Tests for liquid immersed transformers

Testing room

 

All transformers are tested in compliance with IEC 60076-1


Routine tests

Below the list of routine tests to be performed on liquid immersed 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
  • Leak testing with pressure (tightness test)
  • Tightness tests and pressure tests for tanks for gas-filled transformers
  • Check of the ratio and polarity of built-in transformers
  • Check of core and frame insulation for liquid immersed transformers with core or frame insulation

​Additional routine tests for transformers with U>75 kV

  • Determination of capacitances windings-to-earth and between windings
  • Measurement of DC insulation resistance between each winding to earth and between windings
  • Measurement of dissipation factor (tan δ) of the insulation system capacitances
  • Measurement of dissolved gases in dielectric liquid from each separate oil compartment except diverter switch compartment
  • Measurement of no-load loss and current at 90% and 110% of rated voltage

Type tests

Below the list of type tests that can be performed on liquid immersed 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 and liquid pump motors
  • 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 liquid Iimmersed ransformers 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 DC insulation resistance between each winding to earth and between windings
  • Vacuum deflection test on liquid immersed transformers
  • Pressure deflection test on liquid immersed transformers
  • Vacuum tightness test on site on liquid immersed transformers
  • 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)
  • Measurement of dissolved gasses in dielectric liquid
  • Mechanical test or assessment of tank for suitability for transport (to customer specification)
  • 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 current test
  • Measurement of the transmitted vibrations
  • Test on vibration floor (seismic)

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

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.