Northern line power upgrade (NLPU)

Northern Line power upgrade works at Stockwell station
Balfour Beatty Rail
Stockwell, Mile End and Whitechapel, London
Nov 2020
Apr 2021

We carried out civils, premises and fire stopping elements of works as part of the Northern Line power upgrade.

The NLPU involves upgrading existing infrastructure at key locations across London as part of the high voltage (HV) power network upgrade.

VGC Projects carried out key elements of the upgrade at three key sites: Stockwell, Mile End and Whitechapel.

Stockwell substation

Northern Line power upgrade package 2 temporary stairs
Access stairs for the temporary transformer base at Stockwell substation

Our contract was to upgrade the infrastructure for the substation’s two power transformers.

We built a temporary base to house the first transformer, while we upgraded its pen.

After a new transformer was commissioned in the first renovated pen, we moved the second transformer onto the temporary base. Then we carried out the renovation of the second pen.

At the end of the works, we removed the temporary base and reinstated the area.

Risk control

All personnel on site obtained full security clearance, and received training to work in the live high-power sub-station environment.

Like our signalling equipment room project at Farringdon station, this is a Beacon site. Regular inspections from Balfour Beatty’s health and safety team returned consistent excellent feedback.

Temporary base scope:

  • reinforced concrete slab
  • drainage channel
  • brick bund wall
  • palisade fence and gates
  • access steps

Pen upgrade scope:

NLPU package 3 pen A
Transformer pen during upgrade
  • reinforced concrete foundations
  • wall demolition
  • install ACO drainage channel
  • reprofile the drainage floor
  • fix holding bolts for steel work
  • low level walkway
  • high level walkway

Mile End substation

At Mile End we de-commissioned an old transformer on the first floor, and installed a new transformer on the ground floor.


  • new screed floor for transformer
  • widening the doorway
  • temporary works
  • screed ramps
  • core holes

Whitechapel substation

Our project at Whitechapel substation consists of minor works to enable new switch gear panels to be added to expand the existing capacity.


  • core holes
  • screeding the new floor
  • painting and finishing

Balfour Beatty’s senior project manager thanked the team, including Cosmin Simion and Mihai Gligor, for their hard work, commitment and quality of workmanship.