Our high voltage capability and expertise enables us to offer a full end to end project and maintenance service offering, on systems from 11kV up to 400kV. This includes power generation, transmission and distribution right across the UK and Northern Ireland.

Our maintenance service offering includes routine overhauls of transformers and switchgear at all voltages, power transformer refurbishment, component replacements and upgrades.

Our services include:

  • Replacement of switchgear and transformers
  • Complete build of new substations
  • Plant removal and installation
  • Cabling and jointing
  • Relay panels
  • SCADA systems
  • Protection work
  • Execution of system outages and undertake full commissioning.
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Scottish & Southern Energy Networks (SSEN)


Primary Substation, 11kV Switchgear Replacement


Asset Replacement


Distribution Network Operator (DNO)



The Brief

The Primary substation occupies a congested site surrounded by extensive area of redevelopment for housing.  The existing double busbar switchgear was of an old manufacturer and subject to ongoing issues with reliability and spares availability.

SSEN required that we undertook both Principal Designer and Principal Contractor roles for the Detailed Design and Construction of a replacement HSS Eclipse 11kV Switchboard in the existing 11kV switchroom.

The Approach

The existing site comprised 2 x 33/11kV Primary Transformers, and a combined single storey building housing Protection and Control equipment room, with a separate 11kV switchroom. The switchroom had an internal dividing wall with sections of the 11kV switchboard installed to each room with busbars traversing the internal wall.

We chose to install a stand-alone temporary switchboard in the main compound, and then changed out half of the switchboard at a time. Use of the temporary board safeguarded CI/CML exposure and simplified the overall changeout process.

The Delivery

Delivery was undertaken by a dedicated team who coordinated installation of temporary switchgear, circuit transfers, old switchgear removal, civil modifications and subsequent installation of the replacement switchgear sections.

By undertaking multiple 11kV circuit transfers over shortened periods we were able to deliver the 11kV switchgear change works well in advance of target and the associated 33kV supply switchgear works at the source substation.