What Tests Are Included in The Factory Acceptance Test Of Transformer

Factory Acceptance Test (FAT) is a critical quality verification process for transformers before they leave the factory, ensuring compliance with contracts, standards, and design requirements. The following are typical test project classifications and explanations:
1, Structural inspection
Appearance inspection
Check the shell, radiator, sleeve, etc. for damage, rust, and good sealing.
Nameplate and identification
Verify that the nameplate parameters (capacity, voltage level, connection group, etc.) are consistent with the contract.
Oil level and integrity of accessories
Confirm that the oil level is normal and that accessories such as pressure relief valves and gas relays are installed in place.
2, Electrical performance testing
Variable ratio test
Verify whether the voltage ratio error of each tap position meets the standard (such as ± 0.5%).
Measurement of DC resistance of winding
Check the balance of three-phase winding resistance (usually with a difference of ≤ 2%) to eliminate poor contact or disconnection.
Insulation resistance and polarization index
Measure the insulation resistance between windings and to ground (e.g. ≥ 1000M Ω) and the 10 minute/1-minute ratio (PI ≥ 1.5).
No load loss and current testing
Measure no-load loss and current at rated voltage to verify the iron core process and magnetic circuit design.
Load loss and short-circuit impedance testing
Measure load loss at rated current to verify winding design and manufacturing quality.
3, Insulation system test
External withstand voltage test (power frequency withstand voltage)
Apply high voltage (such as 70kV/1 minute for a 35kV transformer) to test the main insulation strength.
Induction voltage withstand test
High frequency voltage (such as twice the rated voltage) is used to assess the longitudinal insulation (inter turn, inter layer) without partial discharge or breakdown.
Partial discharge test (optional)
Monitor the discharge capacity (e.g. ≤ 500pC) and evaluate the purity of the insulation system.
4, Insulation oil test
breakdown voltage
New oil must be ≥ 60kV (IEC standard), and operating oil must be ≥ 50kV.
Dielectric loss factor (tan δ)
Detect oil aging (such as tan δ ≤ 0.5% at 90 ℃).
Moisture content and chromatographic analysis
Moisture content ≤ 20ppm, no abnormal increase in gas components (H ₂, CH ₄, etc.).
5, Protection and auxiliary system testing
Functional verification of protective devices
Calibration of alarm/trip action values for gas relays, pressure relief valves, and thermometers.
Cooling system test
Start the oil pump and fan, and check the automatic start stop function of the temperature control system.
Control circuit verification
The accuracy of analog signals (oil temperature, oil level) transmitted to the control cabinet.
6, Special test (as required by the contract)
Temperature rise test
Run at full load to thermal stability and verify that the top oil temperature rise (e.g. ≤ 55K) meets the standard.
Short circuit withstand capacity test
Simulate short-circuit current (type test) to assess mechanical and thermal stability.
Noise testing
The sound level under no-load conditions (such as ≤ 65dB (A)) meets environmental requirements.
7, Document and Record Review
Check factory documents: test reports, certificates of conformity, installation drawings, oiling reports, etc.
Confirm the transportation plan (collision recorder, nitrogen filling pressure, etc.).
8, Other projects
Phase and polarity verification: Ensure that the vector group (such as Dyn11) is correct.
Sealing test: Oil pump/valve leakage inspection.