Functional testing is unreliable when the design baseline is moving. A pre-FAT configuration review ensures that drawings, installed components, relay files and customer comments describe the same deliverable.
Learning objectives
Establish the test baseline, identify unresolved deviations and prevent results from being invalidated by late configuration changes.
Core engineering principles
The approved drawing revision controls wiring
Testers should not use an obsolete print or an unapproved marked-up copy without controlled disposition.
Installed hardware must match BOM and evidence
Ratings, model codes, firmware and accessories are verified before test scripts assume capabilities.
Relay and network files are configuration items
Native setting files, logic, CID/SCD and switch configurations require version identification.
Customer comments need closure status
Open comments can be accepted, rejected or pending with owner and impact. They must not remain hidden in email.
Late changes require regression scope
A modified output or interlock can affect tests already completed. The change record should identify which tests are repeated.
Engineering application method
- Step 1: Freeze approved drawing and BOM revisions.
- Step 2: Capture device, firmware and configuration versions.
- Step 3: Review comment and deviation registers.
- Step 4: Verify test scripts against the baseline.
- Step 5: Control any FAT change and repeat affected tests.
Practical example
Changing one relay binary output after its functional test also affects terminal wiring, trip matrix and SCADA indication. Regression testing must cover the full chain.
Common mistakes
- Testing from printed uncontrolled drawings.
- Recording only relay PDF settings.
- Changing firmware during FAT silently.
- Closing comments without evidence.
- Retesting only the edited screen.
Design and review checklist
- Is one baseline revision declared?
- Do installed models match BOM?
- Are native files archived?
- Are comments dispositioned?
- Is regression testing defined for changes?
Standards basis and official sources
- IEC 62271-200:2021 + AMD1:2024 — AC metal-enclosed switchgear assemblies above 1 kV and up to 52 kV.
- IEC 60255-1:2022 — Common requirements for measuring relays and protection equipment.
- IEC 61850-10:2012 + AMD1:2025 — Conformance testing within the IEC 61850 series.
Engineering note: Verify the contracted standard edition, amendments, manufacturer evidence and project-specific studies before applying these principles to a supplied assembly.