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What are various type of tests to be performed on Power Transformer ?

Updated: Apr 11, 2021


There are various Test required on Transformer to conform performance of Transformer.

Mainly two types of tests are done by manufacturer before dispatching the transformer mainly

(1) Type test of transformer

(2) Routine test.

In addition some other tests are also carried out by the consumer at site before commissioning and also periodically in regular & emergency basis throughout its life.

Transformer Testing mainly classified in

Transformer Tests done by Manufacturer

  • (A) Routine Tests

  • (B)Type Tests

  • (C) Special Tests

Transformer Tests done at Site

  • (D) Pre Commissioning Tests

  • (E) Periodic/Condition Monitoring Tests

  • (F) Emergency Tests

(A) Routine tests:

  • A Routine test of transformer is mainly for confirming operational performance of individual unit in a production lot. Routine tests are carried out on every unit manufactured.

  • All transformers are subjected to the following Routine tests:

  • Insulation resistance Test.

  • Winding resistance Test.

  • Turns Ration / Voltage ratio Test

  • Polarity / Vector group Test.

  • No-load losses and current Test.

  • Short-circuit impedance and load loss Test.

  • Continuity Test

  • Magnetizing Current Test

  • Magnetic Balance Test

  • High Voltage Test.

  • Dielectric tests

  • Separate source AC voltage.

  • Induced overvoltage.

  • Lightning impulse tests.

  • Test on On-load tap changers, where appropriate.

(B) Type tests

  • Type tests are tests made on a transformer which is representative of other transformers to demonstrate that they comply with specified requirements not covered by routine tests:

  • Temperature rise test (IEC 60076-2).

  • Dielectric type tests (IEC 60076-3).

(C) Special tests

  • Special tests are tests, other than routine or type tests, agreed between manufacturer and purchaser.

  • Dielectric special tests.

  • Zero-sequence impedance on three-phase transformers.

  • Short-circuit test.

  • Harmonics on the no-load current.

  • Power taken by fan and oil-pump motors.

  • Determination of sound levels.

  • Determination of capacitances between windings and earth, and between windings.

  • Determination of transient voltage transfer between windings.

  • Tests intended to be repeated in the field to confirm no damage during shipment, for example frequency response analysis (FRA).

(D) Pre commissioning Tests

  • The Test performed before commissioning the transformer at site is called pre commissioning test of transformer. These tests are done to assess the condition of transformer after installation and compare the test results of all the low voltage tests with the factory test reports.

  • All transformers are subjected to the following Pre commissioning tests:

  • IR value of transformer and cables

  • Winding Resistance

  • Transformer Turns Ratio

  • Polarity Test

  • Magnetizing Current

  • Vector Group

  • Magnetic Balance

  • Bushing & Winding Tan Delta (HV )

  • Protective relay testing

  • Transformer oil testing

  • Hipot test

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