A leakage circuit breaker is a switch that can automatically operate when the leakage current in the circuit exceeds a predetermined value. Commonly used earth leakage circuit breakers are divided into two types: voltage type and current type, and current type is divided into two types: electromagnetic type and electronic type. Voltage leakage circuit breaker is used in low-voltage power grids where the neutral point of the transformer is not grounded. Its characteristic is that when a person gets an electric shock, a relatively high voltage appears between the neutral line and the ground, causing the relay to operate and the power switch to trip. Current leakage circuit breakers are mainly used in low-voltage 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, causing the relay to operate and the power switch to disconnect.
Below, the editor of the Industrial Electrical Appliances Network will introduce to you two faults encountered when using leakage circuit breakers and their solutions. The details are as follows:
Fault 1. The leakage circuit breaker tripped just after it was put into operation.
(1) The three-phase power lines, including the neutral line, do not pass through the zero sequence current transformer in the same direction. Just correct the wiring.
(2) If the circuit with the leakage circuit breaker installed and the circuit without the leakage circuit breaker are electrically connected, just separate the two circuits.
(3) There are one fire and one ground loads in the line, just eliminate such loads.
(4) The working neutral line passing through the zero-sequence current transformer has repeated grounding, and repeated grounding should be eliminated.
(5) The leakage circuit breaker itself is faulty and should be replaced.
Fault 2. The leakage circuit breaker malfunctioned during operation.
(1) Caused by overvoltage. For example, when an operating overvoltage occurs in the line to cause the circuit breaker to operate, you can choose a delay or impulse voltage non-operating leakage circuit breaker, or install a resistance-capacitance absorption circuit between the contacts to suppress the overvoltage, or you can An overvoltage absorption device is installed in the line.
(2) Electromagnetic interference. If there are magnetic equipment or high-power electrical equipment running or stopping nearby, the installation position of the leakage circuit breaker should be adjusted to keep away from such electrical components.
(3) Circulation influence. If two transformers operate in parallel, each has its own grounding. Since the impedances of the two transformers cannot be completely equal, this will produce circulating current in the grounding wire, causing the circuit breaker to operate. Simply remove one grounding wire. 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, or circulating current may occur. Therefore, the two circuits should be operated separately.
(4) The insulation resistance of the working neutral line is reduced. When the insulation resistance of the working neutral line is reduced, if the three-phase load is unbalanced, a relatively large working current will appear on the neutral line and flow to other branches 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 grounded repeatedly, it will cause the leakage circuit breaker to malfunction.
(6) Effects 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 tripper is inappropriate. At this time, just adjust the set current value.