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Jan De Nul successfully connects TenneT’s electricity network in The Netherlands and continues to invest in its offshore installation fleet in support of its energy business

Posted on November 28, 2022

On 17 November 2022, Jan De Nul Group completed the first part of the cable installation works to connect the wind farms Hollandse Kust (noord) and (west Alpha) to the Dutch mainland. Also the 220-kV high-voltage tests of both sea and land cables for Hollandse Kust (noord) were successfully completed, from the onshore substation to the substation located 18 km offshore.

Also on 24 November, Jan De Nul signed a contract with Global Marine Systems Ltd. for the acquisition of the Offshore Support Vessel Global Symphony. This marks a further investment in the offshore installation capacities of the Luxembourg-based maritime contractor.

Wouter Vermeersch, Manager Offshore Cables at Jan De Nul Group:“The Hollandse Kust (noord) and (west Alpha) project showcases our expertise in cable installation works. Jan De Nul has a very modern cable installation fleet, with three large cable installation vessels, supporting trenchers and amphibious cranes. Our investment in an additional Offshore Support Vessel, that in legacy of her history and track record will be renamed as Symphony, underlines Jan De Nul Group’s vision to offer the world a solution to the badly needed energy transition. With the success in the Netherlands and the investment in its offshore installation fleet, Jan De Nul validates its expertise in and resolute commitment to this energy transition.”


The cable installation vessel Isaac Newton installed the cables on the seabed. In addition, Jan De Nul used several remote-controlled underwater trenchers and amphibious cranes in the surf zone to bury and protect the cable in the seabed. The Moonfish (picture) is one of these trenchers, a Jan De Nul design tailored to the needs of this project.

In the spring, the cable installation vessel Isaac Newton collected the first lot of 90 kilometres of sea cable from our consortium partner LS Cable & System in South Korea. After arriving in the Netherlands, the Isaac Newton installed four different sea cables, starting from the beach.

  • Two cables were laid in one length on the seabed, all the way to the transformer station of Hollandse Kust (noord).
  • For the connection to the transformer station of Hollandse Kust (west Alpha), the Isaac Newton installed the first 8 kilometres of both sea cables, starting from the beach.

Next, the trencher Moonfish set to work, burying and protecting the sea cables in the seabed.

  • In the first phase, the Moonfish buried the first section of the two Hollandse Kust (noord) sea cables in the seabed, from the beach up to 3 kilometres offshore, at a depth of about 6 to 8 metres. From three kilometres offshore, the submarine vehicle UTV1200 took over, laying the cable up to the transformer station. This ‘offshore socket’ is located 18 kilometres off the Dutch coast.
  • After the summer high season, in October, Jan De Nul completed this first installation campaign by burying the two cable sections for Hollandse Kust (west Alpha) from the beach up to 3 kilometres offshore.

Caption picture below: The cables marked in green have been successfully installed, buried and tested. The cables marked in black will be installed in the spring of 2023. The red line indicates the 3 km boundary to where the Moonfish has buried the cable sections.


The Moonfish on wide tracks has been designed and made to lay cables underwater, up to 35 metres deep. With its long metal sword and powerful water jets, the Moonfish buries the cables in the seabed.

A floating water pipe pumps water to the powerful water jets on the Moonfish’s long metal sword. With this, the Moonfish makes a deep trench in the seabed, where it simultaneously lays the cable at a depth of up to 8 metres. The trench is then immediately backfilled. As a result, the cables are safely protected against future coastal erosion.

Ward Mertens, Project Manager for Jan De Nul Group: “Preparations started this year on the 1st March, immediately after the storm season. Our daughter company Soetaert installed four long cofferdams for the sea cable’s reception pits. Simultaneously, we dredged away the sand dunes just off the coast to clear the path for the Moonfish. The Moonfish set to work at the end of May. Controlled from the jack-up installation vessel just off the coast, the machine drove up to the beach. With the onset of a beautiful sunset, the machine got moving for the first time and buried the first sea cable at a depth of 8 metres. A fantastic moment after almost 2 years of engineering!”


In total, Jan De Nul is installing four sea cables in three installation campaigns. These sea cables will connect the transformer stations of the two wind farms Hollandse Kust (noord) and (west Alpha) to the mainland. Each transformer station will receive two cables, all together accounting for a total cable length of 235 kilometres.

Jan De Nul still needs to install two more cable sections to connect the future wind farm Hollandse Kust (West Alpha) to the grid. Jan De Nul’s cable installation vessel Connector will collect the first in South Korea, transport it to the Netherlands and then install it. The Isaac Newton will again be deployed for transporting and installing the final sea cable section.

With the success in the Netherlands and the investment in its offshore installation fleet, Jan De Nul validates its expertise in and resolute commitment to this energy transition.

Wouter Vermeersch

Manager Offshore Cables at Jan De Nul Group


Built in 2011, the Symphony has an extensive 1,400 m² deck space and is amongst others equipped with two 150 HP work class ROV systems and a 150 tons AHC crane. Thanks to the design of the vessel, the Symphony can operate in higher seastates.

The Symphony will predominantly be used to support our cable installation activities and will operate as a dedicated Trenching Support Vessel. Our recently delivered state-of-the-art newbuilt trencher Swordfish will be installed on board of the Symphony by the first quarter of 2023.

Thanks to this and other investments throughout the past years, Jan De Nul Group operates today a very modern and balanced offshore fleet, comprising this offshore support vessel, two offshore jack-up installation vessels, three floating crane installation vessels, three cable-lay vessels, five rock installation vessels and two multipurpose vessels.

Jan De Nul Group shapes water and land. Through a creative and innovative approach, we achieve sustainable and successful results. With us, the client can rest assured. Today, but also tomorrow.




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