Jan De Nul Wraps Up Cable Installation Job for TenneT’s DolWin Platform

(Credit: Jan De Nul)

Belgian offshore contractor Jan De Nul has concluded the 2025 transport and installation campaign of three HVAC grid connection cables at TenneT’s DolWin kappa platform.

When finalized, these cables will ensure the transport of almost 660 MW renewable electricity from two offshore wind farms, which is enough energy needed to power more than 800,000 German homes.

Jan De Nul and partner Hellenic Cables are responsible for design, production, transport, installation and protection of three 155 kV HVAC cables with a total length of 37 km. These cables provide a stable connection from the offshore wind farms Nordseecluster 1 and 2 to the offshore converter station DolWin kappa.

Cable-laying vessel Isaac Newton transported the three 155 kV cables from Hellenic Cables’ vertically integrated submarine cable plant in Corinth, Greece. The vessel installed them between the TenneT offshore converter station DolWin kappa and the two offshore wind farm locations of Nordseecluster 1 and 2. At crossings with other subsea infrastructures, the vessel installed concrete mattresses.

The multi-purpose vessel Adhémar de Saint-Venant buried the cables along the entire cable routes using her trencher UTV1200.

During the past two weeks, rock installation vessel Simon Stevin has installed about 25,000 tonnes of rock berms to ensure the protection of the HVAC interconnector cables on the seabed. These works conclude the campaign of 2025 at DolWin kappa.

In 2026, the last connection and testing works are planned, after the installation of the two offshore substations for the wind farms Nordseecluster 1 and 2.

TenneT’s HVDC DolWin6 project brings the renewable electricity of the two new offshore wind farms Nordseecluster 1 and 2 and the already existing offshore windfarm Gode Wind 3 in the German North Sea to the onshore grid.

These wind farms have a capacity of 900 MW and will produce enough renewable energy equal to the annual consumption of 1.1 million German households.

The works at DolWin kappa are one part of Jan De Nul’s long-term services to TenneT. In the future, several export cable projects are planned to connect 2G W converter stations to the onshore German grid.