Maintenance
ESE provides both planned preventative maintenance (PPM) & reactive maintenance contracts to ensure your high voltage apparatus remains operationally safe, compliant and reliable. Where required, we can also act as an Authorised Person, managing safe operation, inspections and testing as part of your tailored maintenance package.
Contract options include:
- 24/7, 365-day call out
- Annual visual inspection of all HV apparatus
- Report detailing any defects & proposed reactive measures
- Testing & verification of correct operation of protection relays
- Oil sampling
- Desiccant breather replacement
- Full Health and Safety substation signage
- Partial Discharge (PD) monitoring
- System diagram installed in every substation
- Supply of generators in the event of our standby engineers being unable to restore power
Our engineers
Our engineers are available nationwide in the event of a loss of power. They also carry out cable location and fault finding, so that any issues are found and resolved as quickly as possible. We hold a large stock of transformers and switchgear at our Leeds depot, greatly reducing procurement lead times & disruption on site.
Find out how we can help you.
Partial discharge testing
Partial Discharge (PD) is widely recognised as one of the best early warning indicators of deterioration in primary insulation. ESE carry out PD testing as part of every maintenance contract to highlight incipient faults in HV insulation before they lead to failure.
Benefits include:
- Supports condition-based maintenance planning
- Helps avoid unplanned outages & improves network resilience
- Provides baseline PD readings to assess insulation & installation quality
- Improves safety, particularly for switchgear, outdoor HV plant & cable sealing ends
- Helps extend asset life & delay capital replacement
Frequently Asked Questions
Frequently Asked Questions
Oil sampling is included within our maintenance packages and can usually be carried out with the equipment live, so there is no disruption to site operations. Samples are analysed by an industry-recognised laboratory, and we provide a clear report on the results.
To provide an accurate quotation, it is helpful if you can share:
- HV network diagrams, if available
- Previous HV maintenance records for the equipment
We operate across mainland United Kingdom.
We offer two HV maintenance packages – Comprehensive & Priority.
Comprehensive
- Annual inspection by an HV maintenance engineer and a written report
- Two oil samples over a five-year period
- One intrusive maintenance visit (requiring a planned shutdown) to assess internal components
- Partial discharge monitoring
Priority
Includes everything in the Comprehensive package, plus:
- Yearly oil samples
- Generator support in the event our standby engineers are unable to restore supplies following an unplanned outage
Our HV maintenance customers have access to a 24/7, 365-day emergency call-out service. Our minimum response time is four hours, and the on-call engineer will always aim to attend sooner where possible.
If you are not an ESE maintenance customer, please call 105 and speak to your local Distribution Network Operator (DNO). Your call will be routed via the national 105 service (see our ‘What is 105?’ page).
Partial discharge monitoring provides early warning of insulation failure within high-voltage terminations. Using a handheld device, our engineers measure the decibel level at each termination, and if readings are above the acceptable threshold, we investigate further to confirm the condition of the insulation & recommend any remedial work.
Most high-voltage systems are serviced on an annual basis, with many checks completed with the equipment live, so site operations may continue. One visit in five should include a planned outage, so intrusive testing can be carried out on internal components.
Typical high-voltage equipment includes:
- Transformers
- High-voltage switchgear (including protection relays)
- Battery trip units
High-voltage maintenance covers visual inspections, testing and repairs of high-voltage electrical systems. Regular maintenance reduces the risk of equipment failure and unplanned outages and allows defects to be identified and resolved early. Using an authorised high-voltage contractor also helps you meet your duties under the Health and Safety at Work Act 1974 and the Electricity at Work Regulations 1989.