The electrical substation:

Central element of the offshore wind farm

Installed since July 8, 2022, the electrical substation plays a key role in the operation of the offshore wind farm in the bay of Saint-Brieuc. Intended to transmit electrical flows between the wind turbines and the Earth, its installation is a particularly important step in the progress of the project.

Zoom on its characteristics.

Features and assembly

The electrical substation was designed and manufactured by the companies Iemants (a subsidiary of the Smulders group which, in turn, is a subsidiary of the Eiffage group) and Equans, with medium and high voltage equipment supplied by the company GE Grid solutions .
A complex and massive element, the electrical substation is made up of two elements manufactured separately and assembled at sea:

  • The lower part or “jacket” type foundation, which is fixed to the seabed by piles. 
  • The upper part or “topside”, which houses all the electrical equipment.

In terms of proportions, the power substation foundation is 63 meters high with a total weight of 1,630 tonnes. The upper part measures 55 meters long, 31 meters wide and 23 meters high, for a total weight of approximately 3,400 tonnes.

On the production side, the engineering and manufacturing of the jacket foundation and the metal structure of the upper part were carried out by the Equans-Iemants joint venture.

The low-voltage electrical part of the upper part was designed and equipped by the Equans company. It includes auxiliary systems and the integration of medium and high voltage equipment which are supplied by GE Grid Solutions.

The jacket and the upper part were pre-assembled by Smulders in Belgium, on the Hoboken site near Antwerp. Then, the final assembly of the upper part was carried out at the Equans shipyard, still in Hoboken, Belgium. Finally, the final assembly of the jacket foundation was carried out at the Heerema site in Vlissingen in the Netherlands.

Better understand how it works

The function of the electrical substation is to collect the energy produced by the park's 62 wind turbines, and to raise the voltage from 66 kV to 225 kV via power transformers. This collected energy is then injected into the terrestrial network, via a set of submarine cables, then underground. On Earth, it is carried out to the Doberie electrical substation, in the commune of Hénansal (22).

To ensure a reliable electrical connection between the park and the onshore grid, the electrical substation will house all of the park's automated control systems.

Connection to the electricity network 

The connection of the electrical substation to the onshore electricity network is planned for 2023. Commissioning of the electrical substation will be carried out by technicians from the Equans and Smulder companies. When operational, the fully automated electrical substation will be operated and controlled remotely. If necessary, technicians will be responsible for intervening for maintenance operations via personnel transport vessels.

The key stages of its installation

Loading and transport
On Saturday June 11, 2022, the upper part and the “jacket” foundation of the electrical substation were successfully loaded, in order to be transported to the offshore wind farm in the bay of Saint-Brieuc.

Initially, the loading of the upper part took place on the Equans BeLux , in Hoboken, Belgium.

At the same time, the jacket foundation of the electrical substation was safely loaded onto a pontoon from Vlissingen, in the Netherlands.


The installation of the electrical substation was carried out in two stages. First, the installation of the “jacket” foundation, weighing 1,630 tonnes, on its 4 piles. Then, the “topside”, weighing 3,400 tonnes, was installed on this foundation on the night of July 6, 2022. This two-stage maneuver was carried out by the Saipem teams and more precisely thanks to their ship -semi-submersible crane, the Saipem 7000. This vessel is one of the largest lifting boats in the world and uses technology particularly suited to this type of technical operation. This installation was finalized during the night of July 6 to 7, 2022.

This is the first electrical substation at sea in Brittany, but also the second substation installed in a French park after the one in Saint-Nazaire .

To follow the progress of the work and the next stages of installation of the elements of the park