Nexans deploys world's longest and deepest 420 kV XLPE cable system

Nexans has been engaged to deploy the world’s longest and deepest 420 kV XLPE cable system. The €78 million project is part of a new power link crossing two of Norway’s fjords.

BKK Nett AS, one of Norway’s largest utility companies, is building the new connection to reinforce the power grid in the west of the country. The new power line is essential to ensure security of supply for the forecast growth in consumption by residents, businesses and industrial consumers in the Bergen region, which is an important growth area. It will also provide additional capacity for the grid connection of new-generation resources.

The total length of the new 420 kV Mongstad to Kollsnes connection will be around 30 km. On land, overhead lines will carry the power. However, the majority of the route crosses two fjords, requiring the installation of submarine cables.

Nexans is providing a comprehensive turnkey service for the design, manufacture, supply and installation of a total of 90 km of single-core XLPE cable. The design is based on the same technology used in Statnett’s successful Ormen Lange project, commissioned in 2006, then the world’s first 420 kV XLPE submarine cable installation.

The submarine cables will be installed in the fjords in three parallel lengths to create a three-phase AC connection, rated at 420 kV. The cables will be protected by outer shells or water jetting from shore to 30 m water depth. The Lurefjorden installation will have a length of 10 km per phase and a maximum water depth of 200 m, while the Hjeltefjorden section will set a new world record for 420 kV XLPE cable covering both length (20 km per phase) and depth (a maximum 390 m).

“This major project for BKK reinforces Nexans’ position in Norway as a key supplier of cable infrastructure projects with over 100 years of experience on the country’s coast, islands and fjords,” said Kjetil Hovland, vice president submarine high voltage at Nexans.

“It also confirms Nexans as a world leader in 420 kV XLPE submarine cables with proven capability to deliver complete turnkey systems.”

The submarine cable will be manufactured at Nexans’ specialised facility in Halden, Norway, for delivery and installation between 2016 and 2017.