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Belgian offshore contractor Jan De Nul plans to install three subsea power cables and a fibre optic cable simultaneously on several upcoming offshore grid connection projects for TenneT, introducing what the company describes as the industry’s first such installation.
The work relates to the BalWin4, LanWin1, LanWin5 and BalWin5 grid connection projects in the German North Sea. Jan De Nul will begin the first of the four subsea cable projects this summer.
Across the four projects, around 2,000 kilometres of cable will be transported, installed and protected to connect future offshore wind farms to the onshore grid.
According to information published by Jan De Nul, the projects will see three power cables and a fibre optic cable installed simultaneously on the seabed, which has not been done before in the offshore cable installation sector. Part of the installation work will take place in the environmentally sensitive Wadden Sea, where shallow water depths and intertidal conditions require specialised installation methods and equipment.
To carry out the work in the Wadden Sea, the contractor built a dedicated cable-laying barge platform, named Waadrinner , consisting of three interconnected pontoons, each fitted with a cable carousel. The pontoons can operate together as a single installation platform, allowing the cables to be laid simultaneously over a section of around six kilometres while keeping equipment lightweight to minimise seabed pressure in the shallow environment.
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The company also upgraded its cable burial machine Sunfish to bury three power cables and a fibre optic cable at the same time. The system uses high-frequency vibrations to install the cables into the seabed, a technique described as less invasive than conventional cutting or high-pressure jetting methods.