Successful installation of three HVAC export cables in German waters

Jan De Nul Group successfully completed the export cable installation works in the German North Sea in order to connect the offshore wind farms Trianel Windpark Borkum II, developed by Trianel, and Borkum Riffgrund II, developed by Ørsted, to Tennet’s German transmission grid.

For both cable installation projects, Jan De Nul Group’s cable laying vessel Willem de Vlamingh and trenching support vessel Adhémar de Saint-Venant were mobilised. “The successful completion of both projects will add onto our extensive track record for the installation of submarine power and umbilical cables for both the renewable and the oil & gas energy sectors,” says Wouter Vermeersch, Manager Offshore Cables at Jan De Nul Group.

Connecting offshore wind farms to the main land

In the summer of 2017, Willem de Vlamingh identified and removed potential UXOs from the cable routes. In the spring of 2018, she sailed to the cable load out facilities in Greece to load the three cables with a total length of 26.4 km. Willem de Vlamingh successfully completed the installation of all three cables on 25 April 2018.

The first two cables connect the Borkum Riffgrund II wind farm substation with the Dolwin Gamma convertor station. The third cable connects the Trianel Windpark Borkum II with the Dolwin Alpha convertor station. These Dolwin platforms convert the electricity generated by the two wind farms into Direct Current (DC) before transporting it to Tennet’s onshore network.

The trenching support vessel Adhémar de Saint-Venant executed the cable protection works by means of post-lay jet trenching using Jan De Nul Group’s UTV1200 trencher. Trenching was completed on 16 May 2018.

Final commissioning

The Greek cable manufacturer Hellenic Cable is currently terminating and testing the cable connections. Overall commissioning is planned in June/July 2018