TenneT’s 900 MW German Offshore Grid Connection System Fully Energised

The Dutch/German transmission system operator (TSO) TenneT Germany has commenced the commissioning of the 900 MW DolWin5 offshore grid connection system.

Following the completion of the installation campaign in the summer, the consortium of Aibel and Seatrium, together with Hitachi Energy and TenneT, started commissioning as planned in the autumn, said the TSO.

In addition to the complete HVDC and cable installation by Prysmian, all relevant ancillary systems were also commissioned on time.

After the successful undervoltage setting of the converter and the HV components, the dynamic tests were carried out. DolWin5 is now fully energised with a transmission capacity of 900 MW.

The offshore grid connection uses extra-high voltage direct current (HVDC) transmission technology. The three-phase alternating current (AC) generated by the Borkum Riffgrund 3 offshore wind farm will be converted into direct current (DC) at DolWin epsilon and transported south to Hamswehrum near the river Ems in East Frisia via the 100-kilometre-long subsea cable.

From Hamswehrum, a 30-kilometre-long onshore cable leads to the converter station in Emden/East, where the DC will be converted back into three-phase AC and fed into the extra-high voltage grid on land.

The installation of Siemens Gamesa 11 MW turbines at the Borkum Riffgrund 3 offshore wind farm was completed at the beginning of this year.

The project was planned to be commissioned at the end of 2025, but was postponed to the first quarter of 2026 due to a delay in the grid connection construction.

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