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Operating condition

Power transformer is an electric machine with a useful life cycle of some 30 years. This doesn’t mean to say that cannot be used above this time, in fact, a great part of the electric and industrial fleet is being operated with reliable machines above this time.

Power Transformer Maintenance and Field Testing
Power Transformer Maintenance and Field Testing (on photo: Monophase transformer turns ratio unit, from Megger Company, model TTR100)

The really important fact is to know the status and evolution of the transformer to be in conditions to operate it with the maximum security and know if it is appropriate to continue it’s use, know overload capacity, limit load, refurbish it or either take it out from active service.


Field testing of a transformer

As a result of the owner company, the importance of the machine and the outage possibilities, it is necessary to perform on each transformer a fitted maintenance program with a test protocol previously accorded.

Breakdown of the dielectric system in a power transformer column
Breakdown of the dielectric system in a power transformer column

Next will be indicated a series of test that can set up this program and that are something like a continuation of validation tests performed when manufacturing the transformer – but adapted to field testing.

We have to take under account that in the field, in transformer installations, is not usually possible to have bulky equipment, what states certain limitations to field test with respect to manufacturing ones.

Described tests are chosen from the commercially available ones, standardized and usual into test programs.


Magnetic / Electric Circuit Tests

Those will be performed wit portable instrumentation (easily transported in vehicle/test van) of a series of measurements that allow obtaining base parameters from the transformer. It will be studied the punctual status to perform a diagnose and parameter trending values to perform scheduled works. All this tests are off-line.

Electric / Magnetic field testing:

  • No-load test. Turns Ratio (TTR). Polarity, connection group y excitation current.
  • Load test (short circuit test, impedance measurement).
  • Winding resistance.
  • Frequency response analysis (FRA).

There is a group of maintenance techniques that from an electric point of view and through some field tests are going to allow us to trace the transformer status as indicated and in the case of breakdown diligently detect the real problem and perform the required actions.

Title:Power Transformer Maintenance and Field Testing – Andrés Tabernero García
Format:PDF
Size:1.87 MB
Pages:19
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Power Transformer Maintenance and Field Testing
Power Transformer Maintenance and Field Testing

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4 Comments


  1. Shammy Peterson
    Sep 01, 2021

    It sure was nice when you said that it is necessary to perform field testing to check outage possibilities. This is something that must be considered by manufacturing companies, especially if their operations heavily rely on a working transformer. I could imagine how companies must consider hiring a professional for transformer field maintainance services.


  2. Pradeepsinh
    Feb 08, 2020

    Good information


  3. Prasant K. Banerjee
    Jul 29, 2014

    This brochure will be very helpful to me & our Company. Thanks for your guide.


  4. Mubita mwala
    Jul 29, 2014

    This is my field i think i have serviced about a hundred Tx in the short period i had a job this is good

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