magnetic transient simulation studies are presented to discuss the performances of the proposed strategy. Main findings were relaxation of technical specifications for DC breakers, continuity of converter station operation and the possibility of implementing simple protection algorithms to accomplish a selective protection.