A hybrid HVDC Breaker for 525 kV DC Switching Station Applications

This paper discusses the requirements to DCCBs and DCSS and presents a Hybrid HVDC

Breaker (HHB) platform designed to meet this purpose and seamlessly integrate into DCSS. The HHB circuit topology combines a low‑loss current path for normal operation and a parallel commutation path, which is essentially a power electronic breaker. The design is rated for voltages up to 550 kV, allows continuous currents up to 4 kA and interruption of fault currents up to 25 kA within less than 3 ms. The HHB uses semiconductor devices with a Short‑Circuit

Failure Mode, increasing robustness and redundancy. The absence of high voltage capacitors and the use of optical power supply to the gate units contribute to reduced safety risks and a maintenance schedule aligned to that of HVDC converter stations.

Besides its main breaking function, the HHB platform includes several features that support stable MTDC operation. One of these is proactive current limitation, which enables the breaker to limit the fault current levels before either initiating a final open sequence or resuming to normal operation. This helps protecting converters and limiting the impact of faults. The breaker also supports multiple auto‑reclosing attempts, which is important for overhead DC lines where temporary faults are more common. During these reclosing cycles, the breaker can keep the current flowing through the main breaker branch, which shortens the close-open sequence and reduces energy stress on components. Another useful function is soft‑start capability, which allows cables or converter stations to be energized with controlled current ramps. This avoids high inrush currents and can reduce the need for additional equipment.

The paper also describes how the HHB is integrated into a typical DC Switching Station layout for MTDC applications. The example station (NordWestHub in Germany as possible pilot project) includes several sectionalizing breakers, segregated control and protection zones, and clear paths for communication with both the station controller and the DC Grid Controller

(DCGC). These communication links ensure that the breakers operate in a coordinated way, support backup protection, and allow safe isolation of equipment during maintenance.

Test results and simulations presented in the paper show that the HHB can interrupt high fault currents, perform repeated reclosing cycles, and limit currents effectively during faults. Overall, the results demonstrate that the 550 kV Hybrid HVDC Breaker platform is technically mature and ready for application in future MTDC grids. Its combination of fast interruption, advanced operational functions, and robust design makes it a strong candidate for protecting large‑scale

HVDC networks and supporting their reliable and flexible operation.