In short. Start from the symptom, not the study name. Each electrical problem points to one or two studies that answer it. This guide maps common problems on generator and power systems to the right study, the question it answers and the data to prepare.
Problem to study
| Problem | Study | Question it answers |
|---|---|---|
| Generator stalls or dips on a motor start | Motor starting | Can the source start the motor and hold voltage? |
| Breaker too small or too slow | Short-circuit and TCC coordination | Is equipment rated and does the right device trip first? |
| Wrong generator size | Generator sizing | Does it carry load, motor start and steps? |
| Voltage low at far end | Cable and voltage drop, load flow | Where does voltage fall and why? |
| Overheating, UPS or drive faults on generator | Harmonic study | Is distortion within limits on generator supply? |
| Low power factor or capacitor trouble | Reactive power | How much correction and is it safe on generator? |
| Shock risk, relay misoperation | Earthing study | Do earth faults clear safely? |
| Worker safety at switchgear | Arc-flash study | What energy could a worker receive? |
| Transformer start trips the set | Inrush study | Can we energise without tripping? |
| Need for no outage or N+1 | Reliability study | What architecture meets the target? |
| Paralleling or utility interconnection | Synchronising, interconnection | Safe, approved parallel operation? |
| Adding load or sources later | Expansion study | What headroom do we need? |
| Old, undocumented site | Brownfield study | What is really there? |
Choosing the order
- Verify the as-built system and loads.
- Run load flow and short-circuit as the foundation.
- Run the studies that use those results: coordination, arc flash, motor starting, harmonics.
- Run architecture studies: reliability, expansion, interconnection.
- Validate inputs and document assumptions. See inputs and validation.
How to prepare
- A single-line diagram, even if hand drawn.
- A load list with motor sizes and starting methods.
- Generator, transformer and UPS nameplates.
- Incident descriptions with dates and what was running.
- Any measurement data or logs.
Illustrative example
A plant reports that its new generator trips when the cooling tower motor starts, and the UPS alarms after transfer. The mapping suggests a motor starting study for the first symptom and a harmonic study for the second. The foundation work is a load list and the generator datasheet, and the coordination study follows once the cases pass.
From the problem you see to the study you need
| Problem or question | Study required |
|---|---|
| How large a generator do we need? | Load list and demand, generator sizing and transient performance |
| Lights flicker or motors stall on generator | Motor starting and voltage dip, load-step and frequency response |
| Breaker rating questions after adding a source | Short-circuit study, maximum and minimum |
| Unexpected trips or no trip on a fault | Protection coordination, TCC |
| Safety of maintenance work on live boards | Arc-flash study |
| Overheating, nuisance trips, capacitor failures | Harmonic and resonance study |
| Low power factor or generator unstable on capacitors | Reactive power and power factor study |
| Voltage drop at far loads | Load flow, cable sizing |
| Shock complaints, equipment damage in storms | Earthing, GPR, lightning and surge risk |
| Plan to parallel with the grid | Utility-DG interconnection |
| Need to prove uptime | Reliability, FMEA, redundancy study |
| Old plant, drawings unreliable | Brownfield study |
| Facility expansion planned | Capacity expansion study |
How to start
- State the question in one sentence.
- Choose the study from the table.
- Collect the data it needs.
- Agree acceptance criteria before running.
Often several studies are needed in sequence. See study inputs and validation.
For help scoping a study, use the application engineering enquiry.
Common mistakes
- Ordering a study by name rather than by problem.
- Skipping the foundation studies.
- Starting with no data.
What to send us
Describe the symptom and send what you have. Send your application details.
Questions engineers ask
Do I need every study?
No. Choose by the problem and the risk.
Which study first?
Usually load flow and short-circuit, since others depend on them.
Can one study answer several problems?
Sometimes. For example, a good short-circuit study supports coordination and arc flash.
How do I know if the result is reliable?
Check the inputs, assumptions and sensitivity, and have it reviewed.
This guide gives general principles. Study scope should be agreed with a qualified engineer.