How to test the error of a current transformer after compensation?

I. Test Method Selection

1. Comparison Method

Operation: Simultaneously energize a high-precision standard current transformer and the current transformer under test, and read the error value using a calibrator.

Applicable to: Field testing; accuracy is limited by the standard current transformer.

Example: For 0.5 class current transformers, the ratio difference must be within ±0.5%, and the phase difference ≤30′.

2. Bridge Method

Operation: Adjust the bridge balance and calculate the error using impedance.

Applicable to: Laboratory environment; high accuracy.

3. Digital Measurement Method

Operation: Acquire the signal using digital measuring equipment and process it to obtain the error value.

Applicable to: High-precision measurement; high degree of automation.

II. Test Steps

1. Preparation

Demagnetize the current transformer under test and check the wiring.

Apply a sinusoidal current at rated frequency, and connect the specified load to the secondary side.

2. Testing

Use a calibrator to read the ratio difference and phase difference.

Record the data and compare it with the accuracy class limits.

3. Verification

The compensated error must return to within the limits.

For protective transformers, ensure that it does not affect protection operation.

III. Precautions

Environmental Control: Temperature, humidity, and electromagnetic interference will affect the results.

Wiring Specifications: Ensure correct polarity and avoid short circuits.

Instrument Selection: A 0.05S-class error tester is recommended, supporting ratio and polarity detection.