London Power Tunnel Highbury 132kV Cables

Project outline

In February 2011 National Grid embarked upon a seven-year £1bn project to reinforce the high voltage network across London by installing new cables and wires via deep underground tunnels.

The new 32km electricity superhighway deep below the capital will help keep Londoners connected to safe and reliable electricity supplies. The project is due to be complete and fully operational in 2018.

The London Power Tunnel (LPT) network runs from Hackney to St Johns Wood, Willesden to St Johns Wood and from Wimbledon to Kensal Green.

Murphy had previously been contracted to construct the 400kV GIS Sub Station at Highbury as part of the EAN Framework and by UK Power Networks to construct a 132kV Primary Bulk Supply Point Sub Station at Islington. This substation would be powered from the NGET Highbury site utilising the newly constructed LPT network.

Murphy installed three 132kV cables and related steelwork between Highbury and Islington, and then Islington and St. Pancras substations. These circuits will connect the two substations that Murphy initially constructed for UKPN as part of the EAN Framework.

Key challenges

The team worked with the client producing a number of collaborative measures to minimise delay. The site team were extremely organised and without their fantastic attitude the quick-turnaround could not have been achieved. 

At the beginning of the work possession of the tunnel was shared, making access a challenge. Murphy collaborated with National Grid and the other contractor involved, both on the ground and at executive level, to create an access plan that worked for everyone. Murphy’s willing attitude and collaborative approach was duly noted by National Grid.

Completion of the 132kV cables works was a critical key programme date for the LPT scheme and any delay would have had a significant effect on the overall National Grid programme. A seven day working week and well-presented programme enabled this challenge to be met.

There was limited parking in the local area and so Murphy discouraged staff from driving to work. Employees were instead asked to park at Murphy’s nearby head office in Kentish Town and use a shuttle bus taking staff to site.

Project delivery and innovations

The works required installation of the longest ever single-length power cables in an underground utility tunnel in the UK, at 2km long.

The teams’ aim was to reduce the amount of joints in the cabling which would be pulled through a maze of culverts and shafts. The system and methodology used was designed and fabricated in house by the Murphy team allowing them to install the cable in the longest section lengths possible. 

The team utilised a surface based hydraulic drum drive unit to control the 30 ton drums, in series with a VSD motorised roller system managing the careful ascent of the conductor from the ground level, through a maze of culverts and down vertical access shafts of up to 50 meters in depth. Once within the confines of the LPT the system was coupled to a mono rail with a further series of VSD rollers permitting the cable to be distributed through the tunnel guided by modified tugs to the point of final layoff. This process facilitated the installation of the longest ever single-length power cables in an underground utility tunnel in the UK, at 2000 meters in one continuous length.

The proprietary system was designed and fabricated in house by experienced Murphy staff, effectively meaning the specialist cable team were able to carry out the project efficiently, on time and at a competitive price.

Key facts

  • Longest single-length cable pull in an underground utility tunnel in the UK (at the time of construction)
  • One circuit of cable installed a week (three cable lengths = one circuit)
  • No accidents or RIDDOR incidents on site
  • Extensive range of plant was used to complete the work, much of which was designed, manufactured and tested in-house.


National Grid


Highbury, London

Completion Date

February 2017



The expertise and experience of the Murphy team has been clear from day one. They have been proactive in providing innovative solutions and working collaboratively with the client. - Mark Farmer Project Manager

Capabilities Demonstrated

  • Power

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