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Operations & Maintenance

We offer two forms of maintenance contracts with a choice of non-intrusive or intrusive programs for voltages from 400V to 132kV

We offer maintenance programs for all sector electricity networks

Sinewave is trusted to look after hundreds of electricity networks across the UK. We have national frameworks in place with private organisations IDNOs, renewable energy sites and many others for inspection and maintenance of their networks and assets.

  • Our in-house O&M teams are prepared to respond to an electrical outage 24/7/365.
  • Our O&M teams are supported by the latest asset-management technology that generates asset information on-site in just minutes.
  • Our huge inventory in spares and repairs is the final link in a supply chain that ensures that we get your site back online as quickly and safely as possible.
  • Our work conforms to the standards set forth in the electricity at work act (1989), ESQCRs, HSG 230 and BS 6626:2010.

Operations & Maintenance

Our maintenance programs are designed to ensure that your substation plant, switchgear and transformers are performing at their optimum working condition. They also serve to keep your site 100 percent compliant with all current safety regulations.

Two Forms of Contracts

Our electrical fitters and Senior Authorised Persons will perform all required tasks within the agreed scope of work using the latest technology available for “non-intrusive” inspections and maintenance work.

Control, Operate & Maintain Agreement (COMA)

This contract was created for facilities that do not have a high-voltage Authorised Person on-site.

Maintenance Only

This contract was created for sites that have a high-voltage Authorised Person available on-site at all times.

case study

Dartford Tunnel - TFL and Connect Plus Services

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Non-intrusive inspections encompass

  • General building inspection Inspect all earthing connections, labelling, substation cable pit, heating, ventilation and dehumidifiers
  • Substation plant general condition assessment Oil leaks, rust, external weed clearance, etc.
  • Partial discharge detection transient earth voltages and ultrasonic detection
  • Thermography (thermal imaging)
  • Visual inspection and interrogation of protective relays
  • Ensure labels are legible and compliant on all high-voltage and low-voltage equipment
  • Take oil samples and conduct routine oil testing moisture, breakdown voltage, acidity, colour coding, dissolved gas analysis
  • Battery and chargers testing
  • Comprehensive inspection reports

Planned preventive maintenance encompasses

  • Oil circuit breakers and switchgear
  • SF6 (Sulphur hexafluoride) circuit breakers and switchgear
  • Vacuum circuit breakers and switchgear
  • Transformers, both fluid-filled and dry type
  • High-voltage (oil-filled) voltage regulator
  • Overcurrent relays, earth fault, G59 and other protective relay testing
  • Substation earthing
  • Low-voltage circuit breakers
  • Power factor correction units
  • Voltage optimiser units
  • Battery and chargers testing
  • Comprehensive maintenance report

In addition to the inspection contract, we also provide:

  • 24/7/365 emergency call-out service
  • Serving as Authorised Person (if required)
  • Technical support
  • Signage posted on each substation door showing 24-hour emergency contact information
  • Comprehensive report with details of all work completed
  • NEDeRS® information on your substation plant (see explanation below)


Sinewave subscribes to the ‘National Equipment Defect Reporting System,’ abbreviated as NEDeRS®. It allows us to gain access to an international database of 47,000 reports of electrical equipment defects from service providers, industrial users and electrical equipment manufacturers.

NEDeRS® is available to asset owners, network operators, and maintenance and support organisations, but not to manufacturers. Subscribers gain unlimited access to the NEDeRS® web pages and receive information by email whenever a defect report is issued.

The comprehensive database enables subscribers to conduct historic searches by plant and specific manufacturers. The system contains photographs, diagrams, associated documentation and contact numbers for most of the plant items registered within its pages. The scheme avoids delays from manufacturers in notifying users of potential problems, thus saving time and money, and identifying safety issues as quickly as possible.

Fault Location

Sinewave’s emergency response service operates 24/7/365 attending to high-voltage and low-voltage faults nationwide. The goal of our service is to have a specialist team mobilised to the fault location within four hours, depending on the geographic location.

Each emergency response team consists of at least one Senior Authorised Person who can carry out fault switching and restore supplies. The team will assess the fault and offer advice on the best course of action to remedy the situation. (See FAQs)

  • Using the latest portable fault-location equipment and software, we can quickly establish where a cable fault as occurred.
  • We have all the trade disciplines in-house to locate faults, isolate the HV network, excavate, and perform jointing works to repair the cable.
  • We offer a complete turnkey solution from engaging our services to the restoration of supplies and reinstatement.
  • If it’s impossible to make a swift repair, we can connect a temporary generator to support your power needs as repairs are being made.

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