How to Troubleshoot Wiring Errors in Current Transformers?

Based on your question, I have compiled a method for troubleshooting wiring errors in current transformers. The troubleshooting process mainly focuses on key points such as wiring direction, polarity, grounding, and circuit integrity.
1. Check the Wiring Direction
First, you need to confirm whether the direction of the primary side (wiring part) of the current transformer is correct. The correct wiring direction is for the power line to enter from the P1 terminal of the transformer and exit from the P2 terminal. If the direction is reversed, it will lead to abnormal meter readings, such as the reading decreasing when the power consumption increases. If you find that the wiring is incorrect and it is inconvenient to rewire, you can remedy this by adjusting the secondary side wiring (such as swapping terminals 1 and 2).
2. Verify Polarity Connection
Reversed polarity is one of the common errors. Correct wiring should ensure that when the primary current enters from P1 and exits from P2, the secondary current exits from S1 and enters from S2 (i.e., "subtractive polarity" connection). If the polarity is reversed, it will cause the measuring instrument (such as an ammeter or watt-hour meter) to be biased or cause measurement errors. You can use the DC method (battery instantaneous method) or AC method (voltage comparison method) to verify the polarity.
3. Ensure Reliable Grounding
The secondary side of the current transformer must have a reliable ground connection, usually by grounding the S2 terminal of the secondary winding. This is to prevent high voltage from the primary side from entering the secondary side in case of insulation breakdown between the primary and secondary windings, endangering personal and equipment safety. At the same time, avoid multiple grounding points to prevent false tripping of the protection device.
4. Check Circuit Integrity
You need to check whether there is a short circuit or open circuit in the secondary circuit of the current transformer. Pay close attention to whether the connections of the secondary circuit wires are secure, and whether there are any loose connections, poor contact, or overheating in intermediate contacts, fuses, and test connection boxes. In addition, the cross-sectional area of ​​the secondary circuit wires should meet the requirements; generally, the voltage circuit should be no less than 2.5mm², and the current circuit should be no less than 4mm².
5. Measurement and Verification
During the troubleshooting process, you can measure the current of each phase and the neutral line current of the current transformer and observe whether the values ​​are reasonable. If you find that the meter reading does not match the actual electricity consumption, in addition to checking the wiring, you should also confirm whether the current ratio of the current transformer matches that of the meter. For example, if the current transformer ratio is 100:5, the meter reading needs to be multiplied by 20 to get the actual electricity consumption.