TenneT HKW Beta jacket foundation

Sleipnir Installs Hollandse Kust West Beta Substation Jacket

Heerema Marine Contractors’ crane vessel, Sleipnir, has installed the jacket foundation for TenneT’s Hollandse Kust (west Beta) offshore substation in the Netherlands.

On 16 May, the jacket foundation sailed on a floating pontoon from the Port of Vlissingen to its final destination about 53 kilometres off the coast of Egmond aan Zee.

The 49-metre-high structure was lifted from the floating pontoon by Heerema’s Sleipnir vessel last weekend and placed on the seabed.

The unit, weighing more than 2,100 tonnes, is firmly anchored at the four corner points using piles driven more than 50 metres into the seabed.

The Equans – Iemants (subsidiary of Smulders) joint venture signed the contract for the offshore transformer substation with TenneT in 2021.

At the beginning of May 2024, the jacket was loaded out of Smulders’ yard in Vlissingen. The substation topside is currently under construction at the Equans yard in Hoboken, Belgium, and will be installed next year.

From the beach at Velsen, contractor Boskalis/Orient Cable (NBOS) is currently installing sea cables that will connect the “socket” to the electricity grid in 2025.


The 220 kV cables are laid at a safe depth and connected to the land cables behind the dunes, said TenneT. Through this connection, the electricity from the 700 MW project will be fed to the high-voltage grid via the transformer station in Wijk aan Zee.

TenneT’s “socket” is intended for the wind farm that RWE/OranjeWind will build at sea in the coming years.


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