Deep below the streets of London, ABB is installing Europe’s longest 400kV XLPE underground cable
ABB’s three-year project to help National Grid deliver more power to central London reached a key stage as the 400kV cable started the 20km underground pull from Elstree to St John’s Wood.
The £40 million turnkey project, known as ‘The London Connection’, is part of National Grid’s programme to upgrade the power grid for North West London and the City area. Running in a 20km long, three-metre diameter tunnel the largest tunnelling project that National Grid has ever undertaken the cable will link an extended substation at Elstree to the new indoor high-voltage GIS (gas insulated switchgear) substation, which ABB has been building at St John’s Wood.
The 400kV connection is using ABB’s high-technology cross-linked polyethylene (XLPE) insulation technology, which requires less maintenance. A similar ABB underground cable installation has been in service in Berlin since 1998.
ABB is supplying, installing, commissioning and testing 61km of 150mm diameter cable, weighing a total of 2,440 tonnes and delivered on 63 massive drums. The cable is being laid as three separate lengths, one for each phase of the three-phase electricity supply. The project is scheduled for completion in June 2005. The tunnel allows space for a second 400kV cable circuit in the future should London’s demand for electricity increase even further.