London Power Tunnels

London Power Tunnels is a project by National Grid plc to reinforce the electricity transmission network in London, UK, by constructing more than 60km of new deep-level tunnels carrying high-voltage cables.

London Power Tunnels
Location
CountryUK
ProvinceGreater London
Ownership information
OwnerNational Grid plc
OperatorNational Grid plc, UK Power Networks
Construction information
Construction started2011
Expected2026
Construction cost£1bn (phase 1), £750m (phase 2)
Technical information
TypeUnderground tunnel
Type of currentAC
Total length60 km (37 mi)
AC voltage400 kV, 132 kV

The new network of tunnels replaces a series of ageing power transmission cables, most of which were buried just beneath the road surface. These existing cables were becoming unreliable, difficult to maintain without disrupting traffic, and were unable to meet future demand for electricity in London. The new tunnels allow the power cables to be upgraded and maintained without disruption to traffic and residents on the surface.[1]

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.[1] The second phase involves linking Wimbledon substation with Crayford, and is expected to be completed in 2026.[2]

External video
Inside the hidden 'power tunnels' of London, BBC video

Phase 1
Map of London Power Tunnels phase 1

The first phase of the London Power Tunnels project, costing £1bn, involved the construction of 32km of tunnels spanning between the National Grid substations at Wimbledon in south west London and Hackney in north east London.[3] The 3-4m diameter tunnels were dug by tunnel boring machines and run 20-60m below street level.[4] The tunnels were constructed by a joint venture between Costain Group and Skanska. [5]

This phase linked Wimbledon and Hackney with existing substations at Willesden, St John's Wood, St Pancras, and Islington. It also involved the construction of two new substations: one at Seven Sisters Road in Highbury, and another at Kensal Green to feed traction power to the Crossrail project.[6][7]

As well as the main 400 kV power transmission circuits for the National Grid, the tunnels also carry 132 kV circuits from Islington substation to St Pancras and Seven Sisters Road, which form part of the London power distribution network operated by UK Power Networks.[8]

The project was started in February 2011 and the first section was energised five years later in February 2016. The project was officially opened by Prince Charles in February 2018.[9]

Phase 2

The second phase (known as LPT2) is due to start in spring 2020 at a cost of £750m, and will span 32.5km from Wimbledon substation to Crayford in south-east London.[10] The tunnels will be between 3m and 3.5m in diameter, and will be constructed 10-63m below street level, with the majority of the tunnel being around 30m deep.[11] The contract for digging the tunnels for this phase was awarded to a joint venture between Murphy Group and Hochtief in December 2019.[12][13]

This phase aims to link Wimbledon substation to existing substations at New Cross, Kidbrooke, and Hurst, with intermediate shafts being built at Eltham and King's Avenue in Brixton.[14]

Phase 2 is expected to be completed by October 2026.

References
  1. "London Power Tunnels". National Grid (Press release). Retrieved 13 January 2020.
  2. "London Power Tunnels 2". National Grid (Press release). 3 April 2018. Retrieved 13 January 2020.
  3. "£1bn London Power Tunnels project opens". New Civil Engineer. 9 February 2018. Retrieved 13 January 2020.
  4. "Rewiring London". Power Technology. 12 March 2013. Retrieved 13 January 2020.
  5. "Keeping Londoners connected to a safe and reliable electricity supply". Costain (Press release). Retrieved 26 January 2020.
  6. "Energising London's £1bn energy superhighway". ABB (Press release). 23 July 2018. Retrieved 13 January 2020.
  7. "Morgan Sindall's canal collaboration builds new London substation". Construction News. 23 October 2015. Retrieved 13 January 2020.
  8. "London Power Tunnel Highbury 132KV". Murphy (Press release). Retrieved 17 January 2020.
  9. "Tunnel vision lets Charles get hands on power at last". The Times. 8 February 2018. Retrieved 13 January 2020.
  10. "Project summary". Retrieved 13 January 2020.
  11. Martin, Karen. "New London cable tunnel in the bidding". TunnelTalk. Retrieved 2020-02-13.
  12. "National Grid award contract to deliver second phase of London Power Tunnels". London Power Tunnels (Press release). Retrieved 26 January 2020.
  13. Knutt, Elaine (19 December 2019). "Contract signed on 32.5km London Power Tunnel Phase 2". Network. Retrieved 31 January 2020.
  14. "Tunnel Route". Retrieved 13 January 2020.

See also
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