On 2 February 2026, the HSI joint venture — comprising HSM Offshore Energy, Smulders (Eiffage group), and Iv-Offshore & Energy — completed the rollout of the OSS Zingst offshore substation topside for the OST-6-1 grid connection project. OSS Zingst is the second of two shared offshore substations being built for 50Hertz's Gennaker grid connection in the German Baltic Sea, following the earlier rollout of OSS Darß in October 2025. The topside was fabricated at consortium yards in the Netherlands and Belgium under the EPCI contract awarded by 50Hertz and Skyborn Renewables in December 2022. Both platforms will collect 220 kV AC power from Skyborn's 927 MW Gennaker offshore wind farm and route it via three submarine export cable systems to the Gnewitz onshore substation. With both topsides now completed and rolled out, the offshore transport and installation phase by Allseas can proceed, keeping the project on track for its mid-2028 commissioning target.
50Hertz reported that the OST-6-1 project (Gennaker) is "entering the home straight", indicating it has made important progress toward completion of its offshore grid connection works.
Upgrade to access detailed cable specifications, supply chain data, projected timeline, financial analysis, and more.
Grid connection OST-6-1 is the 50Hertz-operated HVAC export link that will transmit power from the Gennaker offshore wind farm in the German Baltic Sea to the onshore transmission network at Gnewitz. The system is designed as a 220 kV alternating‑current connection with a nominal transmission cap...
Owners
OST-6-1, Grid connection OST-6-1, Netzanbindung OST-6-1, Gennaker grid connection
State of Mecklenburg-Western Pomerania issued planning approval decision for the territorial waters section of OST-6-1, enabling offshore cable route work and onshore landing activities near Dierhagen.
50Hertz commenced construction at the Gnewitz substation site following approval under the Federal Immission Control Act (BImSchG). Construction well advanced by January 2026.
OSS Darss and OSS Zingst offshore converter platforms under construction by HSM Offshore Energy/Smulders/Iv consortium in the Netherlands. Allseas contracted for transport and installation.
In 2025, 50Hertz commenced offshore cable route work and onshore landing activities for the OST-6-1 grid connection near Dierhagen on the Baltic Sea coast. A 50Hertz press release dated 27 January 2026, announcing the cooperation agreement between 50Hertz and Skyborn Renewables for the Gennaker offshore converter platforms, states that a 2025 planning approval decision for the territorial waters section "enabl[ed] offshore cable route work and onshore landing activities near Dierhagen to begin last year." Since the press release is dated January 2026, "last year" refers to 2025, confirming that initial cable installation activities — including export cable route preparation and landfall works — commenced during 2025. The cable installation programme covers three 220 kV AC submarine export cable systems linking the offshore substations OSS Darß and OSS Zingst to the onshore substation at Gnewitz, with Hellenic Cables responsible for Lot 1 (western systems, ~105 km submarine + onshore) and ZTT for Lot 2 (eastern system, ~88 km total route). Asso.subsea is performing offshore cable laying for Lot 1 using its cable-laying vessel Atalanti.
Euroports Rostock, together with Hellenic Cables and Energieanlagen Ramonat, completed unloading the first batch of export cable drums for the OST-6-1 offshore grid connection project at the Euroports terminal in Rostock. The partners describe this as a major milestone for the 50Hertz-led grid connection, marking the start of heavy-cargo logistics to support installation of the cable system linking the planned Gennaker offshore wind farm in grid area O-6 to the German onshore transmission network.
On 3 October 2025, Smulders (Eiffage group), part of the HSI joint venture consortium with HSM Offshore Energy and Iv-Offshore & Energy, reported that OSS Darß, the first of two offshore substations for the OST-6-1 grid connection project serving the Gennaker offshore wind farm, had been completed and moved out of the fabrication yard. The platform was constructed at yards in the Netherlands and Belgium under the consortium's EPCI contract awarded by 50Hertz and Skyborn Renewables in December 2022. OSS Darß is one of two shared offshore substations (alongside OSS Zingst) that will collect 220 kV AC power from the Gennaker wind turbines and route it through three export cable systems to the onshore substation at Gnewitz. The rollout of OSS Darß from fabrication marks a key manufacturing milestone ahead of planned offshore transport and installation by Allseas, with commissioning of the full OST-6-1 grid connection system targeted for mid-2028.
