In short. Critical-power designs should be reviewed at defined stages by people who can challenge them, and accepted on evidence. A framework gives the questions, the documents and the tests for each stage, so gaps are found when they are cheap to fix and the handover proves the system works.
Stage gates
| Gate | Focus | Typical evidence |
|---|---|---|
| Requirements | What must be protected, for how long, against which failures | Load classification, outage tolerance, risk assessment |
| Concept design | Architecture and redundancy | Single-line, redundancy analysis, SPOF review |
| Detailed design | Ratings, protection, controls | Calculations, studies, FMEA, test plan |
| Procurement and FAT | Equipment fit and quality | Data sheets, factory test results |
| Installation and commissioning | Build quality, functional tests | Inspection records, test results |
| Integrated testing and handover | Whole-system performance | IST report, as-builts, training, O&M manuals |
Design review questions
- Which loads are critical and what are their tolerable outages?
- Which failures does the design survive, and which not?
- What are the single points of failure and shared dependencies?
- Do capacity, fault levels and protection hold in every configuration?
- Can any component be maintained while the load stays supplied?
- How does the system start, transfer, recover and black start?
- Are controls, DC and communication redundant where needed?
- How will it be tested and proven?
Acceptance criteria
Write them as measurable items before testing. Examples: transfer time below a set value, voltage within a band during transfers, battery autonomy at least a stated time at the site load, load-sharing within a tolerance, protection operates in a stated time. Agree who signs and what happens to non-conformances.
Finding and closing issues
- Log each finding with severity and owner.
- Decide fix, accept with reason or retest.
- Track to closure with evidence.
- Do not hand over with open critical findings.
Independent review
A reviewer who was not part of the design brings a fresh view. Use one for high-stakes systems, particularly for SPOF and common-cause issues, and for protection and control logic.
Handover package
- As-built drawings, including single-line, control and wiring.
- Calculations, study reports and settings.
- Test and commissioning records.
- Operating and emergency procedures.
- Maintenance plan and spares list.
- Training records.
Worked illustration
At the detailed-design gate, a reviewer finds that both ATS controllers take control power from one 24 V supply. This was invisible at concept level. Fixing it at that stage costs a drawing change; finding it at commissioning would cost rework and delay; finding it in an outage would cost the outage. The gate review exists to find items at the cheapest stage.
A design review in gates
| Gate | Questions |
|---|---|
| Requirements | Loads classified? Outage tolerance defined? Autonomy stated? |
| Concept | Architecture meets target? Single points identified? |
| Detailed design | Fault levels, coordination, earthing, controls, cooling checked? |
| Construction | Installed as designed? Independent routes actually separate? |
| Commissioning | Integrated tests passed? Failure scenarios proven? |
| Handover | Documents, training, spares, maintenance plan delivered? |
Checklist items that are often missed
- Fuel autonomy and delivery agreements.
- Cooling for the electrical rooms during generator operation.
- Black-start capability.
- Alarm routing and out-of-hours response.
- Capacity headroom for growth under failure conditions.
- Method-of-procedure documents for maintenance.
Independent review
A reviewer who did not design the system finds more issues. For high-criticality sites, appoint one at concept and again before handover.
Acceptance evidence
Require test records, calculation reports, as-built drawings and signed completion certificates. Acceptance is the moment to discover gaps, not the first emergency.
See integrated testing and FAT and SAT framework.
Common mistakes
- Skipping gates under schedule pressure.
- Acceptance criteria written after the test.
- Handover without as-built records.
What to send us
Send your design documents for review. Send your application details. See also integrated systems testing.
Questions engineers ask
When should a design be reviewed?
At each stage gate, with deeper reviews at concept and detailed design when changes are cheapest.
What are good acceptance criteria?
Measurable, agreed in advance and tied to the requirements.
Is an independent review necessary?
It is valuable for high-consequence systems because it challenges assumptions the design team may share.
What belongs in handover?
As-built records, studies, test results, procedures, maintenance plans and training.
This guide gives general principles. Apply your organisation’s design and quality procedures.