Jan De Nul has completed the 2025 transport and installation campaign for three high voltage alternating current grid connection cables at TenneT’s DolWin kappa offshore converter station in the German North Sea. Once fully commissioned, the cables will enable the transmission of almost 660 MW of renewable electricity from offshore wind farms to the grid.
Jan De Nul, together with partner Hellenic Cables, is responsible for the design, manufacture, transport, installation and protection of three 155 kilovolt high voltage alternating current cables with a combined length of 37 kilometres. The cables connect the offshore wind farms Nordseecluster 1 and Nordseecluster 2 to the DolWin kappa converter platform.
The cable laying vessel Isaac Newton transported the cables from Hellenic Cables’ submarine cable manufacturing facility in Corinth, Greece, and installed them between the offshore wind farms and the converter station. Concrete mattresses were placed at crossings with existing subsea infrastructure.
Cable burial along the full route was carried out by the vessel Adhémar de Saint-Venant using the UTV1200 trencher. In the final phase of the campaign, the rock installation vessel Simon Stevin installed around 25,000 tonnes of rock berms to protect the cables on the seabed, bringing the 2025 works at DolWin kappa to a close.
Final connection and testing activities are scheduled for 2026, following the installation of the two offshore substations serving Nordseecluster 1 and 2.
The DolWin kappa connection forms part of TenneT’s wider offshore grid programme, which also includes the DolWin6 high voltage direct current project linking Nordseecluster 1, Nordseecluster 2 and the existing Gode Wind 3 offshore wind farm to the onshore grid. Together, these wind farms have a combined capacity of 900 MW. Further export cable projects are planned to connect future 2 GW converter stations to the German grid.