Asso.subsea signed a contract with Hellenic Cables to perform offshore cable installation works for Lot 1 of 50Hertz’s OST‑6‑1 grid connection project serving the Gennaker offshore wind farm. Under this agreement, Asso.subsea will install two 220 kV AC submarine export cables from the Western Offshore Substation to the onshore joint bay along an approximately 40‑kilometre offshore route, using its cable‑laying vessel Atalanti and in‑house AssoTrencher V burial systems.
Cable route engineering completed. Hellenic Cables awarded turnkey export cable contract (105 km submarine + 13.5 km onshore, 220 kV).
According to 50Hertz’s tender for OST-6-1 cable route planning, the offshore route planning commissioned in the first quarter of 2023 is scheduled to be completed with the submission of the application for planning approval about one year later, implying a planned filing of the development consent application for the OST-6-1 offshore grid connection around the first quarter of 2024 with the competent authority in Mecklenburg-Western Pomerania.
On 25 August 2023, Zhongtian Technology Submarine Cable (ZTTSC) secured an EPCI contract from 50Hertz for Lot 2, the eastern part of the Gennaker OWF grid connection OST‑6‑1 in the German Baltic Sea. ZTTSC will supply and install a high‑voltage 220 kV export cable system between Offshore Substation East and the onshore substation near Gnewitz along an approximately 88‑kilometre route (about 55 km offshore and 33 km onshore), as well as a roughly 21‑kilometre high‑voltage bypass cable linking the western and eastern offshore substations, including all ancillary systems and accessories.
On 12 June 2023, the Ministry of Economic Affairs, Infrastructure, Tourism and Labour of Mecklenburg-Vorpommern held a scoping meeting for the OST-6-1 grid connection’s land route section, where 50Hertz presented the proposed scope of investigations for onshore cable laying and representatives of municipalities, authorities, environmental groups, administrations and companies provided comments to shape the environmental assessment requirements.
On 17 May 2023, 50Hertz submitted an application to initiate the scoping procedure for the land route section of the OST-6-1 grid connection, defining the scope of environmental and technical investigations required for onshore cable laying between the Gennaker offshore grid connection landfall and the new substation at Gnewitz.
In late February 2023, transmission system operator 50Hertz held a digital initial consultation (digitale Erstberatung) on the coastal water subsection of the OST-6-1 grid connection project. This public participation event focused specifically on the offshore cable route through German territorial waters (Küstengewässer) for the Gennaker grid connection, presenting the planned submarine cable corridor from the offshore substations to the landfall area near Dierhagen. The consultation was part of the formal early public participation process ahead of the planning approval procedure administered by the Ministry of Economics, Infrastructure, Tourism and Labour of Mecklenburg-Western Pomerania. This is distinct from the earlier late-2022 municipal consultations (which covered the broader project scope) and from the June 2023 scoping meeting (which addressed the onshore land route section). The coastal waters consultation represents a separate regulatory track for the subsea portion of the export cable route within the 12-nautical-mile zone.
By late 2022, 50Hertz had conducted early public participation for the Grid Connection OST-6-1 project, holding consultations with affected municipalities to present the planned Gennaker grid connection and collect their feedback ahead of the formal planning approval procedure at the Ministry of Economics, Infrastructure, Tourism and Labour of Mecklenburg-Western Pomerania.
In late December 2022, 50Hertz and wind farm operator Skyborn Renewables awarded a Dutch‑Belgian consortium of HSM Offshore Energy, Smulders, and Iv‑Offshore & Energy the contract to develop two offshore substations and associated jackets for the OST‑6‑1 grid connection of the 927 MW Gennaker offshore wind farm. The consortium will handle planning, engineering, component procurement, construction, offshore installation, and commissioning of the platforms and foundations, with fabrication to be carried out at yards in the Netherlands and Belgium.
On 22 August 2022, transmission system operator 50Hertz opened a tender for planning the subsea export cable route for the OST-6-1 grid connection that will link the 927 MW Gennaker offshore wind farm to the German grid. The contract covers engineering of an approximately 130‑kilometre offshore route and may include options for two additional cable systems (HPB2 and Spinnaker), with the tender open until 26 September 2022 and the contract period running from February 2023 to December 2025.
Showing historic events only. Subscribe for the full timeline including projected milestones.