Transformers Testing

Testing Of Transformers
The studies conducted have revealed that with 6* increase in insulation temperature over permissible value the life of transformer gets reduced by about 50%. The efficient working of the transformer and its reliability is very important for the power system performance. This can only be achieved by using quality materials, ensuring high standards of workmanship during production. Various tests are carried out at different stages of manufacturing process. The final tests on fully assembled transformer also assure suitability of the equipment for satisfactory performance. Our tests are conducted in compliance to IS2026/1EC726/BS171 to ensure reliable and efficient performance of the transformer during its lifetime.
1. Measurement of winding resistance
2. Verification of voltage ratio
3. Verification of vector group
4. Measurement of no load current and losses
5. Measurement of impedance and load losses
6. Measurement of insulation resistance
7. Power frequencies withstand voltage
8. Induced over voltage test
9. Air presser test

Type Tests
1. Impulse voltage withstand test
2. Temperature rise test

TEST
The ratio should be checked at all taps and between all the windings. It is checked by applying a single-phase 230V (approx) supply on the high voltage side and measuring the voltage on the low voltage side at all tap positions. The measured voltage on LV side shall conform to declining trend between tap (min) to tap (max) position for all phases. Polarity and interphone connections are checked while measuring the ratio. This can be checked by the avometer method. The primary and secondary windings are connected together at points indicated in sketch shown below. A low voltage three-phase supply is then applied to the HV terminals. Readings obtained should be the vectorial sum of the separate voltages of each winding under consideration.