Constructing the Cleve Hill Substation
The main construction activities that have been completed at Cleve Hill are outlined below.
Earthworks and landscaping
The main earthworks operation, carried out in 2009, involved creating a plateau on the sloping hillside to enable us to build the substation’s foundations; 150,000m3 of excavated material (earth and rocks) was used to form screening mounds to reduce the substation’s visual impact. So far, we’ve planted 10,000 trees and shrubs on the mounds.
National Grid Compound
A 400kV compound was built and is operated by National Grid. It consists of:
- An overhead line landing compound, where one circuit of the overhead power line was brought down to two steel lattice gantries. This connection from the substation to the national transmission system was completed in September 2011.
- A building containing switchgear and related equipment as well as auxiliary services such as a workshop area and welfare facilities for staff.
The London Array Compound
Constructed by London Array Ltd, this consists of:
- The North Wall, designed by RMJM Architects. This screens the substation from view from the Saxon Shore Way as well as making the design fit better with the surrounding landscape.
- Four transformers which boost the power imported from the offshore substations to 400kV so it can be fed into the national transmission system.
- An open area for electrical equipment, including power conditioning apparatus.
- An auxiliary services building which has been built in the same style as the National Grid compound’s switchgear building.
- Fire deluge pump house and tank.
- The four export cables, connecting the offshore substations to the substation at Cleve Hill, which were installed in 2011 and 2012.
- Construction operations on the site were completed in 2012 and the site is now fully operational.
Due to legislation changes, on completion, London Array’s transmission assets (the onshore and offshore substations and associated cables) will be owned by an independent Offshore Transmission Owner. London Array Phase One (630 MW) is part of Ofgem’s second transitional tender round for the ownership and operation of its transmission assets, which kicked off on November 2010. The OFTO is appointed by Ofgem, after a tender exercise Blue Transmission was announced as the preferred bidder for London Array’s transmission assets. Blue Transmission is a joint venture of financial and technical organisations and they are already and OFTO for another offshore wind farm. We expect the sale will be completed later this year.
We have installed permanent light fittings around the main plant. These will only be used for maintenance work during the hours of darkness; the site will not normally be lit.
The substation needs permanent external fencing to a specified security standard for this type of installation.
- The 4km of fencing is around 2.4m high and has additional security features.
- Internal fencing separates the various compounds within the substation.
- The site has similar security arrangements to other National Grid substations.
The main asphalt access road, together with a security gate and associated features at the site entrance, were completed in 2012.