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January 26, 2023

First Sea Cable Installed for TenneT's West Alpha Offshore Substation

©Flying Focus

©Flying Focus

Jan de Nul Group and LS Cable & System have completed the installation of the first sea cable for West Alpha offshore wind substation for Dutch grid operator TenneT. 

The offshore installation contractors used the cable-laying vessel Connector and the remote-controlled cable-laying vehicle UTV1200 for the operation.

Over sixty kilometers of cable were laid in the seabed between the Heemskerk beach on the Dutch coast and the  jacket foundation of the transformer platform at sea.

With over sixty kilometers of marine cable on board, the cable-laying vessel Connector from contractor Jan de Nul's fleet appeared off the coast of Heemskerk/Wijk aan Zee in mid-December. This cable section completed the first connection up to TenneT's Hollandse Kust 'socket' (West Alpha), Tennet said Wednesday.

Earlier last year, Jan de Nul pulled the two sea cables for 'west Alpha' from the Heemskerk beach into the jacket pipes under the dunes, and the first kilometres of cables were laid capped in the seabed. Some five kilometers from the beach, Jan de Nul pulled up the capped section of the first cable for 'west Alpha' in mid-December. On board the Connector, the end was then connected to the cable on board.

Following the connection by South Korean cable manufacturer LS Cable & Systems, the cable was placed back on the seabed. 

At the same time, Jan de Nul's work vessel Adhémar de Saint-Venant appeared offshore with the unmanned cable-laying vehicle the UTV1200 on board. As soon as the Connector set sail, the cable slowly unwound from the large turntable on board, followed a short distance away by the Adhémar to control the UTV1200, which then laid the cable into the seabed. TenneT said.

The jacket for TenneT's transformer platform was in August 2022 anchored to the seabed 50 kilometres off the coast of Egmond op Zee. 

Here, the first cable was successfully retracted through the cable deck in recent days. Next spring, Jan de Nul, using the cable-laying vessel Isaac Newton, will retrieve the remaining section for the second sea cable in South Korea so that this cable section can be installed.

In the summer of 2023, TenneT will have the ready-made superstructure (topside) installed on the jacket for (West Alpha), so that the grid operator can bring renewable wind energy ashore via this 'socket' from next year. With a capacity of 700 megawatts, the amount of renewable energy brought ashore corresponds to 2.5 to 3 per cent of current consumption in the Netherlands.

The February 2024 edition of Marine Technology Reporter is focused on Oceanographic topics and technologies.
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