London Power Tunnels
a network of tunnels in London carrying high-voltage electricity transmission cables
London Power Tunnels is a project by National Grid to reinforce the electricity transmission network in London, UK, by constructing more than 60 km of new deep-level tunnels carrying high-voltage cables.
The new network of tunnels replaces a series of ageing power cables, most of which were buried directly beneath roads. These were becoming unreliable, difficult to maintain without disrupting traffic and were unable to meet future demand for electricity. The new tunnels allow the power cables to be upgraded and maintained without disruption to traffic and residents on the surface.
The project is divided into two phases: the first phase involved constructing tunnels connecting substations at Wimbledon, Hackney and Willesden and was completed in 2018. The second phase involves linking Wimbledon substation with Crayford and is expected to be completed in 2026.
Phase 1
The first phase involved constructing 32 km of tunnels linking substations from Wimbledon in the south west to Hackney in north east of London, at a cost of £1 bn. The 3–4 m diameter tunnels were dug by tunnel boring machines and run 20–60 m below street level. The tunnels were constructed by a joint venture between Costain Group and Skanska.
This phase linked Wimbledon and Hackney to substations at Willesden, St John's Wood, St Pancras, and Islington.
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