Siemens will supply the electrical equipment for two offshore substation platforms, which will be installed at the wind farm. The substations will bundle the power generated by London Array’s first 630 MW phase, which will use 175 Siemens SWT-3.6 wind turbines, before it is transported via high-voltage subsea cables – to be supplied by Nexans - to the coast. Each of the platforms will have two 180-MVA transformers and medium-voltage switchgear along with requisite protection, instrumentation and control equipment. Siemens says that distribution over two platforms has the advantage that the cable routes within the wind farm are short, allowing power transmission losses to be kept as low as possible.

The transformers on the substation platforms step up the 33 kilovolts (kV) generated by the wind turbines to a transmission voltage of 150 kV. High-voltage subsea cables will transport the electricity to the grid access point, which is located in Cleve Hill. In addition to a substation with four 180-MVA power transformers (400/150 kV) Siemens will also install four 50-MVAr reactive-power compensators at this access point to fulfill the UK grid code on the quality of the electrical energy fed into the grid.

Siemens says it will deploy its new SVC Plus system, which operates with voltage-sourced converter (VSC) technology and is continuously controllable with the aid of insulated-gate bipolar transistors (IGBTs).

Siemens will also prepare the requisite design studies for grid access for all of the wind farm’s electrical components and prepare the grid studies to demonstrate fulfillment of grid access requirements.

“Offshore wind farms of this size place particular demands in terms of grid access,” said Udo Niehage, CEO of the Power Transmission Division of Siemens Energy.”

The London Array wind farm is being built in the Thames Estuary around 20km from the Kent and essex coasts by Dong Energy, E.ON and Masdar, who expect to the have the first 630MW phase operation in 2012. The partners will also have an option to extend the wind farm to its orginally envisaged 1GW of capacity, enough to supply almost a quarter of the population of Greater London.