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 is now complete and 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.
- Presently four transformers will 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, were installed in 2011 and 2012.
- Construction operations on the site were completed in 2012. Commmissioning and maintenance activities will continue through 2012 and into 2013.
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 operator. 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.
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. Temporary mobile lighting may also be used in some circumstances. Once the site is fully operational there would be no need for temporary lighting.
The substation needs permanent external fencing to be built to a specified security standard for this type of installation.
- The 4km of fencing will be around 2.4m high and will have additional security features.
- Internal fencing will separate the various compounds within the substation.
- The site will have 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.