IEEE Jackson PES Meeting

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 DataConstruction Short CircuitTesting and Calculations TolerancesConnections for shipmentAnnex for Front of Wave (Informative)

C57.12.90 IEEE Standard Test Code for Liquid-Immersed Distribution, Power and Regulating Transformers

Resistance Measurements Polarity and Phase relation Ratio tests No-load loss and excitationLoad Loss and impedance Di-electric testsTemperature rise tests Short circuit testsAudible sound level Calculated DataAnnex A Partial Discharge 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 transformersTests Type Explanation of the test

Resistance measurements of all windings on the rated voltage tap and at the tap extremes Routine

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 , Other for Class-I

To measure the quality and dryness of the transformer insulation system

Core Insulation Resistance Routine for Class-II , Other for Class-I

To verify that no unintentional grounds are present on the transformer core

Ratio, polarity and phase relation tests on the rated voltage connection and on all tap connections 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.

Insulation Power Factor and capacitance Routine for Class-II , Other for Class-I

To verify the quality of the transformer insulation system.  

Control (auxiliary) cooling losses Other To measure the losses drawn by the fans and other auxiliary devices during operation

Low frequency test on auxiliary devices and current transformers

Other for Class I, Routine for Class II

To verify the dielectric integrity of the auxiliary devices, wiring and CTs

Single Phase Excitation tests on the rated voltage connection. 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 transformersTests Type Explanation of the test

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

Routine To verify that the core was designed and manufactured to meet the calculated/guaranteed core loss value

Impedance voltage and load loss at rated current and rated frequency on the rated voltage connection and at the tap extremes.

Routine

To verify that the windings and active part were designed and manufactured to meet the calculated/guaranteed load loss and percent impedance values

Zero Phase Sequence impedance voltage

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

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

Design

Other-Other

Other-Other

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

Low frequency di-electric test(Applied Potential test) Routine

To verify that the insulation between the windings and the windings to ground is adequate, including lead clearances

Routine, design and other tests for transformersTests Type Explanation of the test

Lighting Impulse Test Design& Other for Class I, Routine for Class II

To verify the insulation class to withstand the guaranteed basic insulation level (BIL)

Switching impulse, phase-to-ground Other for both but Routine for 345kV and above

To verify the insulation integrity of the transformer for switching stress in the field.

Partial Discharge and Radio Interference test

Routine for Class-IIOther for Class-I

To verify the integrity of the transformer insulation system to meet the guaranteed level of apparent charges occur within the transformer. 

Audible Sound Level Test Design for first unit and otherTo verify that the sound generated by the transformer does not exceed the guaranteed maximum decibel level during operation.

Dissolved gases in oil analysis Routine for Class-II Other for Class-I

To verify that the transformer had no combustible gas generation during various types of tests

CT Ratio and Polarity Routine To verify that all current transformers are connected and polarity is correct

CT Insulation Resistance RoutineTo verify that all the secondary leads of the current transformers have adequate insulation to ground all the way to the control cabinet

Operational test of all devices Routine To verify all the control wiring is correct and the auxiliary devices are operational.

Single phase impedance test Other To measure the impedance value of each set of windings separately

Sweep Frequency response Analysis test Other

To measure the response of each phase under different frequencies. This test is to verify any coil movement between different times of testing.