Electrical Current Transformer has 4 groups for several main reasons

1. Measurement range: The four sets of windings of the Electrical Current Transformer can provide different transformation ratios, so as to realize current monitoring with different measurement ranges. Different winding ratios can make the Electrical Current Transformer suitable for different levels of current changes, from a few amps to thousands of amps or even higher.

2. Protection level: Electrical Current Transformer usually needs to meet different protection level requirements. For example, on high-voltage transmission lines, the Electrical Current Transformer needs to have high electrical isolation and protection performance to ensure the safety of equipment and personnel. Therefore, the four sets of windings of the Electrical Current Transformer can be designed according to different protection levels to meet the needs of different scenarios.

3. Testing and calibration: In order to ensure the accuracy and reliability of the Electrical Current Transformer, regular testing and calibration are essential. The four windings of the Electrical Current Transformer can be used separately for testing and calibration purposes. One of the groups is called the calibration winding, which is used to calibrate the Electrical Current Transformer during the manufacturing process; the other three groups are used for actual current measurement and monitoring.