IN Brief:
- Most of Windanker's 21 turbines are now exporting through the Ostwind 3 grid connection.
- The 300MW, 220kV connection runs through the Jasmund offshore platform, around 100km of subsea cable, and the Stilow substation.
- 50Hertz has a statutory completion date of 30 September, while Windanker's full commissioning is expected in Q4 2026.
50Hertz has completed final commissioning tests on the Ostwind 3 grid connection, allowing most of the 21 turbines at Iberdrola’s Windanker offshore wind farm to begin exporting electricity into Germany’s high-voltage transmission network.
The generating units are feeding power through the Jasmund offshore platform, the Ostwind 3 submarine and land cable system, and the new Stilow substation near Greifswald. The connection has a transmission capacity of 300MW and operates at 220kV between the offshore project and the onshore transformation point.
Ostwind 3 is the third 50Hertz offshore grid connection serving wind farm areas north-east of Rügen, following Ostwind 1 and Ostwind 2. Unlike those earlier projects, 50Hertz has responsibility not only for the cable system and onshore substation but also for the offshore substation.
The route starts at Windanker’s offshore collection point, about 42 kilometres north-east of Rügen. Approximately 100 kilometres of subsea cable carry the electricity towards the landing point near Vierow, followed by around 4.5 kilometres of underground onshore cable to Stilow.
At the onshore substation, voltage is transformed from 220kV to 380kV before the electricity enters the wider extra-high-voltage network. Stilow uses air-insulated switchgear, while its secondary systems provide the protection and control functions required to operate the connection from the 50Hertz control centre.
Export starts before full wind farm completion
The start of grid export is a different milestone from turbine erection. Offshore wind projects can have substantial generating equipment mechanically installed while their usable output remains dependent on cable circuits, substations, protection systems, telecommunications, and network commissioning.
Completion of the final connection tests demonstrates that the electrical chain is now operating across most of the Windanker array. That does not mean every element of the wind farm has completed commissioning, but it allows individual turbines that have passed their own tests to export through the completed grid infrastructure.
The wind farm is rated at 315MW and consists of 21 Siemens Gamesa SG 14-236 DD turbines. Each machine uses Power Boost to raise output to around 15MW, giving the project a generating nameplate slightly above the 300MW capacity of the Ostwind 3 grid connection.
That difference means the network interface, rather than the sum of turbine ratings, sets the maximum export capacity available through the connection. Wind farm controls have to manage output within that limit while also meeting voltage, reactive power, protection, and dispatch requirements at the grid boundary.
The Jasmund platform forms the offshore collection point for those power flows. It was built by the HSI joint venture comprising HSM Offshore Energy, Smulders, and Iv, and installed in the Baltic Sea earlier this year by Heerema Marine Contractors.
Its installation brought together structural fabrication, marine heavy lifting, high-voltage equipment, and offshore commissioning before cable and turbine interfaces could be energised. The platform now has to operate as part of a chain extending from individual turbines to the German 380kV network rather than as an isolated offshore asset.
Windanker is part of Iberdrola’s Baltic Hub alongside Wikinger and Baltic Eagle, giving the developer a German Baltic offshore portfolio of around 1.1GW. The concentration of projects creates operating efficiencies, but it also increases the importance of transmission capacity serving the same coastal region.
50Hertz is already progressing additional Baltic connections, including Ostwind 4 and the OST-6-1 system for the Gennaker wind farm. Cable corridors and onshore infrastructure are consequently being planned as a sequence of network projects rather than as one-off links attached to individual wind farms.
That approach is visible on the Ostwind 3 land route, where ducts for future connections have been installed alongside the current cable system. Combined civil works reduce the need to reopen the same corridor repeatedly as further offshore capacity connects.
The statutory completion date for Ostwind 3 is 30 September 2026. Windanker itself is expected to reach full commissioning during the fourth quarter, leaving the remaining turbine tests and project close-out to follow a grid connection that is already carrying power.
With export under way, the emphasis now shifts from construction progress to operational performance. The remaining programme has to bring all turbines through commissioning while maintaining reliable operation across Jasmund, the cable system, Stilow, and the 50Hertz network interface.
