Offshore Grid Connection BorWin5: TenneT Awards Contracts For Converter Stations And Cables

• The consortium of Siemens AG and Dragados Offshore S.A. has been awarded the contract for the construction of converter stations on land and at sea, while NKT HV Cables AB has been awarded the contract for the production and installation of the DC underground and submarine cables.
• With 230 kilometres the longest offshore direct current connection to date
• Commissioning of the 900 megawatt connection is scheduled for 2025

In the tendering procedure for the contract to build the longest offshore grid connection sys-tem, BorWin5, with 230 kilometres, TenneT has awarded the contracts for the converter sta-tions on land and at sea to the consortium Siemens AG / Dragados Offshore S.A. The con-tracts for the DC underground and submarine cables have been awarded to NKT HV Cables AB.

“With regard to our latest offshore project, we are delighted to not only award the contract to Siemens and Dragados, two companies that are both proven and innovative in the construc-tion of converters but also to NKT, another powerful supplier in the market for plastic-insulated direct current cables ", said Tim Meyerjürgens, COO of TenneT.

BorWin5 is the 15th offshore grid connection system to be realised by TenneT in the German North Sea and also the twelfth direct current connection.

Tim Meyerjürgens: "With the award of BorWin5, we are proceeding with the continuous cost reduction in the construction of offshore grid connection systems. Compared to the predecessor project DolWin5, we were again able to achieve a significant cost reduction for the converter stations. One reason is that for BorWin5 the smart platform concept is being used for the first time. This not only keeps the costs for the platform construction manageable, but also allows us to extend the intervals for maintenance and servicing to once a year". With the smart platform concept, TenneT is continuing to drive forward standardisation. In accordance with the principle 'as little as possible, as much as necessary', we only install the technology on the offshore platforms that has to be available offshore. In doing so, we make use of the extensive experience gained from the grid connection systems already in operation.

In addition, BorWin5 is the second project after DolWin5, in which the wind turbines are directly connected to the offshore platform BorWin epsilon via 66-kilovolt three-phase power cables. This eliminates the transformer stations that were previously required in every wind farm. In addition, 155-kV three-phase current cables are no longer required to connect the TenneT offshore platform with the wind farm. By means of a 230-kilometre-long extra-high-voltage direct current cable, TenneT transmits the electricity to the Garrel/East converter station on land after conversion using low-loss direct current technology. Here, the direct current is converted back into three-phase alternating current and fed into the extra-high voltage grid. With the 66 kV direct connection, BorWin5 belongs to the new generation of cost-efficient offshore grid connections, which make an important contribution to the energy transition.