ABL appointed to provide marine warranty survey for 2 GW Ostwind 4 grid connection

50Hertz has appointed energy and marine consultancy ABL to provide independent marine warranty survey (MWS) services for the Ostwind 4 offshore grid connection in the German Baltic Sea. The MWS scope covers transportation and installation of subsea cables and offshore infrastructure, and the installation of an offshore converter platform and associated assets.

Ostwind 4 is a 2 GW grid connection that includes an offshore converter platform, an onshore converter station and a roughly 110-kilometre direct current (DC) cable system. The project will use high-voltage direct current (HVDC) technology and represents the first deployment of a 525 kV HVDC transmission system in the German Baltic Sea.

Existing contracts and project partners

50Hertz previously awarded the contract to build and install the converter stations to Drydocks World and GE Vernova in 2024. NKT was awarded the onshore connections and offshore cable systems contract in September 2023. Ostwind 4 will connect the 1 GW OstSee Energies offshore wind farm, developed by TotalEnergies, to the mainland. The connection sits about 30 kilometres northeast of Rügen Island and links the O-2.2 site between the Arcadis Ost 1 and Baltic Eagle wind farms.

• Review and approve technical documentation and procedures related to marine operations.
• Assess the suitability of the proposed marine spread and provide marine risk and assurance services.
• Provide on-site attendance to witness and approve all warranted operations during transportation and installation.

The appointment follows ABL's recent contract to provide marine warranty survey and marine assurance services for the 976.5 MW Gennaker offshore wind farm in the German Baltic Sea, where its scope covered marine transportation and installation of foundations and other offshore infrastructure.

Marine warranty surveyors provide independent assurance that marine operations are planned and executed in ways that meet project-specific and insurer-required standards. For Ostwind 4, that assurance spans long cable routes, heavyweight offshore lifts and the first 525 kV HVDC installation in the region — factors that raise the technical and marine-risk complexity of the works.

Ostwind 4's HVDC technology and 110 km cable route mean a coordinated logistics and installation campaign across offshore and onshore works. The project ties into ongoing regional build-out: OstSee Energies is sited near existing wind farms linked by prior Ostwind connections. The packages awarded to large equipment and installation contractors indicate the project is advancing through procurement and pre-construction stages.