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Baltic Eagle's substation topside gets lifted into place

4C Offshore | Tom Russell
By: Tom Russell 23/02/2023 50 Hertz

The Offshore Substation Topside (OSS) for the
Baltic Eagle offshore wind farm has been installed off the island of Rügen, in the German waters of the Baltic Sea. The topside lifting operation was executed by Heerema Marine Contractors using the Thialf installation vessel.  

The substation consists of a foundation and a topside housing the transformers as well as electrical equipment. Its four-legged steel jacket foundation weighs approximately 2,900 tonnes and is fastened with two hammered piles at each leg. The topside features a closed multi-storey module of five decks. The jacket foundation was installed at the site back in October 2022.

The role of the OSS is to collect the electricity generated by the wind turbines and transform the supply voltage before feeding it into the onshore power grid at the Lubmin grid interconnection point. The installation involved the heaviest lifting operation for the Baltic Eagle project with a total estimated net weight of more than 4,200 tonnes.

Once the wind farm is connected to the grid, the electricity generated by its wind turbines will be delivered via inter-array cables to the offshore substation where it is then transformed from 66 kV to 220 kV and transmitted via two high voltage subsea cables across the 90 km distance to the landing point at Lubmin into the 50Hertz transmission grid. The 220 kV submarine cables were previously installed in 2021 and 2022 and deposited on the seabed at a safe distance from the platform position. The next step will be to move the two cable ends into the transformer platform in the second quarter of this year.

In May 2021, Iberdrola and German transmission system operator 50Hertz signed an agreement to cooperate on the construction, installation and commissioning of the OSS for Baltic Eagle offshore wind farm. Iemants-Fabricom was responsible for the manufacturing of all structural elements of the substation, the marine contractor Heerema for transportation and installation, and Siemens Gas and Power for the delivery of all main electrical equipment for Iberdrola's low-voltage part of the OSS. 

Iris Stempfle, Managing Director of the Offshore Division and Deputy CEO of Iberdrola Deutschland, said: "The offshore substation is a key piece of technology for supplying sustainable energy to hundreds of thousands of households and for the decarbonisation of German industry. We are very pleased to have achieved this central milestone in close cooperation with 50Hertz as planned."

Stefan Kapferer, CEO of 50Hertz: "The Baltic Sea still has a lot of potential and 50Hertz, together with partners such as Iberdrola, will help to achieve the German and European offshore targets: I congratulate everyone involved on the successful installation of the substation Baltic Eagle. Now we are once again a big step closer completing the Ostwind 2 grid connection project until next year."

Baltic Eagle's developer Iberdrola is now preparing the OSS for energisation. This will be followed by the installation of the monopile foundations, transition pieces and then wind turbines. The monopiles have been manufactured by the regional company EEW SPC from Rostock.

The 476 MW Baltic Eagle project will span a 40 km2 area and is expected to be completed in 2024 and consist of 50 Vestas V174-9.5MW wind turbines mounted on monopile foundations. It is Iberdrola's second array to be built in the Baltic Sea, following Wikinger. The two wind farms, together with the 300 MW Windanker project, form the company's "Baltic Hub" in the Baltic Sea.
The offshore grid connection for Baltic Eagle forms part of the wider Ostwind 2 project which will also connect the Arcadis Ost 1 offshore wind to the German high voltage grid. To transfer the power from the two wind farms, 50Hertz is building three submarine cable systems that will transmit a total of 750 MW.


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