Case study: London Power Tunnels – Specialist Earthing
The National Grid have commissioned some 25 miles of tunnels up to 50m beneath the City of London to house distribution cables from major sub stations to satisfy the increasing demand for power in our ever expanding Capital and eliminate the logistical problems associated with an above ground distribution network. Such an undertaking required a complex earthing network.
Churchill Specialist Contracting have had a continuous site presence for a period of 3 years completing the supply and installation of main equipotential earthing for all 12 Head Houses, Shafts and Pit Bottoms. This is a huge undertaking with all main conductor routes being installed in 50x6mm copper conductor in a complex series of directions and vertically at all levels and undertaking shaft drops in excess of 40m.
Every item of exposed metalwork is connected back to the main equipotential earthing conductor and all hand rail sections are linked via flexible copper braid links.
In addition, a dedicated set of earth electrodes are installed at strategic locations throughout the whole 25 mile series of underground tunnels.