An RCD is a sensitive circuit breaker that automatically shuts off power to a circuit when it detects a power imbalance or earth leakage.
Because of the potential harm from electric shocks, RCDs must shut off power within a specific timeframe and leakage current. This is usually 30 milliamps for 300 milliseconds.
RCDs have a current rating which must not be surpassed to avoid damage to the device.
An RCDs should be disconnected from a circuit before doing an insulation resistance test. Again, this is to prevent damage to the protective device.
An RCDs senses earth leakage by comparing the neutral potential at the earth bar and the neutral coming from the electrical appliance with the fault.
If current is leaking to earth, there will be a difference between the two neutrals causing the breaker to trip.
