When a fault occurs in the circuit, the current flowing through the relay under normal conditions is the rated value that flows during normal operation. When a fault occurs, due to the change of the impedance of the line, the residual current circuit breaker makes the current passing through the relay exceed its rated value, and the relay contacts quickly break and cut off the power supply to protect the line.

The residual current circuit breaker is mainly used to disconnect the grounding short-circuit current. Generally, the grounding current is not very large due to the grounding resistance, so the circuit breaker may not operate. Therefore, some circuits need to be equipped with leakage protection, so the measurement of leakage protection is based on zero sequence. The current transformer will act as soon as the three phases are unbalanced.

The residual current circuit breaker is suitable for AC voltage to AC400V, frequency 50HZ, and rated current to 1250A and below in low-voltage power grids. Possible fire hazard due to detected long-standing ground faults.

The residual current circuit breaker is determined by the characteristics of the leakage detection element, the residual current transformer. The residual current transformer has a toroidal core, the secondary coil is wound on the core, and the primary coil is the wire passing through the inner hole of the core.

The residual current circuit breaker realizes the protection action by detecting the current vector sum of the phase line and the current difference between the neutral line and the neutral line. The sensitivity is higher than that of the zero-sequence protection. Generally, it has two purposes. One is to prevent fire (300~500MA), and it is used for trunk lines.

The residual current circuit breaker is one of the important electrical equipment in the low-voltage power distribution system. It is a switching device used to cut off and distribute the overcurrent and short-circuit faults generated in the circuit. oxidation reaction to extinguish the arc.