In short. Resilience decays unless maintained. Batteries age, fuel degrades, settings drift, firmware changes, and loads grow. A lifecycle plan covers preventive and condition-based maintenance, spares, testing, ageing components and planned replacement, with a method for doing the work without losing protection.
Maintenance strategies
| Strategy | Description | Best for |
|---|---|---|
| Preventive | Scheduled tasks by time or running hours | Most equipment |
| Condition-based | Tasks when measurements show need | Batteries, transformers, bearings |
| Predictive | Trends forecast failures | Where data is rich |
| Corrective | Repair after failure | Non-critical items only |
Key tasks by equipment
- Generators: oil, coolant and filter changes, fuel quality checks, starting batteries, load tests, control and alarm tests. See preventive maintenance.
- ATS and switchgear: contact inspection, operating tests, protection relay testing, thermography.
- UPS and batteries: capacity and impedance checks, firmware, capacitor and fan replacement.
- Distribution: torque checks, thermographic surveys, cleaning, breaker exercise.
- Controls and DC: battery tests, alarm tests, backup of settings and logic.
Lifecycle and ageing
Different components age at different rates. Plan replacement by the weakest-life items: batteries often the first, then fans and capacitors, then controls and software, then switchgear. Track end-of-support dates for control and protection hardware and software, because unsupported parts are a long-term risk.
Spares
- Hold critical spares on site where lead times are long.
- Check spares are compatible with current firmware and hardware revisions.
- Rotate and test spares like installed equipment.
Maintaining without losing protection
- Work path by path, never both at once.
- Verify the remaining path before starting.
- Use a method of procedure with abort steps.
- Restore protection and controls to auto and test afterwards.
- Record work and results.
See concurrent maintainability.
Settings and configuration control
Back up relay settings, controller configurations and PLC logic. Control changes through a documented process. Many outages after maintenance come from a setting left changed or a controller left in manual.
Worked illustration
A site’s UPS batteries are five years old and pass the monthly voltage check. A capacity test, however, shows 70 per cent of rated capacity, below the design margin. Without the test they would have failed during the next outage. A condition-based programme replaces them on measured health, not the calendar. The same site checks that fuel samples are within specification and that spare filters are on site, reducing the weak points a real outage would find.
Resilience decays without maintenance
Batteries age, fuel degrades, breakers stick, filters clog and settings drift. A system that was resilient at commissioning loses that resilience quietly.
| Item | Typical interval (confirm with maker) |
|---|---|
| Generator on-load run | Monthly, at least 30 to 60 minutes |
| Generator service | Per hours and annual schedule |
| Fuel sampling and polishing | Every 6 to 12 months |
| UPS battery test | Annually, with discharge test as needed |
| UPS battery replacement | Typically 4 to 10 years depending on type and temperature |
| ATS and breaker exercise | Annually |
| Thermography | Annually |
| Protection relay test | Every 2 to 5 years |
Lifecycle planning
- Record installation dates and expected lives.
- Plan replacements before end of life, not after failure.
- Keep critical spares: starter motor, filters, controller card, battery module.
- Track obsolescence and support dates.
Maintenance without risk
Use concurrent maintainability: work on one path while the other carries the load, with written procedures, a second-person check and a defined rollback.
Contracts
An annual maintenance contract with response times, spares and emergency support gives predictable cover. See AMC and preventive maintenance.
Common mistakes
- Time-based replacement only, without measuring condition.
- No records of settings.
- Maintenance that leaves the system in manual or bypass.
- Obsolete controls with no support.
What to send us
Send equipment lists, ages and current maintenance records. Send your application details. See also annual maintenance contracts.
Questions engineers ask
How often should a standby generator be serviced?
Follow the manufacturer’s schedule and your running hours, with more frequent checks of starting, fuel and controls.
Why are batteries so important?
They are often the first thing to fail and are critical to starting and bridging. Measure their health, not just voltage.
What is condition-based maintenance?
Doing tasks when measurements show a need, not only at fixed intervals.
How do I avoid maintenance-caused outages?
Use method statements, work one path at a time and restore and test the system after each task.
This guide gives general principles. Follow manufacturers’ instructions and site safety rules.