Analysis of the causes of refusal and malfunction of leakage circuit breaker

The phase and neutral lines pass through a toroidal core as the primary line set of the current transformer, while the secondary side is connected to the trip unit. When the circuit is operating normally, the current of the phase line is equal to the neutral, and the vector sum of the currents is equal to zero. However, if the circuit fails and the current is grounded, the currents of the phase and neutral lines cannot be balanced, and the sum of the current vectors is not equal to zero. The secondary line group of the current transformer senses this situation, and after the electronic amplification circuit, the leakage circuit breaker is tripped, and the circuit leading to the load is cut off. When the residual current is between 50% and 100% of the rated trip current, the leakage circuit breaker trips.

Refuse and malfunction of leakage circuit breaker:

1. Reasons for the rejection of the leakage circuit breaker

1) In the TN-CS system, if the detection circuit is between the PEN line and the L line of the TN-C segment and the leakage occurs on the PE line of the TN-S segment, the leakage circuit breaker will refuse to operate;

2) In the TN-S system, since the installer of the circuit connects the N line to the access switch, if the N line is disconnected, when the leakage occurs on the L line, the leakage circuit is not detected by the detection circuit, and the leakage is broken. Will refuse to act;

3) In the TN-C=S system, the circuit installer connects the N-line and the PE line together (to explain, it should mean that the PE line also enters once before or at the power line of the leakage breaker). The toroidal core of the winding is inside), if leakage occurs, the leakage circuit breaker will refuse to operate;

4) When installing and using, the sensitivity of the leakage circuit breaker is too low, and the actual leakage value does not reach the specified value, it will also refuse to operate.

2. The cause of the malfunction of the leakage circuit breaker

1) In the TN-CS system, the installer will reverse the PF line and the N line, causing malfunctions;

2) In the three-phase four-wire circuit of lighting and power, the three-pole leakage protector is selected incorrectly, and the zero line of the load is directly connected to the power supply side of the protector to cause malfunction;

3) There are high-power electrical appliances near the leakage protector, and electromagnetic interference generated when the electrical appliance is opened or closed may cause malfunction;

4) The phase and neutral insulation resistance is too low, and some current leakage points leak to the earth, causing the current vector through the zero-sequence current transformer to be malfunctioning when the circuit is normal. (line leakage)

5) When the grounding wire of the electrical equipment casing is connected to the working zero line, it may cause a malfunction;

6) The three-phase power line through the three-phase leakage protector does not pass the current transformer in the same direction. Cause a malfunction;

7) When installing and using, the sensitivity of the leakage circuit breaker is too high, which will cause malfunction.