ELECTRIC TRANSFORMER TESTS TYPES

Today, we are going to discuss the procedure for conducting routine tests on power transformers. These tests are essential for ensuring the reliability and performance of transformers in our electrical systems. I will guide you through the key steps involved in this process.

1. **Visual Inspection**:
- Begin by thoroughly inspecting the transformer for any visible signs of damage, such as oil leaks, rust, or physical deformations. Ensure that all connections are secure and that the transformer is clean.

2. **Insulation Resistance Test**:
- Use an insulation resistance tester (megger) to measure the insulation resistance of the transformer windings. Connect the megger leads to the primary and secondary windings and the ground, and record the resistance values. This test helps identify any potential insulation breakdown.

3. **Turns Ratio Test**:
- Perform the turns ratio test to verify the ratio of primary to secondary windings. Use a turns ratio tester to apply a low voltage to the primary winding and measure the output on the secondary winding. Compare the measured ratio with the specified ratio to ensure accuracy.

4. **Winding Resistance Test**:
- Measure the resistance of the transformer windings using a micro-ohmmeter. Connect the meter to each winding, ensuring that all connections are tight and secure. Record the resistance values and compare them to the manufacturer's specifications.

5. **Vector Group Test**:
- Conduct the vector group test to confirm the phase displacement and connection configuration of the transformer. Apply voltage to the primary winding and measure the voltage on the secondary winding to verify the vector group as per the nameplate.

6. **Magnetic Balance Test**:
- Perform the magnetic balance test by applying voltage to each phase of the primary winding and measuring the induced voltages on the secondary winding. This test helps identify any issues with the core or winding connections.

7. **Dielectric Tests**:
- Conduct dielectric tests, such as the power factor test and the dielectric breakdown test, to assess the insulation condition of the transformer. These tests involve applying a high voltage to the windings and measuring the leakage current to determine the insulation's integrity.

8. **No-Load Loss and Excitation Current Test**:
- Measure the no-load losses and excitation current by energizing the transformer at its rated voltage and frequency without any load. Record the power loss and current to evaluate the core's condition and magnetizing characteristics.

9. **Load Loss and Impedance Voltage Test**:
- Conduct the load loss and impedance voltage test by applying a load to the transformer and measuring the voltage drop and power loss. This test helps determine the transformer's efficiency and impedance characteristics.

10. **Oil Tests**:
- If the transformer is oil-filled, perform oil tests to check the quality of the insulating oil. Tests such as dielectric strength, moisture content, and dissolved gas analysis provide insights into the oil's condition and the transformer's overall health.

After completing these tests, carefully analyze the results and compare them with the manufacturer's specifications and previous test data. Document all findings and address any discrepancies or issues promptly to ensure the transformer's optimal performance and longevity.

Thank you for your attention, and let's proceed with the practical demonstration of these tests.