Extruded HVDC cables will be a key technology in electrical power transmission.
High-voltage direct current (HVDC) underground and submarine cables constitute an essential technology for the long-distance transmission of electrical power with minimal losses, thereby enabling European decarbonization and reaching climate neutrality by 2050 in accordance with the European Green Deal. Increased physical interconnections via HVDC cable links across Europe will facilitate the grid-integration of renewable energy sources (RES) to provide clean energy, create a more competitive European transmission system, and reduce electricity prices for consumers and businesses.
Up to date, extruded HVDC cables have been used in projects typically up to 320 kV as well as in one 400 kV project totaling to 7,800 km installed length. ENTSO-E and EUROPACABLE estimate that in total Europe will need approximately 42,666 km HVDC land and submarine cables by 2030, accounting for 9,110 km and 20,728 km of on-shore and off-shore HVDC cables (≥320 kV) between 2022–2029, respectively.
Novel extruded HVDC insulation materials and manufacturing solutions optimize the cable performance.
Extruded HVDC cables with cross-linked polyethylene (XLPE), and more recently also thermoplastic polypropylene (PP)-based insulation, represent a new generation of HVDC cables, offering several benefits over conventional mass impregnated (MI) HV cables such as mechanical robustness, easier installation due to less complex jointing, lower weight and lower price, thus making them a very compelling new alternative.
Currently, extruded HVDC cable technology is considered well-established for 320 kV level. However, reaching TRL maturity for higher voltage levels up to ±600 kV is still a challenge, necessitating e.g. development of new HVDC insulation materials to overcome the issues related to space charge accumulation and accelerated ageing in state-of-the-art XLPE. In addition, new cable manufacturing solutions optimized specifically for thermoplastic HVDC cable extrusion should be developed, having the potential to provide significant cable performance and cost benefits in the future.
Expanding the utilization of extruded HVDC cable technology requires reliable operation and monitoring.
While extruded HVDC cables will be a key technology moving into the future, expanding their utilization to higher power transmission capacity and ensuring their reliable operation over the expected lifetime of up to 40 years still requires new technological developments.
The reliability of the HVDC cables and systems is crucial for the reliability and resilience of the whole transmission grid, to ensure satisfactory firewall properties against disturbances in the hybrid AC/DC network, and to foster the massive integration of remote renewables into the grid. Even though HVDC cable faults are very rare (average 0.2 trip/year), HVDC cable system failures can result in significant consequences in terms of costs and electricity supply. Thereby, new innovations in HVDC cable system condition monitoring and reliability modelling during operation lifetime are needed to foster proactive asset maintenance and prevent unplanned outages.
