Analysis of DC circuit breaker performance in multi-terminal HVDC grids considering fault dynamics and reclosing behaviour

This paper investigates transient fault behaviour on overhead lines (OHLs) within multiterminal high-voltage direct-current (MTDC) systems, with emphasis on the energy-absorption requirements of DC circuit breakers (DC-CBs) during fault interruption and reclosing. OHLs differ electrically from cables: they exhibit higher characteristic impedance and faster electromagnetic wave propagation, which produce distinct fault transient signatures. OHLs are also more prone to transient faults unlike cable systems. These characteristics motivate the need for reclosing-capable DC-CBs in OHL-equipped MTDC systems; a typical strategy is to attempt a reclose a few hundred milliseconds after interruption, so that in case of a transient fault, the system can keep operating nominally. When interrupting…