VESSEL REVIEW | DolWin Epsilon – Offshore converter platform to support power distribution in northern Germany
Dutch/German transmission system operator TenneT recently acquired a new HVDC converter platform.
The 84-metre (280-foot) high, 27,000-ton DolWin Epsilon platform was constructed by consortium partners Aibel and Seatrium as part of the DolWin5 project for TenneT. The platform is installed in the North Sea 60 kilometres (37 miles) off Borkum Island and has a transmission capacity of 900 MW, which would be enough to supply electricity to up to 1.1 million households in northern Germany.
Transmission support infrastructure to benefit an estimated one million users
DolWin Epsilon was completed and commissioned in close collaboration with Hitachi Energy, which designed, delivered and installed the HVDC equipment including the converter valves, transformers and high voltage switchgear.
The platform will convert electricity generated from the Ørsted-operated Borkum Riffgrund III offshore wind farm. The electricity will then be transported to the transmission grid on the mainland via a 100-kilometre (62-mile) undersea cable and a 30-kilometre (19-mile) onshore cable.
Through the use of extra-high voltage direct current transmission technology, the platform converts the 66kV three-phase alternating current (AC) generated by the Borkum Riffgrund III wind farm into 320kV direct current (DC) before transporting it to an onshore converter station at Emden/Ost with little loss.
The onshore station converts the DC back into AC before feeding it into the onshore grid. This setup eliminates the need for a windfarm substation.
Enhanced safety features
The platform is equipped with a VCE permanent measurement system for structural health monitoring for its service life. Glamox meanwhile supplied 2,084 marine-grade luminaires as well as the systems to remotely monitor and test the onboard emergency lighting.
As the platform will be unoccupied most of the time, the lighting is needed primarily for remote inspection and for visiting crews and maintenance teams.
Although intended to operate without an embarked crew, DolWin Epsilon has accommodation for up to 50 personnel, a helicopter deck, a lifeboat, and a Liebherr offshore crane with a lifting capacity of 35 tonnes for supply and maintenance functions.
The platform itself is a gravity-based structure; it is anchored to the seabed by its own weight alone.
DolWin Epsilon was constructed over a period of more than three years. Following completion of the main platform at Seatrium’s facilities in Singapore, it was transported via heavy-lift ship to Aibel’s shipyard in Haugesund, Norway, where its high-voltage electrical equipment was installed as part of the final commissioning process.
The platform was later transported self-floating and installed at its final destination in the North Sea. Seatrium said it was designed to have an operational life of 30 years.
