How often do current transformers need to be calibrated?

The calibration cycle of current transformers is usually once every 1 to 3 years. The specific calibration cycle depends on many factors, including the frequency of use of the equipment, the working environment, and the manufacturer's recommendations. For example, for some high-precision current transformers, such as 0.2-level or 0.2S-level, more frequent calibration may be required.
Calibration steps
When calibrating a current transformer, the following steps are usually required:
1. Wiring: Connect the primary side of the standard current transformer and the current transformer to be tested in series to the output circuit of the booster, and connect the secondary side to the corresponding input terminals of the calibrator.
2. Parameter setting: Set the rated primary current, rated secondary current, rated frequency, and rated secondary load parameters on the calibrator.
3. Current boost and test: Slowly adjust the output current of the booster, gradually increase from zero to the rated primary current value of the current transformer to be tested, and test at multiple current points (such as 5%, 10%, 20%, 50%, 100% of the rated current).
4. Data recording: record the ratio error (ratio error) and angle error (phase error) data displayed by the calibrator.
5. Current reduction and wire removal: After completing all tests, slowly adjust the current booster to reduce the output current to zero, and then remove the connecting wires.
Preparation before calibration
1. Personnel requirements: The calibrator should be familiar with the working principle, calibration method and relevant safety regulations of the current transformer.
2. Environmental conditions: Calibration should be carried out under relatively stable environmental conditions. The ambient temperature is generally required to be (20±5)℃ and the relative humidity does not exceed 80%.
3. Equipment inspection: Check and debug calibration equipment such as standard current transformers, current load boxes, current boosters, and calibrators.
Calibration result judgment and processing
Determine the error level of the current transformer based on the readings of the calibrator. If the error exceeds the allowable range, the equipment may need to be repaired or replaced.
Self-calibration function
Some advanced current transformers have a self-calibration function, which performs 1:1 self-calibration through the built-in dual secondary winding, greatly reducing the total power demand of the measurement circuit.