Mandatory tests of Transformers(x-formers)before handing over successfully to your customers.

1.Megger test:Megger test(Insulation resistance tests) are made to determine insulation resistance from individual windings to ground or between individual windings.?

2.Winding resisting measurements:A winding resistance test of a transformer is carried out as a type test, routine test and also as a field test.

In the factory, it helps in determining the following:

a)Calculation of the I2R(I-square-R) losses in X-formers

b)Calculation of winding temperature at the end of temperature rise test of X-formers.

c)As a benchmark for assessing possible damages in the field.

3.Voltage Ratio test:The turns ratio test is performed on all taps of every winding.The performance of a X-formers largely depends upon perfection of specific turns or voltage ratio of transformer. So it's an essential test for transformers. The voltage should be applied only in the high voltage winding in order to avoid unsafe voltage.

4. Polarity test & phase relation test:Transformer polarity is important when paralleling transformers for additional capacity or hooking up multiple single-phase transformers to form a three-phase bank.

5.No load test:No-load tests are tests that apply rated voltage in the primary side at the no-load state of the secondary side. Current only flows to the primary side in the no-load test, but this current causes excitation and iron loss of the iron core.Thus?open-circuit test?enables us to determine iron losses and parameters R0?and X0?of the?transformer.

6.Load losses at 50%,70%,100% rated load:This test is conducted to determine R01?(or R02), X01?(or X02) and full-load copper losses of the transformer.In this test, the secondary (usually low-voltage winding) is?short-circuited?by a thick conductor and variable low voltage is applied to the primary.There is no output from the?transformer?under?short-circuit?conditions.Therefore, input power is all loss and this loss is almost entirely copper loss. It is because the iron loss in the core is negligibly small since the voltage VSC?is very small.?

7.Percantage Impedance measurements:?The impedance of a transformer is the total opposition offered to alternating current. This may be calculated for each winding.However, a rather simple test provides a practical method of measuring the equivalent impedance of a transformer without separating the impedance of the windings.When referring to the impedance of a transformer, it is the?equivalent impedance?that is meant.

8.Di electric test:?Also known as x-former oil test .Testing sequences and procedures are defined by various international standards.The transformer oil (insulation oil) of voltage transformers and current transformers fulfills the purpose of insulating as well as cooling. Thus, the dielectric quality of transformer oil is essential to secure operation of a transformer.

9.Power frequency high voltage withstand test:?Intended to check the the ability of main insulation to earth and between winding.The test shall be performed on all the windings one by one.

10.Temperature rise test:?A temperature rise test of a transformer?is an important test which should be included in any type test of an oil transformer. In this test, we check whether the temperature rising limit of the transformer winding and transformer oil is as specified by the manufacturer.

11.Induced over voltage test:?Required to ensure the security that the insulation between the phase windings, turns, coils, tapping leads and terminals.This test checks the inter term insulation.?For a 11 KV/433 V transformer, 866 volts are applied at the 433 V winding with the help of a generator for 1 minute. This induces 22 KV on 11 KV side. The frequency of the 866 V supply is also increased to 100 Hz.

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