Some tests are done at manufacturer premises before delivering the transformer. Mainly two types of transformer testing are done at manufacturer premises- type test of transformer and routine test of transformer. In addition to that some transformer tests are also carried out at the consumer site before commissioning.
Type of Transformer Testing:Tests done at factory
1. Type tests
2. Routine tests
3. Special tests
Tests done at site
1. Pre-commissioning tests
2. Periodic/condition monitoring tests
3. Emergency tests
Type Test of Transformer
To prove that the transformer meets customer’s specifications and design expectations, the transformer has to go through different testing procedures in manufacturer premises. Some transformer tests are carried out for confirming the basic design expectation of that transformer. These tests are done mainly in a prototype unit not in all manufactured units in a lot. Type test of transformer confirms main and basic design criteria of a production lot. Type tests of transformer includes :
1. Transformer winding resistance measurement
2. Transformer ratio test.
3. Transformer vector group test.
4. Measurement of impedance voltage/short circuit impedance (principal tap) and load loss (Short circuit test).
5. Measurement of no load loss and current (Open circuit test).
6. Measurement of insulation resistance.
7. Dielectric tests of transformer.
8. Tests on on-load tap-changer.
9. Vacuum tests on tank and radiators.
Routine Tests of Transformer
Routine tests of transformer is mainly for confirming operational performance of individual unit in a production lot. Routine tests are carried out on every unit manufactured. These tests are:
1. Transformer winding resistance measurement.
2. Transformer ratio test.
3. Transformer vector group test.
4. Measurement of impedance voltage/short circuit impedance (principal tap) and load loss (Short circuit test).
5. Measurement of no load loss and current (Open circuit test)
6. Measurement of insulation resistance.
7. Dielectric tests of transformer.
8. Tests on on-load tap-changer.
9. Oil pressure test on transformer to check against leakages past joints and gaskets. That means Routine tests of transformer include all the type tests except temperature rise and vacuum tests.
Special Tests of Transformer
Special tests of transformer is done as per customer requirement to obtain information useful to the user during operation or maintenance of the transformer:
1. Dielectric tests.
2. Measurement of zero-sequence impedance of three-phase transformers
3. Short-circuit test.
4. Measurement of acoustic noise level.
5. Measurement of the harmonics of the no-load current.
6. Measurement of the power taken by the fans and oil pumps.
7. Tests on bought out components / accessories such as Buchholz relay, temperature indicators, pressure relief devices, oil preservation system etc.
Source: bornika.ir
