Tests for liquid immersed transformers

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_m(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

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

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

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.