Transformers
Transformers
Posted By MMASBA

Transformer Testing


Transformer testing

Transformer testing is one of the most important lectures so; you must read carefully and take your time to understand these tests… surly you ask why transformer tests are important? and what we use to do these tests?, i will answer this questions and more.

Firstly why we do these transformer tests?

  • We do transformer testing to collect some information about transformer efficiency, losses and reliability record of transformers in service.These tests for single phase and three phase transformers and we perform various tests on the transformer also to ensure that the required technical specifications of the transformer and to analyze the performance of the transformer.

Secondly what is the specifications and codes that we use to do these tests?

  • Transformer testing carried out in accordance with applicable IEC and ANSI specifications, unless otherwise specified in the contract documents. Where the test procedure is not specified, the requirements of IEC 60076 apply.

We can classify transformer testing according to:

1- Electrical type transformer testing.

2- Electrical routine transformer Testing.

3- Electrical special transformer tests.

4- Pre-commissioning and commissioning tests.

5- Periodic maintenance transformer tests.

6- Emergency tests.

From the previous classifications, we can deduce that the first, second and third types of transformer testing are carried out by the factory which manufactured the transformer. For the fourth, fifth and sixth types, they are carried out at the work site of the transformer.

Now we will identify the 6 types of tests mentioned above:

1- Electrical type transformer testing.

The manufacturer who manufactured the transformer do this test to ensure that the practical measurements are consistent with the theoretical tests and also the simulations .

These tests are carried out by the manufacturer on a prototype only of the production of that transformer and not on all the transformers produced .. why ? Because, some tests (such as short circuits) affect the life time of the transformer, these tests are such as:

  1. Transformer Turns ratio test.
  2. Transformer winding resistance measurement.
  3. Insulation resistance test of transformer.
  4. Open circuit test of transformer.
  5. Short circuit test of transformer.
  6. Induced over voltage test of transformer.
  7. Separate-source voltage withstand test.
  8. Partial discharge test of transformer.
  9. Lightening impulse test (Dielectric type test)
  10. Temperature rise test.
  11. Vector group test.
  12. Measurements of dissipation factor.
  13. Oil tests.

2- Electrical routine transformer testing.

These tests are part of the electrical type transformer testing.

The manufacturer carry out Electrical routine tests to verify the operation efficiency and the life time of the transformer and these tests are carried out on all manufactured transformers.

These tests include the following:

  1. Transformer Turns ratio test.
  2. Transformer winding resistance test.
  3. Insulation resistance test of transformer.
  4. Open circuit test of transformer.
  5. Short circuit test of transformer.
  6. Induced over voltage test of transformer.
  7. Separate-source voltage withstand test.
  8. Partial discharge test of transformer.

3- Electrical special transformer tests.

the manufacturer carry out these tests to obtain important information which assist the user during operation and maintenance of the transformer.

 Tests include the following:

  1. Sound level measurement.
  2. Measurement of zero sequence impedance.
  3. Measurement of the harmonics of the no-load current.

4- Pre-commissioning and commissioning tests.

These tests are carried out at the work site of the transformer in order to ensure that the results of the tests carried out in the factory match with the results obtained at the site before the operation of the transformer as the transformer may pass the tests at the factory, but when it is supplied to the site fails in some tests due to the stresses During factory tests.

These tests are part from routine tests.

5- Periodic maintenance transformer tests.

We perform these tests on the site after operation of the transformer, also they are carried out on a regular basis and there is a weekly, monthly and annual maintenance plan to ensure the efficiency and performance of the transformer so, the periodic maintenance plans vary according to the type of transformer. moreover these tests are  performed to detect faults in their early stages such as measuring insulation resistance so, If their value falls below normal, this indicates the beginning of problems in isolation.

 6- Emergency tests.

We carry out These tests at the site if the transformer has some problems during operation such as high temperature of the windings, although the ventilators work very efficiently,

Then we can test the measurement of resistance to windings or analysis of oil used for cooling.

In conclusion:

Therefore, we know that there are many types of transformer testing done at factory or at the work site of the transformer as mentioned above and all revolve around the same tests.

so, we will show all the tests in details and each test will be mentioned separately to which type of tests belongs.

This is a list of all the tests done on the transformer: (Click on any address to get the full details of this test)


Electrical Engineer