Offshore construction
Offshore cabling
Specialist offshore cable laying vessels will be used to install the offshore subsea electricity cables. There are two types of subsea cables - 'export cables' and 'inter-array cables'.
The export cables take the electricity from the offshore substation to the landfall point at Carnoustie.
The inter-array cables form a network within the wind farm site and take the electricity generated by the wind turbines to the offshore substation.
In both cases, the cables are installed by the specialist vessels following careful survey and route clearance. The aim is for cables to be buried wherever possible, however, where this is not possible due to seabed conditions, cables will be protected using rock placement.
The manufacture and installation of the offshore cabling provides significant employment and business opportunity.
Image: The Nexans Aurora cable installation vessel at Seagreen (C) Nexans.
Offshore substation
The offshore substation is essentially the backbone of the wind farm, taking the electricity generated by the turbines and converting it to the voltage required for onward transmission to the onshore substation at Tealing.
The substation (installed in January 2022) is secured to the seabed via a 5,100t jacket substructure, which will play a critical role in safely supporting the substation topside above the sea during Seagreen's 25-year operational lifespan.
With a 43m x 43m footprint, the jacket has built in tubing designed to guide the incoming 15 inter-array cables bringing the electricity generated by the turbines to the substation. There is additional tubing which guides the three outgoing export cables from the substation to the seabed.
The 4,800t topside was installed in March 2022, measuring in at 40m long, 45m wide and 15m high. The complete structure of topside and jacket foundation sits in water depths of around 55m and will be one of the largest AC platforms in UK waters.
Image: The Seagreen offshore platform (yellow) with supporting cable and commissioning vessels. June 2022.
Turbine installation
The installation of the turbines is being undertaken by the specialist heavy lifting vessels Wind Osprey and other support vessels. Such support vessels include local fishing vessels who are employed as guard vessels throughout the offshore construction phase ensuring a safe construction zone for all marine traffic.
