In short. Upgrading an operating site means changing the system while it keeps supplying the load. Success depends on knowing the as-found condition, planning in phases, providing temporary power, rehearsing each cutover and testing the result. The old system’s quirks are often the biggest risk.
Why brownfield is different
New builds start with a clean drawing. Existing sites have undocumented changes, mixed equipment ages, cables that are not where the drawing says, and loads that cannot be switched off. Every step must keep the load supplied or have an approved outage.
Phased approach
- Survey and verify: trace the real single-line diagram, test existing equipment, measure loads, check fault levels and protection settings.
- Define the target: the architecture, capacity and resilience goal.
- Plan the transition: phases, temporary supplies, outages and rollback.
- Build ahead of cutover: install new equipment alongside the old.
- Test before cutover: energise and test off-line.
- Cut over in small steps: with rehearsed procedures.
- Prove and decommission: test the new system, then remove the old.
Common modernisation scopes
| Scope | Typical issues |
|---|---|
| Generator replacement or addition | Space, foundations, fuel, exhaust, emissions, noise, paralleling with old units |
| UPS replacement | Load transfer without break, battery room, bypass arrangements |
| Switchgear replacement | Shutdown needs, temporary feeds, fault level changes |
| ATS and controls upgrade | Interface to old systems, logic migration |
| Adding redundancy or a second path | Cable routes, capacity, space |
See retrofit and modernisation matrix and upgrade and replacement planning.
Temporary power
Rental generators, temporary UPS or a mobile BESS can carry the load while equipment is changed. Plan connection points in advance, fuel, ventilation, earthing, protection and the transfer of controls. See rental and temporary power.
Risks to control
- Unknown wiring and unmarked circuits.
- Different generations of equipment that do not parallel cleanly.
- Higher fault levels from new sources exceeding old switchgear ratings.
- Control logic that nobody remembers.
- Shortened testing because of outage pressure.
Worked illustration
A hospital replaces an old 500 kVA generator with a new 750 kVA set. The survey finds that the old ATS, breakers and cables suit only 600 kVA. A rental generator is connected through a prepared point for the changeover. The ATS and cables are upgraded in a planned window. The new set is commissioned and load-tested off-line, then cut in with the rental set on standby. The load never loses power. The plan’s value was in survey and rehearsal, not in the equipment.
Handover
- Update drawings and records to as-built.
- Document settings and software.
- Train operators on the new system.
- Retest the integrated system.
Improving an operating critical system
A live facility cannot be shut down for an upgrade. Modernisation therefore proceeds in stages, each safe on its own, with tested rollbacks.
| Stage | Content |
|---|---|
| Assess | Drawings versus reality, capacity, condition, SPOF review |
| Define target | Required resilience, maintainability, growth |
| Plan staging | Which path or section is changed first; how load is kept up meanwhile |
| Temporary supply | Rental generator or UPS to carry load during cutovers |
| Execute with MOPs | Method-of-procedure documents, permits, spotters |
| Test and commission | Each stage proven before the next |
| Update records | Drawings, settings, labels, training |
Typical upgrade items
- Add a second source or path to remove a single point of failure.
- Replace obsolete protection or ATS controllers.
- Upgrade UPS to modular, or add BESS.
- Add monitoring and alarm management.
Constraints
Space, cable routes, existing earthing and fault levels often limit options. Surveys with thermal imaging and measurement find surprises early.
Risk windows
Schedule work at low-risk times and with the facility’s approval. Rental power can bridge; see rental power. See also upgrade and replacement planning.
Common mistakes
- Trusting old drawings.
- No rollback plan.
- Skipping a fault-level check when adding a source.
What to send us
Send existing drawings, photos and the target capacity. Send your application details. See also brownfield electrical study.
Questions engineers ask
Can we upgrade without shutting down?
Often yes with temporary power and phased cutover, but some steps usually need short, planned outages.
What is the biggest brownfield risk?
Unknown condition of the existing system. A proper survey reduces it.
Can new and old generators run together?
Often, but compatibility of controls, governors and alternators must be checked.
Do new sources affect old switchgear?
They can raise fault levels above old ratings, so check before adding sources.
This guide gives general principles. A site survey is required for specific recommendations.