PRS has been commissioned to design 4 new substations as part of the power upgrade of the Sub-Surface Lines for London Underground.

Over the next ten to fifteen years, all the lines on the London Underground network will be upgraded as part of the Public Private Partnership (PPP) contracts, the most extensive of which is the upgrade of the Sub Surface Lines (SSL), comprising the Metropolitan, Circle, District and Hammersmith & City Lines. Although the SSL upgrade is being undertaken by Metronet SSL, London Underground is obliged by the PPP contract to provide the increases in power necessary to support the upgrade.

Upgrading the SSL network is planned to begin in 2009 with the introduction of new rolling stock on the Metropolitan Line, and is to be completed in 2016, when the last of the present rolling stock on the District Line will be removed from service.

The new ‘S’ stock trains that are to be introduced on the SSL network have a higher power rating than the existing fleets, owing to increased tractive effort and larger auxiliary loads (air-conditioning etc.), which, together with an enhanced timetable, increase the power demand on the present SSL power supply infrastructure.

To support the increased load, the substations along the route of the Metropolitan Line between Amersham, Watford, Uxbridge and the new eastern terminus at Barking need to be upgraded to increase their rating; and new traction substations will be provided and a bulk supply point at Edgware Road. PRS are designing and obtaining planning consents for the new sub-stations at Edgware Roaf, Farringdon, West Ham and Upton Park.