With the successful testing of the Mitsubishi Electric HVDC line protection relay by EnergyVille/KU Leuven, significant steps have been taken towards the protection of future HVDC power systems. The tests have exposed the HVDC relay, a new technology to protect HVDC power systems of the future, to realistic inputs representative of those that it will experience in the future power system. Preliminary results show that the HVDC relay is able to perform the designed functions, as well as demonstrating reliable and secure operation, through large numbers of repetitive operations. The tests took place within the framework of the EU PROMOTioN project, in which effective HVDC protection systems for meshed offshore wind grids are developed and tested.

Towards Protection of High Voltage DC Networks

To enable the connection of large amounts of renewable energy, future power systems require a flexible bulk power transfer beyond existing capabilities. The most effective way to provide this additional capacity is through the use of High Voltage DC (HVDC) networks. Protection of such networks, however, requires novel equipment and algorithms to identify and clear faults from the system in a fast and selective way so that damage to equipment or extended loss of service are avoided. The HVDC relay is a piece of hardware that executes algorithms to detect and identify faults, and provides critical signals to other protection equipment.

Industrial HVDC relays are not yet commercially available and are presently under development. At EnergyVille and within the PROMOTioN project important steps have now been taken in the industrialisation of the dc relays. The specific relay tested uses protection algorithms designed by KU Leuven/EnergyVille and state-of-the-art hardware by Mitsubishi Electric. The relay has been tested using simplified, yet representative, test circuits, methods and procedures, in order to validate the reliable and timely operation of the algorithm running on industrial hardware. It has now been confirmed that the HVDC relay was able to provide the protection functions as expected following all tested fault and non-fault events, with an operation time significantly shorter than that of ac power system relays, and in-line with current expectations of future HVDC system requirements. Backup protection functionality, in the case of breaker failure, has also been successfully validated.

“Successful testing demonstrates that one key element of a future HVDC supergrid is industrialised and near ready for real-world application”, Dirk Van Hertem, professor at EnergyVille/KU Leuven explains.  “This sort of independent testing not only increases the confidence in protection algorithms and technology, but also aids discussion towards harmonisation – a key enabler for multi-vendor installations. We are proud that our ongoing collaborative work with Mitsubishi Electric has been able to build on our HVDC protection research to raise the technology readiness level of DC technology and to collaborate on an industrial solution that is ready to be used in a real system.”

“The testing performed by EnergyVille/KU Leuven represents another mile-stone in the development of our dc relay”, says Mr. Kenichi Kuroda, senior manager at Mitsubishi Electric Corporation Japan. “The hardware was able to perform as designed, detecting and discriminating faults within the tests system. The next steps are to evaluate the device at system level (tests performed at SHE transmission within Promotion WP9) and to move towards standardisation regarding substation protection equipment for future multi-terminal HVDC systems.

EnergyVille KU LeuvenMitsubishi Electric HVDC Line Protection Relay for Power Systems of the Future

PROMOTioN Project

The testing has been performed as part of the PROMOTioN project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 691714. The PROMOTioN project aims at increasing the confidence in future HVDC networks, by tackling technical, regulatory, financial and legal challenges to future European implementation. Demonstrating that novel HVDC protection methods are suitable for future power systems is a core part of the project, and real-time testing of protection strategies and HVDC relays are an important aspect within this.


W. Leterme, J. Beerten and D. Van Hertem, "Nonunit Protection of HVDC Grids With Inductive DC Cable Termination," in IEEE Transactions on Power Delivery, vol. 31, no. 2, pp. 820-828, April 2016.

W. Leterme, S. Pirooz Azad, and D. Van Hertem, ‘Fast Breaker Failure Backup Protection for HVDC Grids,’ in Proc. IPST 2015, Cavtat, Croatia, 2015.

G. Chaffey, I. Jahn, R. Loenders, W. Leterme, M. Wang, F. Dejene, S. Norrga and D. Van Hertem, ‘Functional Real Time Testing of HVDC IEDs,’ in Proc. CIGRÉ B4 Colloquium 2019, Johannesburg, South Africa, 2019.

Logo's Mitsubishi Relay Testings
profielfoto dirk van hertem


Dirk van Hertem

Professor Electrical Engineering at EnergyVille/KU Leuven, Research line coordinator electrical networks