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Request a Quote — FAT Included on Request
Include your test requirements in the RFQ. We confirm which routine and type tests are available, and coordinate third-party inspection if required.
Quality Assurance Guide
Transformer Factory Acceptance Test (FAT) Checklist
A factory acceptance test is a witnessed routine test at the manufacturer's facility before shipment. Buyers who insist on FAT catch non-conformances before the transformer reaches site — where corrections are far more costly and time-consuming.
FAT, Routine Test, and Type Test — What Is the Difference?
These three terms are often confused. Understanding the distinction helps you specify what you need in your purchase order.
| Test category | Performed on | Purpose | Buyer present? |
|---|---|---|---|
| Routine test | Every unit produced | Verify the individual transformer meets rated parameters | No — internal quality control |
| Type test | One unit per design | Prove the design meets standard under extreme conditions (temperature rise, impulse, short-circuit) | Optional — done once per design family |
| FAT | Every unit (when specified) | Witnessed routine test: buyer or inspector verifies results before shipment | Yes — this is the definition of FAT |
1 Visual Inspection
- Tank condition — no dents, weld seams intact, no visible oil seepage
- Bushing condition — no cracks, chips, or contamination on HV and LV bushings
- Nameplate securely attached and legible — correct serial number
- Oil level gauge visible and reading within normal range
- Conservator tank fitted and oil level showing correctly (for oil-immersed units)
- Radiators / cooling fins: no damaged fins, all valves in correct position
- Paint finish — consistent, no bare metal spots, correct colour per order
- Bolted fittings tight — no loose flanges, plugs, or cover plates
- Buchholz relay fitted (where specified) and correctly connected
- Temperature indicators (WTI / OTI) fitted, sensors connected, pointer zeroed
- Pressure relief valve fitted (where specified)
- Earthing terminals present and accessible
- Lifting lugs and jacking pads — undamaged
2 Nameplate Verification
Cross-check the nameplate data against your purchase order line by line:
- Rated capacity (kVA or MVA) matches order
- HV and LV rated voltages correct
- Frequency (50 Hz or 60 Hz) correct
- Vector group matches specification (e.g. Dyn11)
- Impedance voltage % matches specification
- Cooling designation (ONAN / ONAF / AN / AF) correct
- Standard reference (IEC 60076 / ANSI / GB/T) correct
- Serial number unique and recorded for traceability
- Year and month of manufacture recorded
- Manufacturer name and country of origin correct
- Mass (total / oil / active part) plausible for the rating
3 Electrical Routine Tests
Winding Resistance Measurement
DC resistance of each winding measured at each tap position. Used to verify conductor continuity and detect shorted or open turns. Results corrected to reference temperature (75°C per IEC, 85°C per ANSI). Values should be balanced between phases (typically within ±0.5%).
Turns Ratio Test
Actual voltage ratio measured and compared to nameplate ratio at each tap. The measured ratio should agree with the specified turns ratio to within ±0.5% (IEC) at each tap position. Verifies that the tap changer is correctly connected and the turns count is correct.
Vector Group / Phase Displacement Verification
Confirms that the relative phase angle between HV and LV windings matches the declared vector group (e.g. Dyn11 = 30° displacement). Critical for parallel operation and protection relay coordination.
Short-Circuit Impedance and Load Loss (Pk)
The short-circuit (load) loss and leakage impedance measured at rated current, corrected to reference temperature. Load loss (Pk) determines the transformer's copper loss at full load — confirm it does not exceed the guaranteed value in your specification. Impedance % affects fault current levels.
No-Load Loss (P0) and No-Load Current
Core loss measured at rated voltage and frequency, with no load connected. No-load loss is present 24/7 whenever the transformer is energised. Verify that P0 does not exceed the guaranteed value. No-load current (excitation current) should also be within specified limits. These values can be entered directly into the Loss Calculator.
