Types and principles of residual current operated circuit breakers:

       Residual current operated circuit breakers have two types of composition:

       One approach is to install a leakage detection unit in a molded case circuit breaker, transforming it into a residual current device circuit breaker;

       Another approach is to equip a miniature circuit breaker with a residual current protection module to form a residual current protective circuit breaker. Depending on the number of miniature circuit breakers, single, double, triple, and quadruple residual current protective circuit breakers can be constructed.

       The overload and short-circuit protection characteristics of a residual current circuit breaker are identical to those of similar circuit breakers, while its residual current protection characteristics depend on the residual current detection unit or residual current protection module.

       The basic working principle of a leakage protector is as follows:

       The principle behind leakage protection relies on the fact that the vector sum of currents passing through a zero-sequence current transformer during a leakage fault is not equal to zero. This is based on the condition that under fault conditions, the phase current vectors are not equal to zero, resulting in a zero-sequence current. When the zero-sequence current reaches a set value, it activates the release, cutting off the fault current for protection purposes. A leakage protector is an effective measure to prevent electrical fires and electric shock accidents caused by insulation damage between the phase lines and exposed conductive parts of electrical devices (including metal equipment enclosures, laying pipe slots, etc.), conductive parts outside the device (including water, heating pipes, and building structures, etc.), and the earth in low-voltage distribution systems.

       Currently, the leakage protectors produced domestically are divided into two major categories: electromagnetic and electronic. The working principle of electromagnetic leakage protectors is that a zero-sequence current transformer detects the zero-sequence current in the circuit, and the resulting electromagnetic field weakens the electromagnetic field of the permanent magnet, causing the energy storage spring to release the armature, the release mechanism to actuate, the switch to trip, and the faulty circuit to be cut off. Electronic leakage protectors, on the other hand, utilize the voltage of the secondary winding of the zero-sequence current transformer, which is amplified electronically to generate sufficient power to trip the switch. Currently, electronic leakage protectors are widely used in civil buildings. Here, we mainly introduce the application of the residual current circuit breaker's leakage protection function.