How to Perform Transformer Turns Ratio Test

Performing a transformer turns ratio (TTR) test involves several steps to ensure that the transformer's winding ratios are accurate and within specified tolerances. Here is a step-by-step guide to performing a TTR test:

Step-by-Step Guide for Transformer Turns Ratio (TTR) Test

1. Preparation and Safety:

• De-energize the transformer: Ensure the transformer is de-energized and properly grounded before beginning the test.
• Verify Safety Procedures: Confirm that all safety protocols are in place to protect personnel and equipment.
• Inspect the Transformer: Check for any visible signs of damage or issues that might affect the test results.

2. Gather Equipment:

• TTR Tester: Ensure you have a calibrated and reliable TTR test instrument.
• Connection Cables: Use appropriate test leads and connection cables.
• Protective Gear: Wear necessary personal protective equipment (PPE).

3. Set Up the TTR Tester:

• Connect the High Voltage Lead: Connect the high voltage lead of the TTR tester to the high voltage winding of the transformer (primary winding).
• Connect the Low Voltage Lead: Connect the low voltage lead of the TTR tester to the low voltage winding of the transformer (secondary winding).
• Ground the Tester: Ensure the tester is properly grounded to prevent any potential hazards.

4. Configure the TTR Tester:

• Input Transformer Details: Enter the transformer nameplate data, such as the rated primary and secondary voltages.
• Select Test Parameters: Set the test parameters according to the manufacturer's guidelines or industry standards.

5. Perform the Test:

• Initiate the Test: Start the test using the TTR tester. The tester will apply a low voltage to the primary winding and measure the voltage induced in the secondary winding.
• Record the Measurements: The TTR tester will display the measured turns ratio. Record these values for each tap position if the transformer is equipped with a tap changer.

6. Analyze Results:

• Compare with Nameplate Ratio: Compare the measured turns ratio with the transformer's nameplate ratio.
• Calculate Ratio Error: Determine the percentage error between the measured and nominal ratios. The formula for percentage error is:$$\text{Percentage Error} = \left( \frac{\text{Measured Ratio} - \text{Nameplate Ratio}}{\text{Nameplate Ratio}} \right) \times 100\%$$
• Evaluate Tolerances: Check if the ratio error is within acceptable tolerances as specified by the applicable standards (e.g., IEEE, IEC).

7. Repeat for All Phases and Taps:

• Multiple Phases: For three-phase transformers, perform the test on all three phases (A-B, B-C, C-A).
• Tap Positions: If the transformer has multiple taps, repeat the test for each tap position to ensure accurate ratio measurements across the entire range.

8. Document the Test Results:

• Test Report: Compile the test results into a comprehensive report. Include the transformer's nameplate information, test parameters, measured ratios, and any observations or anomalies.
• Recommendations: Provide recommendations based on the test results, such as maintenance actions or further investigations if any discrepancies are found.

Important Considerations

• Environmental Conditions: Conduct the test in a stable environment to avoid temperature and humidity affecting the readings.
• Calibration: Ensure that the TTR tester is calibrated and certified for accuracy.
• Manufacturer Guidelines: Always refer to the transformer's manufacturer guidelines and standards for specific test procedures and acceptable tolerances.

References

• Guide on TTR Testing

• TTR Testing Procedures

This comprehensive approach ensures accurate and reliable measurement of the transformer's turns ratio, aiding in the detection of winding issues or anomalies.

Aug 10,2024