A factory acceptance test (FAT) is a contractual verification stage before shipment. It is not, by itself, a separate IEC test category. A FAT may combine document review, visual inspection, agreed electrical tests, witness points and closure of outstanding items for the serial-numbered transformer.
1. Separate the test categories
| Term | Purpose | Boundary |
|---|---|---|
| FAT | Project acceptance event covering the agreed factory checks and records. | Content depends on the contract and approved ITP. |
| Routine test | Test category normally applied to each transformer under the governing product standard. | The exact list depends on transformer type, rating and standard. |
| Type test | Demonstrates specified performance of a representative design. | A prior report may not represent the exact serial-numbered unit. |
| Special test | Addresses a purchaser requirement or particular design concern. | May add cost, time or external laboratory requirements. |
2. Freeze the governing basis
Before testing, align the purchase order, project specification, approved datasheet, standard and edition, drawings, serial number, ITP, acceptance tolerances and report language. If the project specification modifies a standard requirement, record the modification explicitly.
3. Typical electrical checks
The following checks are commonly encountered, but they are not a universal mandatory list.
Winding resistance
Review the winding and tap tested, phase values, measured temperature, correction basis and phase consistency. A resistance value without temperature information may be difficult to interpret.
Voltage ratio, polarity and vector group
Confirm required tap positions, terminal designations and the actual vector group. The report should state the result rather than only showing “pass”.
No-load loss and current
Review applied voltage, frequency, measured loss/current, correction method where applicable, guaranteed limit and tolerance basis. No-load loss persists while the transformer is energized.
Load loss and short-circuit impedance
Check test current and frequency, measured temperature, reference-temperature correction, corrected load loss, impedance base and guaranteed limits. Compare offers and test results only on a consistent basis.
Dielectric tests
The programme depends on voltage class, winding category, transformer type and governing standard. The approved procedure should state the test voltage, duration, terminal arrangement and acceptance criterion. Do not copy dielectric levels from another project.
Functional checks
Depending on configuration, verify tap indication, temperature devices, cooling control, pressure/oil-level or gas devices, marshalling wiring, alarms, trips and communication interfaces against the approved schematic.
4. Review type and special-test evidence
When a historical report is offered, compare manufacturer and manufacturing site, transformer construction, rating, voltage class, winding/core/tank design, cooling, impedance, insulation level, standard edition and report issuer. Evidence for a different design family should not be represented as the report for the purchased unit.
| Topic | Review focus |
|---|---|
| Short-circuit withstand | Evidence route and design similarity under IEC 60076-5 or the project-specified basis. |
| Temperature rise | Ambient, cooling state, losses used, sensor locations and tested construction. |
| Sound level | Factory sound-power requirement versus any separate on-site sound-pressure limit. |
| Partial discharge | Applicability, circuit, background noise, voltage sequence and acceptance criterion. |
| Impulse/dielectric | Insulation level, winding category, waveform and required standard. |
5. Inspect the supplied configuration
An effective FAT also verifies identity, construction and documentation.
6. Use a controlled FAT workflow
Freeze drawings, approve the ITP, assign hold/witness points, review type-test evidence and issue a checklist.
Confirm identity and revisions, record instruments and conditions, witness the approved sequence and capture numerical results.
Issue signed reports, close deviations, update as-built drawings and release shipment through the agreed quality process.
7. Read the final report critically
For every result, ask: what was tested; under what voltage, current, frequency and temperature; how it was corrected; what acceptance limit applied; and who reviewed it. A complete result normally identifies the procedure, instrument, conditions, raw/corrected value where relevant, limit, conclusion and signatures required by the ITP.
Resolve these red flags before shipment
- Serial number differs between nameplate, report and packing list.
- Vector group or terminal labels conflict with approved drawings.
- Loss result lacks a reference-temperature basis.
- Impedance uses a different kVA base from the guaranteed value.
- The report says only “pass” where numerical results are required.
- A type-test report is supplied without an applicability assessment.
- Accessories differ from the approved bill of materials.
- Open punch items or as-built changes are undocumented.
Suggested specification wording
The project engineer and contract team should adapt this wording to the exact transformer and destination requirements.