Leakage circuit breaker is a switch that can automatically act when the leakage current in the circuit exceeds the predetermined value. The commonly used leakage circuit breaker is divided into voltage type and current type, while the current type is divided into electromagnetic type and electronic type. The voltage-type leakage circuit breaker is used in the low-voltage power grid where the neutral point of the transformer is not grounded. It is characterized by a relatively high voltage from the zero line to the ground when a person is electrocuted, causing the relay to act and the power switch to trip. Current leakage circuit breaker is mainly used in low-voltage distribution system with transformer neutral grounded. Its feature is that when a person gets an electric shock, a leakage current is detected by the zero-sequence current transformer, which makes the relay act and the power switch is disconnected.

Next, the editor of the Industrial Electrical Network will introduce the two faults and solutions encountered in the use of leakage circuit breakers. Details are as follows:

Fault 1. The leakage circuit breaker tripped as soon as it was put into operation

（1） The three-phase power line, including the zero line, does not pass through the zero-sequence current transformer in the same direction. Correct the wiring.

（2） . The circuit with and without leakage circuit breaker is electrically connected, and the two circuits can be separated.

（3） There is one fire and one ground load in the line, so it can be eliminated.

（4） The working zero line passing through the zero-sequence current transformer has the phenomenon of repeated grounding, which should be eliminated.

（5） The leakage circuit breaker is faulty and should be replaced.

Fault II. Misoperation of leakage circuit breaker

（1） Caused by overvoltage. If the circuit breaker can act when the operating overvoltage occurs in the line, the delayed or impulse voltage non-acting leakage circuit breaker can be selected, the resistance and capacitance absorption circuit can be installed between the contacts to suppress the overvoltage, and the overvoltage absorption device can also be installed in the line.

（2） Electromagnetic interference. If there is magnetic equipment or high-power electrical equipment nearby, the installation position of leakage circuit breaker should be adjusted to keep away from such electrical components.

（3） Circulation influence. If two transformers operate in parallel, they have their own grounding, because the impedance of the two transformers cannot be completely equal, which will generate a circulating current in the grounding wire, causing the circuit breaker to act, so just remove one grounding wire. In addition, the same transformer supplies power to the same load through two parallel circuits. The current in the two circuits may not be exactly the same, and there may also be circulating current. Therefore, the two circuits should be operated separately.

（4） The insulation resistance of the working zero line is reduced. When the insulation resistance of the working zero line decreases, if the three-phase load is unbalanced, a relatively large working current will appear on the zero line and flow to other branches through the ground, so that the leakage current can appear on each leakage circuit breaker, causing the circuit breaker to malfunction.

（5） Improper grounding. If the zero line is repeatedly grounded, it will cause misoperation of the leakage circuit breaker.

（6） , overload or short circuit. If the leakage circuit breaker also has short circuit protection and overcurrent protection, misoperation will occur when the setting current of the overcurrent protection release is not appropriate, and the setting current value can be adjusted at this time.