Offshore Installation OSS Jasmund

Grid Connection Platform for Windanker Offshore Wind Farm Installed in Baltic Sea

Offshore Platforms

HSI, a joint venture between HSM Offshore Energy, Smulders and Iv, has installed the Jasmund offshore substation (OSS), which will connect the Windanker offshore wind farm to the German electricity grid, at its designated location in the Baltic Sea.

Offshore Installation OSS Jasmund
HSI Joint Venture

The Jasmund platform is part of the Ostwind 3 grid connection project, which will collect 300 MW from the Windanker wind farm from October and transmit it to the German grid on land, according to 50Hertz, for which this is the first offshore platform in the Baltic Sea for whose construction and operation the company is the responsible transmission system operator (TSO).

The Jasmund OSS jacket foundation was manufactured by Smulders in Vlissingen, the Netherlands, and sent to the Baltic Sea at the beginning of December 2025, with the topside, manufactured at the HSM Offshore Energy Stormpolder yard near Rotterdam, shipped a few days after the jacket.

The installation was carried out by Heerema Marine Contractors at the project site, located northeast of the island of Rügen, where the platform was lifted onto the foundation on 17 December 2025, according to 50Hertz.

In the coming period, offshore testing and commissioning activities will be carried out to prepare the Jasmund OSS for operation, according to HSI Joint Venture, which is delivering the project under a contract covering the full EPCIC scope (engineering, procurement, construction, installation and commissioning).

The expected completion date for the Ostwind 3 grid connection system and the Windanker offshore wind farm, which is being built and operated by Iberdrola, is 30 September 2026, 50 Hertz says.

The Jasmund OSS is the first of three offshore substations being delivered by HSI Joint Venture for 50Hertz. OSS Zingst and OSS Darß will follow as part of the OST-6-1 grid connection, with OSS Zingst connecting the Gennaker East offshore wind farm and OSS Darß connecting the Gennaker West offshore wind farm to the onshore transmission network.

“After Ostwind 1 and 2, Ostwind 3 is the next project in the sea area northeast of Rügen, which we will complete on time and within budget”, said Stefan Kapferer, Chairman of the Management Board of 50Hertz.

“We are also on track with the next OST-6-1 project with a transmission capacity of 927 MW, which serves to connect the Gennaker wind farm north of the Fischland-Darß-Zingst peninsula. Two offshore platforms are already under construction, the laying of protective pipes has begun, and a new substation near Gnewitz is taking shape.”

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