TenneT engaged Jan De Nul Group for the repair of a cable fault located within the 500-meter zone around the DolWin alpha platform, 75 kilometers off the German coast north of the island Borkum. This offshore platform connects three wind farms in the German North Sea to the German extra-high voltage grid, and is therefore vital for these wind farms to get the green energy ashore.

Within less than 50 days, Jan De Nul performed the specific detailed engineering, the vessel mobilisation, the replacement of the damaged cable section, as well as the burial of the new cable and joint.

Benjamin Foubert, Operations Manager Offshore Cables at Jan De Nul Group: “We are very proud of this very well organized and swift repair. The extensive pre-engineering efforts we performed in view of this repair framework agreement clearly paid off. Achieving the full repair in such a short notice resulted in a minimal disruption of the offshore grid connection. Thanks to the close and pro-active cooperation between all parties involved we were able to complete this campaign successfully, which included our two vessels working simultaneously in close proximity of the offshore platform.”

Working simultaneously and close to the platform

For this repair job, Jan De Nul mobilised its Cable-Laying Vessel Isaac Newton and Multi-Purpose Vessel Adhémar de Saint-Venant. First, the Adhémar de Saint-Venant deburied the damaged cable section, including its cable protection system which was buried under large armour rock.

The Isaac Newton loaded the spare cable and repair joint in Emden, recovered the damaged cable section offshore and subsequently installed the new cable and joint with success. Jan De Nul’s jet-trenching vehicle PT1, installed on-board the Isaac Newton, completed the repair campaign by burying the new cable section 1.5 meters below the seabed.