The leakage circuit breaker is a switch that can automatically act when the leakage current in the circuit exceeds a predetermined value. Commonly used leakage circuit breakers are divided into two types: voltage type and current type, and current type is divided into electromagnetic type and electronic type. Voltage-type earth leakage circuit breakers are used in low-voltage power grids where the neutral point of the transformer is not grounded. Its characteristic is that when a person is electrocuted, a relatively high voltage appears on the neutral line to the ground, causing the relay to act and the power switch to trip. Current-type earth leakage circuit breakers are mainly used in low-voltage power distribution systems where the neutral point of the transformer is grounded. Its characteristic is that when a person gets an electric shock, a leakage current is detected by the zero-sequence current transformer, so that the relay operates and the power switch is disconnected.

The following small series of industrial electrical network will introduce the two faults and solutions encountered by the use of leakage circuit breakers. The details are as follows:

Fault 1. The leakage circuit breaker trips as soon as it is 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, and the wiring can be corrected.

(2) There is an electrical connection between the installation of the leakage circuit breaker and the circuit without the leakage circuit breaker, and the two circuits can be separated.

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

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

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

Fault 2. Malfunction of leakage circuit breaker operation

(1) Caused by overvoltage. For example, when the operating overvoltage occurs in the line, the circuit breaker can be activated. At this time, the delay or impulse voltage non-action type leakage circuit breaker can be selected, or a resistance-capacitance absorption circuit can be installed between the contacts to suppress the overvoltage. Invest in overvoltage absorption devices in the line.

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

(3) The influence of circulation. If two transformers are operated in parallel, they have their own grounding, because the impedances of the two transformers cannot be completely equal, which will cause a circulating current in the grounding wire, causing the circuit breaker to act, and one grounding wire can be removed. In addition, the same transformer supplies power to the same load through two parallel circuits, and the currents in the two circuits cannot be exactly the same, and circulating currents may also occur. 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 neutral line decreases, if the three-phase load is unbalanced, a relatively large working current will appear on the neutral line and flow to other branch circuits through the ground, so that leakage current can appear on each leakage circuit breaker , causing the circuit breaker to malfunction.

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

(6) The influence of overload or short circuit. If the leakage circuit breaker has short-circuit protection and over-current protection at the same time, malfunction will occur when the set current of the over-current protection release is inappropriate, and the set current value can be adjusted at this time.