HSM Offshore also to build second TenneT-platform for offshore wind farms

TenneT TSO B.V. has contracted HSM Offshore (Schiedam) for the construction of its Borssele Beta offshore transformer substation (platform). In February of this year HSM had already been commissioned to build the Borssele Alpha platform, and also appointed as the preferred contractor for this project as well. The two platforms are an essential link in building the grid connections for the wind farms to be constructed offshore in the Borssele Wind Farm Zone. These are the first large-scale grid connections for offshore wind energy in the Netherlands to be constructed under the National Energy Agreement.

‘First steel cut’ for Borssele Alpha platform

In addition to signing the Borssele Beta contract, the ‘first steel cut’ for the Borssele Alpha platform took place at the HSM shipyard in Schiedam. This ceremony traditionally marks the start of construction work.

Borssele Alpha and Borssele Beta platforms

TenneT has commissioned HSM Offshore to take care of the engineering, construction, transport, installation, connection and testing of the two offshore platforms.

Borssele Alpha and Borssele Beta both have a connection capacity of 700 megawatts (MW) for offshore wind farms. The Alpha platform is scheduled for completion in 2019, the Beta platform in 2020. TenneT is the operator of the onshore and offshore electricity grid in the Netherlands and a large part of Germany, and is realizing an offshore grid in the Dutch part of the North Sea with a capacity of at least 3,500 MW and five grid connections. From 2019 to 2023, TenneT will take a 700 MW offshore grid connection into operation every year in accordance with a standardized concept, in order to meet the objectives and tight schedule defined in the National Energy Agreement.

Borssele Alpha and Borssele Beta subsea cables

The total length of the route section from the onshore station at Borssele to the offshore transformer stations (i.e. the platforms) is 61 km for Borssele Alpha and 68 km for Borssele Beta. Each of the two offshore grid connections consists of two 220 kV subsea cables with a capacity of 350 MW. In a world first, 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.