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Routine and Design tests on power
transformers as required by IEEE
C57.12.00 and C57.12.90
C57.12.00 IEEE Standard for General Requirements
for Liquid-Immersed Distribution, Power and
Regulating Transformers
Service Conditions
Rating Data
Construction
Short Circuit
Testing and Calculations
Tolerances
Connections for shipment
Annex for Front of Wave (Informative)
C57.12.90 IEEE Standard Test Code for LiquidImmersed Distribution, Power and Regulating
Transformers
Resistance Measurements
Ratio tests
Load Loss and impedance
Temperature rise tests
Audible sound level
Annex A Partial Discharge
Polarity and Phase relation
No-load loss and excitation
Di-electric tests
Short circuit tests
Calculated Data
Annex B Frequency conversion
Routine and Design tests
• Routine tests shall be made on every transformer
to verify that the product meets the design
specifications.
• Design tests shall be made on a transformer of
new design to determine the adequacy of the
design of a particular type, style or model of
transformer or its component parts.
• Other tests are identified in individual product
standards and may be specified by the purchaser
in addition to routine tests.
Insulation levels
• Class I power transformers shall include power
transformers with high-voltage windings of
69kV and below.
• Class II power transformers shall include
power transformers with high-voltage
windings from 115kV thru 765kV.
Routine, design and other tests for transformers
Tests
Type
Resistance measurements of all windings on the rated
voltage tap and at the tap extremes
Routine
Explanation of the test
To verify that the measured winding
resistance is within 3% of the calculated
winding resistance, and that all internal
connections and welds were performed
properly
Winding Insulation Resistance
Routine for Class-II To measure the quality and dryness of the
, Other for Class-I transformer insulation system
Core Insulation Resistance
Routine for Class-II To verify that no unintentional grounds are
, Other for Class-I present on the transformer core
Ratio, polarity and phase relation tests on the rated
voltage connection and on all tap connections
Insulation Power Factor and capacitance
Control (auxiliary) cooling losses
Low frequency test on auxiliary devices and current
transformers
Single Phase Excitation tests on the rated voltage
connection.
Routine
To verify that all windings have the correct
number of turns and all winding leads are
properly connected and the correct phase
rotation is achieved.
To verify the quality of the transformer
Routine for Class-II
insulation system.
, Other for Class-I
Other
To measure the losses drawn by the fans and
other auxiliary devices during operation
Other for Class I, To verify the dielectric integrity of the
Routine for Class II auxiliary devices, wiring and CTs
Other
To verify that the core design and its
performance is satisfactory, and that no
failures are located in the winding insulation
system
Routine, design and other tests for transformers
Tests
No-Load Losses and exciting current at 100% and
110% of rated voltage and at rated power frequency
and on the rated voltage tap connections
Impedance voltage and load loss at rated current and
rated frequency on the rated voltage connection and at
the tap extremes.
Zero Phase Sequence impedance voltage
Temperature Rise Test
-At minimum and maximum ratings of the first unit of
a new design
- At minimum and maximum ratings when
temperature rise tests are specified.
- Special ratings per customer specs
Low frequency di-electric test
(Applied Potential test)
Type
Explanation of the test
Routine
To verify that the core was designed and
manufactured to meet the
calculated/guaranteed core loss value
Routine
To verify that the windings and active part
were designed and manufactured to meet
the calculated/guaranteed load loss and
percent impedance values
Design for
Class I,
Routine for
Class II
To verify that the active parts with
windings were designed and manufactured
to the calculated/guaranteed zero phase
sequence impedance value
Design
Other-Other
Other-Other
Routine
The Temperature Rise Test verifies that the
thermal performance of the transformer
cooling system is designed and
manufactured to meet the calculated and
guaranteed values
To verify that the insulation between the
windings and the windings to ground is
adequate, including lead clearances
Routine, design and other tests for transformers
Tests
Lighting Impulse Test
Switching impulse, phase-to-ground
Partial Discharge and Radio Interference
test
Audible Sound Level Test
Dissolved gases in oil analysis
CT Ratio and Polarity
Type
Explanation of the test
Design& Other for Class I,
Routine for Class II
Other for both but Routine for
345kV and above
To verify the insulation class to withstand the
guaranteed basic insulation level (BIL)
To verify the insulation integrity of the
transformer for switching stress in the field.
To verify the integrity of the transformer
insulation system to meet the guaranteed level
of apparent charges occur within the
transformer.
Routine for Class-II
Other for Class-I
Design for first unit and other
Routine for Class-II
Other for Class-I
Routine
CT Insulation Resistance
Routine
Operational test of all devices
Routine
Single phase impedance test
Other
Sweep Frequency response Analysis test
Other
To verify that the sound generated by the
transformer does not exceed the guaranteed
maximum decibel level during operation.
To verify that the transformer had no
combustible gas generation during various
types of tests
To verify that all current transformers are
connected and polarity is correct
To verify that all the secondary leads of the
current transformers have adequate insulation
to ground all the way to the control cabinet
To verify all the control wiring is correct and
the auxiliary devices are operational.
To measure the impedance value of each set
of windings separately
To measure the response of each phase under
different frequencies. This test is to verify any
coil movement between different times of
testing.