Insulation Resistance (IR) and Polarisation Index (PI)
Megohm test applied between each winding and earth (and between windings). Higher resistance is better. The polarisation index (PI = IR at 10 min / IR at 1 min) indicates insulation condition — a PI below 1.0 on a new transformer is cause for concern. Minimum acceptable values depend on voltage class.
Applied Voltage (Power Frequency Withstand)
Elevated AC voltage applied between each winding and earthed tank for 60 seconds. The test voltage level is defined by the voltage class and insulation level in the standard. No breakdown or flashover is acceptable.
Induced Overvoltage
The LV winding is energised at double rated voltage (using twice the rated frequency to avoid core saturation). Verifies the inter-winding and inter-turn insulation can withstand temporary overvoltages.
Oil Dielectric Strength (for Oil-Immersed Units)
Oil sample taken from the transformer and tested for breakdown voltage (BDV). IEC 60156 specifies the test procedure. BDV should be ≥60 kV (IEC, for 170 kV class and below at 2.5 mm gap). Lower values indicate moisture or contamination in the oil.
Dissolved Gas Analysis (DGA) — If Requested
Gas-in-oil analysis detects combustible gases (H₂, CH₄, C₂H₂, CO, etc.) that are produced by thermal and electrical faults inside the transformer. A baseline DGA on new oil before shipment is useful for comparison during service life. Not a routine test — request it specifically.
4 Documents to Collect After FAT
Before approving shipment, confirm you have received — or will receive with the shipment — the following:
- Routine test report — Signed by the manufacturer's test engineer, listing all measured values against specified limits.
- Routine test certificate — Formal certificate confirming the unit has passed all routine tests per the applicable standard.
- DGA report — Dissolved gas analysis on the insulating oil (if requested as a contract requirement).
- Dimensioned outline drawing — Overall dimensions, terminal connection diagram, weight, and centre-of-gravity data — needed for installation planning.
- Packing list — Item counts, crate dimensions, gross and net weights — required for freight and customs documentation.
- Nameplate photo — High-resolution photograph of the nameplate as installed — useful for records and spare-part ordering.
- Third-party inspection report — If SGS / BV / Intertek witnessed the test, their signed report constitutes independent certification.
Third-Party Inspection Agencies
If you cannot send your own engineer to China for the FAT, a third-party inspection agency can attend on your behalf. The three most widely used for transformer FAT in China are:
SGS
Global testing and inspection group. Can arrange inspectors at transformer factories throughout China. Provides independent test witnessing reports accepted by most utility and EPC clients.
Bureau Veritas (BV)
International classification and testing body. BV inspection reports are widely recognised by African, Middle East, and European utilities. BV China offices cover major manufacturing cities.
Intertek (ETL)
Global quality and safety testing organisation. Widely used by North American buyers sourcing from China. Can also issue ETL marks for ANSI-market transformers where required.
To arrange third-party inspection: contact the agency directly with the factory location and test date. Alternatively, ask the transformer manufacturer — most established factories are accustomed to hosting SGS, BV, or Intertek inspectors and can coordinate the schedule.
Use FAT Results in the Loss Calculator
The no-load loss (P0) and load loss (Pk) values from the routine test report are the most accurate inputs for energy cost modelling. Enter them directly into the Transformer Loss Calculator to compare the actual tested unit against your specification guarantee or a competing offer.
Open Loss CalculatorRequest a FAT-Supported Quote
XinHuan supports factory acceptance testing for all orders. Tell us your test requirements in the RFQ.
Request a Quote Ask About FAT ArrangementsFAT Quick Reference
- Visual inspection passed
- Nameplate matches PO
- Winding resistance (all taps)
- Turns ratio (all taps)
- Vector group confirmed
- Load loss Pk ≤ guaranteed
- No-load loss P0 ≤ guaranteed
- Impedance % within tolerance
- Insulation resistance (HV/LV/E)
- Applied voltage — no breakdown
- Induced voltage — no breakdown
- Oil BDV ≥ 60 kV (if oil unit)
- Test report signed
- DGA baseline (if required)
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