Substation Maintenance

Substation Maintenance

We have over 2500 national High Voltage (HV) connected sites under contract and an average growth of 200 sites per annum.

SPEC Ltd are a high voltage installation and maintenance company specialising in contracts to look after customers high and low voltage equipment whilst taking on the role of Authorised Person duties if the customer does not have anyone trained at high voltage.

SPEC Ltd maintenance work is conducted in accordance with BS 6626: 2010, Maintenance of Electrical Switchgear and Control Gear for voltages above 1 kV and up to and including 132 kV.

SPEC Ltd offer two forms of contract; the first is a Operate & Maintain, where these are geared towards sites that don’t have an HV Authorised Person. The second type of contract is purely maintenance only where generally the sites have their own HV Authorised Person.

Both contracts include an annual visual inspection and 24 / 7 / 365 fault/emergency response.

For the annual charge, SPEC Ltd would:

  • Take on the role of Authorised person for that site. (If required).
  • Provide a 24 / 7 / 365 call out service.
  • Carry out a yearly inspection; this is carried out by one of our Engineers. A copy of the inspection sheet is left on site and a full detailed written report issued to the Contract Manager. This would highlight any problems associated with the equipment under contract and costings to repair.
  • A free partial discharge check would be carried out using a hand-held partial discharge tester. (UltraTEV+).
  • A company call out sign would be fitted to the door of each sub-station giving the 24 hour call out number and the office number for more planned works.
  • An up to date single line HV diagram can be provided for mounting in each substation. (Requirement of AP Duty).
  • SPEC Ltd. are members of the Electricity Association Database on electrical equipment defects ensuring your equipment is covered with the latest information on dangerous incidents notices (DINS) and suspension of operational practices (SOPS), this ensures our switching Engineers are not put at undue risk.

For the maintenance charge SPEC Ltd would:

  • Carry out HV Switchgear, LV Switchgear, Protection Device, PFC Equipment, Transformers and DC Battery charger maintenance, on all equipment under contract and in line with the maintenance schedules agreed.
  • Take oil samples of each transformer and issue a sample certificate on the Routine and Dissolved gas condition. If no PCB records can be produced then this will include PCB and on main Power or critical transformers Furans testing can be completed as the norm.
  • SPEC’s knowledge and support in the Substation Measured Term Planned Preventive Maintenance field will undoubtedly extend the life expectancy of any installed substation which for our clients ensures major savings in down time and repair costs. By carrying out PPM at regular intervals, SPEC are able to detect potential problems and mitigate the higher risk of losing plant which means unforeseen losses to our clients.


  • 24 / 7 / 365 fault response
  • Complete extension panels (single or double busbar) with vertically isolated VCB without the need for busbar adaptor chambers/joggle chambers.
  • Over 2000 national High Voltage connected sites
  • Voltage ranges up to 132kV
  • UK and Worldwide

24/7 call out service.
Available 365 days of the year.