A consortium comprising Siemens and Dragados and cable company NKT have been awarded contracts to deliver TenneT’s 900MW BorWin5 offshore wind connection in the German North Sea.
The construction partnership will build the converter stations on land and at sea, TenneT said, while NKT has been selected on the turnkey deal to supply and install cabling.
The latter deal is worth below €250m, the cable manufacturer said. The power cables have an expected production start end-2021.
BorWin5 will connect the EnBW He Dreiht wind farm to the transmission network and is the longest offshore grid connection at 230km.
The commissioning of BorWin5 is planned for 2025.
TenneT chief operations officer Tim Meyerjurgens said: “We are delighted to have awarded Siemens and Dragados, two well-established and innovative companies in converter construction, and at the same time to commission another high-performance service provider from the plastic-insulated DC cable market for our latest offshore project.”
BorWin5 is the fifteenth offshore grid connection system implemented by TenneT in the German North Sea, and the twelfth which is a direct current connection.
Meyerjurgens added: “With the award of BorWin5 we are continuing the continuous cost reduction in the construction of offshore grid connection systems.
“Compared to the previous DolWin5 project, we were again able to achieve significant cost reductions for the converter stations. One reason for this is that BorWin5 is using the smart platform concept for the first time.
“This not only keeps the costs for the platform construction manageable, but we can also extend the maintenance and repair intervals to once a year.”
In addition, BorWin5 is the second project after DolWin5 in which the wind turbines are connected directly to the BorWin Epsilon offshore platform via 66 kilovolt three-phase cables.
This negates the need for transformer stations in every offshore wind project.
TenneT said 155 kV three-phase cables are no longer required to connect the offshore platform to that of the wind farm.
After conversion, TenneT will use a 230km high-voltage direct current cable to transmit the electricity to the Garrel / Ost converter station on land using low-loss direct current technology.
Here the direct current is converted back into three-phase current and fed into the extra-high voltage network.
In addition to the BorWin1, 2 and 3 projects, BorWin5 is the fourth offshore grid connection that TenneT has implemented using high-voltage direct current transmission technology off the coast of Borkum, Germany.
NKT president and CEO Alexander Kara said: “Over the past years, NKT has established itself as a key partner in the green transformation of Europe.
“We have completed a number of power connections ensuring transmission of renewable energy and during 2020 we were awarded more interconnector projects as well as this new offshore wind farm connection in Germany.
“The BorWin5 project win proves the value of our long-term collaboration with TenneT and confirms our strong position as a high-voltage DC solution provider.”
The award of the BorWin5 project does not change the 2020 financial outlook for NKT.