TenneT Germany
In mid-July, Jan de Nul completed works to connect the offshore windfarms Nordseecluster 1 and 2 to the DolWin kappa platform in the German North Sea for transmission system operator TenneT Germany.
As part of the project DolWin6, Jan de Nul transported, installed and protected three subsea HVAC cables connecting the wind farms to the DolWin kappa offshore converter station.
Together, these cables will transmit nearly 660 MW of renewable energy, enough to supply more than 800,000 German households with electricity.
In 2025, cable-laying vessel Isaac Newton transported and installed the three HVAC cables, spanning a total length of 37 kilometres to the German North Sea.
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.
Immediately after installation, the cables were buried beneath the seabed to protect them from external impacts. For this, Jan de Nul deployed trenching support vessel Symphony together with its trencher Swordfish. Using a jetting technique, which loosens the seabed with high-pressure water jets, the team safely buried the cables below the seabed.
In early July, our 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 1 and 2 substation platforms has been successfully delivered.
