The Full form of RCCB is Residual Current Circuit Breaker. RCCB is a differential current sensing device used to protect a low voltage circuit in case of a leakage fault. It is sometimes also known as Residual Current Device (RCD). It contains a switch device that switches off (in a fraction of second), whenever the current leaks out and does not return back through neutral. The RCCB provides protection from small current leakage arising due to accidental touch by human being or insulation, which is not possible by MCB or fuse alone. RCCB is required even when MCB is already provided because there are two types of electrical faults that are quite dangerous, first in case of high current fault arising due to short current or low resistant fault and is protected by MCB and second in case of Earth leakage arising due to cable insulation failure, accidental touch by human, etc., such faults cannot be detected by MCB, it can only be detected by RCCB. There are two types of RCCB’s available in the market i.e., the 2 pole RCCB which is used in case of single phase supply and other is 4 pole RCCB which is used in cases of a three phase supply connection.