In short. In an existing site the drawings are usually wrong somewhere. A brownfield study starts by finding out what is really installed, how it behaves and what condition it is in. Only then can new generators, ATS or loads be added without surprises.
Study stages
- Collect records. Drawings, load lists, settings, test reports, maintenance history, incident logs.
- Site survey. Walk the system. Photograph nameplates, labels, wiring and busbars. Compare with drawings and mark differences.
- Measure. Load profile, power quality, phase balance, voltage, temperature. See load study.
- Verify ratings. Breaker, busbar and cable ratings against fault levels, including any new source.
- Condition assessment. Insulation, contacts, thermal scans, relay testing, battery health.
- Gap analysis. Against standards, safety rules and the target requirement.
- Risk register. Rank issues by consequence and likelihood.
- Staged plan. Order work to keep supply, with outage windows defined.
What commonly turns up
| Finding | Why it matters |
|---|---|
| Undocumented loads and tappings | Capacity and protection assumptions fail |
| Fault level above equipment rating | Safety risk and need for upgrade |
| Old protection with no testing | May not operate |
| Poor earthing and bonding | Shock risk, relay malfunction |
| Overloaded neutral or harmonics | Heating and trips |
Working live
Treat any work on live or recently live equipment under permit-to-work and lock-out procedures. Plan temporary supply where a shutdown is not acceptable. See rental power and upgrade and replacement planning.
Deliverables
- As-found single-line diagram. See single-line diagram engineering.
- Updated load list and demand summary.
- Rating and fault-level check table.
- Risk register with actions.
- Staged implementation plan.
Illustrative example
A factory wants to add a second generator. The survey finds that the main busbar rating is lower than assumed, two feeders are not on the drawing and the main breaker has not been tested for years. The study updates the diagram, tests the breaker, limits the added fault contribution and phases the work over two weekends.
Why brownfield is harder than new design
In an existing plant the drawings are often out of date, the equipment is old, and the system cannot be shut down at will. The study begins with verification, not calculation.
Assessment steps
- Walk down: trace the real network and compare with drawings.
- Collect nameplates: transformers, breakers, relays, generators, motors, cables.
- Log loads: record at least a representative week of demand with a power analyser.
- Review protection: relay types, settings, last test dates.
- Inspect condition: thermography, insulation tests, breaker operation.
- Build the model: with unverified items flagged.
- Study: fault level, capacity, coordination, generator suitability.
| Typical finding | Typical consequence |
|---|---|
| Fault level above breaker rating after upgrades | Replace or add current limiting |
| Missing or incorrect settings | Review and reset |
| Unlabelled or undocumented circuits | Trace, tag and update drawings |
| Overloaded transformer or cable | Redistribute or upgrade |
| Obsolete protection | Plan retrofit |
Working live safely
Many checks need the plant running. Use non-intrusive tools and follow site electrical safety rules. Where an outage is unavoidable, bring a temporary generator to protect critical loads.
See legacy modernisation and study inputs and validation.
Common mistakes
- Trusting old drawings.
- Designing before measuring.
- Planning outages after the design is fixed.
What to send us
Send what records you have. Send your application details.
Questions engineers ask
Why survey if we have drawings?
Drawings drift from reality. A survey finds the differences.
How long should measurement run?
Long enough to capture typical and peak operation, often one to several weeks.
Can we upgrade without a shutdown?
Often with temporary supply and good planning, though some tie-ins need short outages.
What if equipment is obsolete?
Plan replacement or support spares, and reflect that in the risk register.
This guide gives general principles. Work must follow site safety rules and regulation.