TenneT Awards Retrofit Contract for German Offshore Converter Station

March 19, 2025, by Adnan Memija

Bluestream Offshore, a subsidiary of OEG Energy, has been awarded a contract by transmission system operator (TSO) TenneT for the retrofit installation of a corrosion protection system on the SylWin alpha offshore converter station for the SylWin1 offshore grid connection in Germany.

The award is for the subsea installation of an Impressed Current Cathodic Protection (ICCP) system to replace the existing faulty ICCP system.

The replacement includes the decommissioning of outdated cables and debris that cause system interference, alongside a pre-survey, which will be conducted using a remotely operated vehicle (ROV)-mounted multibeam sonar, and visual inspections to assess the condition of the work area to identify obstructions.

For the installation of the new ICCP system, Bluestream will route and secure subsea cables through the J-tube, install and connect three ICCP buoy-mounted anodes, and ensure proper ICCP positioning around the jacket structure, said OEG.

Concrete mattresses will be laid to protect and stabilize the newly installed cables, and the system will then undergo commissioning, functional testing, and an as-left survey to verify full operational integrity.

The work scope will be executed from a DP-2 Dive Support Vessel (“DSV”) equipped with a walk-to-work system, utilising a 24/7 offshore crew of divers, ROV pilots, and supervisors for the subsea installation. The DP-2 DSV will also be mobilised with a full diving equipment spread and an ROV equipped with cameras, a multibeam imaging sonar, and a manipulator skid for precision tasks, alongside a dedicated rigging workshop.

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In April 2015, TenneT commissioned SylWin1, currently the longest offshore grid connection in the world, according to the TSO.

SylWin1 connects three offshore wind farms, located 70 kilometres off the coast of Sylt, to the mainland. The projects include the 288 MW Sandbank, the 288 MW DanTysk, and the 288 MW Butendiek.