Construction

Onshore work
Construction of the substation close to Leiston is complete. The substation is where the electricity generated by Greater Gabbard wind farm will be connected to the national electricity transmission system – via the existing 400 kV power lines. The underground electrical cables, which transfer the electricity from the new substation into the existing transmission system adjacent to Sizewell, are in place.

Underground ducts have also been constructed from the beach area at Sizewell to receive the three subocean cables from the wind farm.
 
Offshore work
TThe 140 wind turbine foundation monopiles for Greater Gabbard wind farm are being driven into the seabed on a grid. This involves using of one of Europe's largest construction vessels. Each monopile is a long and robust metal cylinder around 60 metres in length and 700 tonnes in weight. The monopile have a transition piece fitted above the water level. Each transition piece is painted yellow for shipping navigation purposes and then supports the wind turbine tower.

The components for the wind turbines are coming into Harwich from Denmark. To construct a turbine, the barge manoeuvres alongside the foundation, lowers its legs to the seabed and then starts to raise itself hydraulically - jack up. Using the onboard crane, the turbine tower is lifted into place, followed by the nacelle - the 'box' which sits on top of the tower containing the generator, the hub - the cone-shaped piece on the front of the turbine, and the three blades.

A wind turbine tower consists of two sections of long tube, with one fitted on top of the other to form a single column. Access to the nacelle is gained via ladders or a lift up through the tower.

There are two offshore substation platforms – which contain electrical switchgear and transformers to step the voltages from 33 to 132 kV. These will be manufactured and commissioned from UK manufacturers, one in Hartlepool and the other in South Shields. The first of these two platforms (the Gabbard) is nearing completion and will be floated out by barge and installed imminently. Work on the second platform (the Galloper) should be completed in 2010.