Potential transformer(PT) testing

Commissioning and maintenance tests for potential transformers (PTs) are essential to ensure their accurate and reliable operation. Here are some of the commonly performed tests:

Ratio test: This test verifies the turns ratio of the PT by comparing the voltage applied to the primary winding with the voltage measured on the secondary winding. The expected ratio should match the manufacturer's specifications.

Polarity test: This test confirms the correct polarity of the PT's winding connections. A known voltage is applied to the primary winding, and the resulting secondary voltage is observed. The polarity should match the reference polarity for correct operation.
Insulation resistance test: This test measures the insulation resistance between the primary and secondary windings and between each winding and the ground. It helps identify any insulation breakdown or leakage issues.

Winding resistance test: The winding resistance of the primary and secondary windings is measured to ensure they are within acceptable limits. Deviations from the expected resistance values may indicate issues like loose connections or winding damage.

Burden test: The burden test measures the accuracy of the PT by applying a known voltage to the primary winding and measuring the secondary voltage under rated load conditions. The measured secondary voltage should be within an acceptable range of the expected value.

Frequency response test: This test evaluates the frequency response of the PT to ensure it operates accurately across the specified frequency range. A sinusoidal voltage at different frequencies is applied, and the secondary output is compared to the input.

Dielectric strength test : This test assesses the insulation integrity of the PT by subjecting it to a high voltage (e.g., two times the rated voltage) for a specific duration. It ensures that the insulation can withstand expected voltage stresses without breakdown.

In addition to these commissioning tests, regular maintenance checks are necessary to ensure ongoing reliability. Maintenance activities may include visual inspections, cleaning of terminals and connections, tightening of bolts, lubrication if applicable, and periodic calibration checks.

It's important to consult the manufacturer's documentation and guidelines for specific test procedures and recommended maintenance intervals for the particular PT model you are working with. Additionally, it is often beneficial to involve qualified personnel or specialized testing services to perform these tests, especially for critical applications or high-voltage systems.