Tests for dry type transformers

Testing room


All transformers are tested in compliance with IEC 60076-1 and IEC 60076-11

Routine tests

Below the list of routine tests to be performed on dry-type transformers:

  • Measurement of winding resistance
  • Measurement of voltage ratio
  • Checking of phase displacement
  • Measurement of short-circuit impedance and load loss
  • Measurement of no-load loss and current
  • Dielectric routine tests (please check below according to the U(IEC 60076-3))
  • Insulation test and functional verification of accessories
  • Tests on on-load tap changers, where appropriate
  • Auxiliary wiring insulation test
  • Check of the ratio and polarity of built-in transformers
  • Measurement of partial discharges

Type tests

Below the list of type tests that can be performed on dry-type transformers:

  • Temperature-rise type test (IEC 60076-2)
  • Dielectric type tests (IEC 60076-3)
  • Determination of sound level (IEC 60076-10) for each method of cooling for which a guaranteed sound level is specified
  • Measurement of the power taken by the fan
  • Measurement of no-load loss and current at 90% and 110% of rated voltage

Special tests

Below the list of special tests that can be performed on dry type transformers directly in SEA or in our associated laboratories:

  • Dielectric special tests (IEC 60076-3)
  • Winding hot-spot temperature-rise measurements
  • Determination of capacitances windings-to-earth and between windings
  • Measurement of dissipation factor (tan δ) of the insulation system capacitances
  • Determination of transient voltage transfer characteristics
  • Measurement of zero-sequence impedance(s) on three phase transformers
  • Short-circuit withstand test
  • Measurement of d.c. insulation resistance between each winding to earth and between windings
  • Measurement of frequency response (Frequency Response Analysis or FRA); the test procedure shall be agreed between manufacturer and purchaser
  • Check of external coating (ISO 2178 and ISO 2409 or as specified)
  • Determination of weight with transformer arranged for transport for transformers up to 1,6 MVA by measurement; for larger transformers by measurement or calculation as agreed between manufacturer and purchaser
  • Detection of harmonic content in no load current
  • Thermographic detection of hot-spots
  • Measurement of winding inductance
  • Recurrent voltage surges test
  • In-rush surges test
  • Verification of the environmental classes
  • Verification of the climatic classes
  • Verification of the behaviour to fire classes
  • Low temperature test
  • Measurement of the transmitted vibrations
  • Test on vibration floor (seismic)

The type and/or special tests that can be carried out on the transformers are always listed separately both in phase of offer and/or order.

Other tests requirements for specific transformers are specified in IEC 60076-3

Archive of type tests

SEA has a large archive of type and special tests carried out on many dry-type transformers that can be consulted by its customers.
Some examples of test performed on cast resin transformers:

  • Toxicity tests by Breda Scientific Institute
    In compliance with the test methods provided by CEI 20-37 on a cast resin sample, a toxicity percentage lower than 0.1% has been recorded for gases released during combustion.

  • Fire behaviour test performed by CESI
    This test has been carried out on a sample composed by a complete leg (core, LV and HV windings) of a 1600 kVA transformers.

  • Various tests on insulating materials
    Samples made of the same used resin for the autoestinguishing test have been analized by IMQ.  

  • Low temperature tests
    Thermal cycle test has been carried out and passed at CESI (4 cycles from -20 °C to +20 °C in 24 hours).
    Thermal shock test at -50 °C has been carried out and passed at Magrini's lab.

  • Dynamic short circuit withstand test
    Several certificates of dynamic short circuit tests carried out on transformers with different powers and voltages have been performed at CESI.