Performance of a superconducting breaker for the protection of HVDC grids

Future multi-terminal high-voltage direct current (HVDC) grids will be essential for the electric power system expansion. However, there are still several technical, economic and legal obstacles that interfere with the construction of those grids. One of the main technical issues is the interruption of DC currents when a fault occurs, due to the high values of DC fault currents that can exceed the DC circuit breakers (DCCB) interruption capability in few milliseconds. In order to overcome that limitation, a superconducting DCCB (S-DCCB) is presented in this study. The proposed S-DCCB is based on the combination of a superconducting fault current limiter, a mechanical DC circuit breaker and a current limiter reactor. The presented S-DCCB is modelled and simulated by PSCAD/EMTDC software on a four-terminal HVDC system. Its behaviour is proven to be satisfactory for several fault scenarios. DC fault currents are initially limited and afterwards interrupted by the S-DCCB in an operation time that fulfils DC grids' protection requirements.