Nexans completes deep-fjord 420 kV subsea cable project in Norway

Nexans and Statnett have successfully finalized the expansion of the 420 kV subsea power link across the Fensfjord in Western Norway. The project marks an important step in strengthening the regional transmission grid serving Bergen and nearby industrial areas.

The new subsea connection doubles electricity transmission capacity between Haugsvær and Lindås, reinforcing long-term power reliability in a region experiencing growing energy demand from both communities and industry.

Following cable installation in 2025, the project has now reached full contractual completion after energization and final certification.

Reinforcing a critical fjord crossing

Awarded in 2022, the project scope included engineering, manufacturing and installation of two high-voltage 420 kV HVAC subsea cables, each incorporating fiber-optic elements and bundled cables to support monitoring and communications.

Spanning approximately 7.8 kilometers across the Fensfjord, the route links the Mongstad area at Grunnevik to Iledalsvågen on the opposite shore.

World-record depth for HVAC subsea cable installation

One of the most demanding aspects of the project was the fjord’s extreme depth. The cable route reaches 530 metres below sea level — setting a world record for installation depth for this type of 420 kV HVAC subsea cable.

On the Mongstad side, the fjord descends sharply with slopes approaching 55 degrees before reaching deep water. To guarantee long-term stability, the cables were securely anchored along the slope, ensuring reliability over their expected 40-year operational lifetime.

Complex installation in deep and shallow waters

Installation activities required tailored engineering solutions to address both deep-water and shallow-water conditions.

At the Iledalsvågen landfall, shallow coastal waters meant the cables had to be floated for roughly 1.5 kilometers using buoyancy elements before being carefully lowered into position on the seabed. Prior to installation, the seabed along this section was stabilized with around 180 concrete mattresses and pipe mat, providing a secure foundation for the cable system.

Marine operations were carried out by the cable-laying vessel Nexans Skagerrak, supported by specialized workboats, shallow-water vessels and coordinated onshore installation teams.

With the project now fully commissioned, the Fensfjord crossing forms part of the broader effort to reinforce Norway’s high-voltage transmission infrastructure.

By increasing capacity across this key fjord link, the project helps ensure a stable electricity supply to homes, businesses and industry across the region, while also preparing the network to accommodate future demand and energy developments.

For Nexans, the successful completion of the project further demonstrates the company’s capability to deliver complex subsea cable installations in challenging environments — from steep fjord terrain to deep-water crossings.