Jan De Nul has completed the works necessary to connect the offshore wind farms Nordseecluster I and II to the DolWin Kappa platform in the German North Sea for transmission system operator Tennet Germany.
As part of the DolWin6 project, Jan De Nul transported, installed and protected three subsea HVAC cables connecting the wind farms to the DolWin Kappa offshore converter station.
The company said that together, these cables will transmit nearly 660 MW of renewable energy, enough to supply more than 800,000 German households with electricity.
In 2025, Jan De Nul's cable laying vessel Isaac Newton transported the three HVAC cables, spanning a total length of 37 kilometres, from Hellenic Cables' manufacturing facility in Corinth to the German North Sea.
Once on site, the vessel installed the cables on the seabed, successfully completing the first installation campaign by the end of the year.
In May this year, Isaac Newton returned to the project site to recover the three cable ends from the seabed and connect them to the Nordseecluster 1 and 2 platforms. Four Jan De Nul teams supported these operations around the clock from the offshore platforms.
Immediately after installation, the cables were buried beneath the seabed to protect them from external impacts. For this, Jan De Nul deployed the trenching support vessel Symphony together with its trencher Swordfish.
Using a jetting technique that loosens the seabed with high-pressure water jets, the team safely buried the cables below the seabed.
In early July, the rock installation vessel Simon Stevin departed Norway carrying 2,000 tonnes of rock. The material was placed around the three cable connections at the platform foundations, where additional protection was required. During the first campaign in 2025, the vessel had already installed another 25,000 tonnes of rock along the cable route.
With these final activities completed, the HVAC cable project between the DolWin Kappa converter platform and the Nordseecluster I and II substation platforms has been successfully delivered.
