The abbreviation RCBO comes from: “Residual Current Breaker with Over-Current” which means earth leakage protection breaker as well as overload protection. In other words, the RCBO functions as MCB as well as the RCD which protects against the earth leakage.
Hence the RCBO works to protect the electrical circuit from three types of events:
1- Earth Leakage:
The earth leakage current is the current that leaves the electric circuit for earth. This can happen in many types of cases Including but not limited to the events that result in a defect in the insulation of the electrical wires. This leads to an earth leakage current especially when the surrounding environment is highly conductive such as the presence of water and others.
The real and most important purpose is to protect humans from electric shock, which may lead to death, God forbid. It occurs when humans come into contact with an electrical conductor in a highly conductive environment (such as wet places or in direct contact with highly conductive materials such as iron) cause a leakage of an earth current passing through the human body.
2- Electrical short circuit:
This occurs when there is a direct contact between live conductors or with neutral conductor without the resistance normally provided by the circuit, the electric current would rush around the circuit in a loop and the electric current would multiply thousands of times in just a fraction of a second.
3- Over Current:
Over current means that the electric current resulting from normal loads exceeds the capacity of electrical conductors. For example, an increase in current beyond the maximum capacity of a particular electrical wire, which may lead to the collapse of the insulating layer or a rise in the temperature of the wire, which may lead to fire.
In summary, the RCBO is a special breaker as it enables unique and high protection capabilities and there are hardly any kind of electrical hazards that the RCBO breaker does not protect against especially in home and commercial applications.