What is RCCB? 

RCCB is a residual current circuit breaker. And this is a type of low-voltage circuit breaker. Basically RCCB is used to protect against earth leakage fault current. It has small current ratings, typically up to 160A. RCCB provides protection against electric shock. This is because the role of RCCB is primarily to detect earth leakage and trip the circuit if detected. And basically there is a test circuit operation to check if the RCCB is working or not.