To rcd or not to rcd, that is the question? Whether it is better to fit and forget, or to understand and correctly select and apply the correct device?

Residual current devices: the basics

What is an rcd?
A residual current device (rcd) is a product designed to provide protection against electrocution or fires by cutting off the flow of electricity automatically or actuating an alarm when it senses a leakage of electric current from a circuit.

How does it operate?
With an rcd, the live (brown) and neutral (blue) conductors pass through the core of a sensitive current transformer (see figure 1, above), the output of which is electrically connected to a tripping system.

In a healthy installation the current flows through the live and returns through the neutral conductor. Since these are equal and opposite, the core remains balanced.

When a leakage of electric current occurs (see figure 2), the live and neutral currents are no longer equal. This results in an output from the transformer, which is used to trip the rcd and disconnect the electrical supply.

Source

Electrical and Mechanical Contractor