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NKT has completed planned cable replacement work on the Dutch section of the NorNed interconnector, restoring the 580 km, 450 kV link between Norway and the Netherlands. The interconnector, jointly owned by TenneT and Statnett, enables the exchange of up to 700 MW of renewable hydropower and wind energy between the two countries. The outage began in April and concluded in early June 2025, with minimal disruption. NKT delivered new onshore high-voltage cable systems in Eemshaven and refurbished existing terminations. Parts of the new 450 kV cable supply will be retained as spares. The project forms part of an ongoing service level agreement between NKT and TenneT (ReNews)
Why does this matter? Public discourse around the energy transition often emphasises the expansion of renewable infrastructure – such as the number of new wind farms or the minerals required for the continued expansion of green technologies. However, the NorNed cable replacement serves as a reminder that maintaining existing green energy systems is equally critical. This is not the first time or the last time that the NorNed cable will need to be repaired.
The underwater cable is made of a single core HVDC cable and a double-core Flat Mass-Impregnated (FMI) cable, both of which use copper as the main conductive component. When built, the project used approximately 9,000 mt of copper and 12,000 mt of lead to create the cable. These volumes underline the essential role of continued resource extraction by mining companies, such as Rio Tinto, in sustaining both the development and the maintenance of green energy infrastructure.
While subsea cables such as NorNed are central to Europe's renewable energy security, they also represent potential vulnerabilities. In late 2023, the Estlink cable between Finland and Estonia was severely damaged when the vessel Eagle S dragged its anchor across the seabed for 62 miles, an act some have interpreted as politically motivated interference from Russia. Statnett, Norway’s transmission system operator, has since raised concerns over the security of sea cable infrastructure, especially amid growing geopolitical tensions.
While the European Subsea Cable Association attributes most cable damage to fishing or anchoring activities, it emphasises the importance of energy supply diversification to mitigate potential disruptions. This underscores the need not only for increased green energy infrastructure but also for a sufficient stockpile of materials and properly maintained equipment for rapid repairs and expanding network resilience.
Environmental concerns over subsea cable installation have been addressed by studies showing negligible impact on marine ecosystems. In the UK, bodies such as Natural England and the Joint Nature Conservation Committee have approved cable projects in designated marine conservation zones, supporting their continued deployment under strict environmental regulations. This promotes the technology, with minimal environmental impact accompanying an estimated reduction of 1.7 million mt of CO2 per year between Norway and the Netherlands.
Most subsea cables are engineered for a 25-year operational lifespan, though newer technologies are gradually extending this timeframe. However, the need for ongoing access to metals and minerals remains a strategic priority. As renewable energy networks expand, ensuring secure and a green transition, sustainable supply chains for essential materials will be vital for both system expansion and maintenance.