TenneT concludes first contract for subsea cables for offshore grid

TenneT TSO B.V. has contracted a consortium consisting of Boskalis subsidiary VBMS and NKT to supply and install the subsea cables that will be used for the grid connections of the wind farms to be built offshore at Borssele in the south-west of the Netherlands. The contract signed on 8 November 2016 concerns the cables for the Borssele Alpha wind farm area. The VBMS/NKT consortium is also the intended partner for TenneT’s next offshore grid connection project, Borssele Beta.

Marco Kuijpers, Senior Manager Offshore Netherlands at TenneT, is pleased with the signing of the contract: ‘It is good to see that our international tender procedure was completed entirely according to plan, and in line with the ambitious cost reduction targets laid down in the National Energy Agreement. Together with the VBMS/NKT consortium, we will set to work on the construction of the first large-scale offshore grid connection for wind farms in the Dutch sector of the North Sea. This project will make a significant contribution to the realization of the Dutch government’s ambitions for renewable electricity generation as laid down in the National Energy Agreement.’

About the subsea cables

The total length of the route section from the onshore station at Borssele to the Borssele Alpha offshore transformer station (the “platform”) is 60 kilometres. The offshore grid connection consists of two 220 kV subsea cables with a capacity of 350 MW each. The cables’ so-called “dynamic capacity” will be utilized. This means that a single cable can be temporarily subjected to a load of up to 380 MW.

The cables will be installed in the seabed of the Western Scheldt estuary and will run to the onshore high-voltage station at Borssele. The cables will be installed at a depth of 1 metre in the North Sea, and at a depth of 3 metres along the entire route in the Western Scheldt estuary, up to the point where they come onshore at Borssele. In some locations the cables will be installed at even greater depths to cope with possible seabed movements.

The VBMS/NKT consortium will be responsible for the engineering, production, installation and burial of the 220 kV subsea and land cables between the onshore station and the Borssele Alpha offshore platform.
The Borssele Alpha platform will have a connection capacity of 700 MW for offshore wind farms and is scheduled for completion in 2019. The Borssele Beta offshore platform is expected to be completed by 2020. TenneT has been officially designated as the offshore grid operator in the Netherlands, and will contribute to fulfilment of the National Energy Agreement by developing offshore grid connections with a total capacity of at least 3,500 MW during the period until 2023. These connections will be constructed in accordance with a standardized concept and will have a capacity of 700 MW each.

The tenders for the subsea cables and offshore transformer stations for the Holland Coast South project will be announced end of 2016.