What are RCDs?

RCDs stand for Residual Current Devices and are electrical devices designed to offer protection from lethal electric shocks by triggering an automatic electricity switch-off.  Thus, these life-saving devices prevent electrocution in the presence of a bare wire, overheating, or earth faults.

In the UK, RCDs are referred to as RCCBs or Residual-Current Circuit Breakers, while in the US and Canada they are known as GFCIs or Ground Fault Circuit Interrupters.

Types

RCDs are available in different types. These can be categorised into the following:

Fixed RCDs

These types of RCDs are typically used across both industrial and household applications. Installed within a fuse box, fixed RCDs are capable of protecting numerous circuits at the same time. When used as a part of the consumer power distribution unit, RCDs usually remain passive and help domestic appliances to normalise operations under restored circuit power. 

Socket-Outlet RCDs

These types of RCDs are designed to be used as an alternative to a standard socket outlet. Socket Outlet RCDs individually protect the user in direct contact with the equipment. 

Portable RCDs

Like socket-outlet RCDs, portable RCDs too offer individual protection. However, they can be plugged into any type of standard socket and are ideal for applications where outside power tools are used. 

How do RCDs work?

An RCD is installed in the circuits it is supposed to protect. It monitors the electric current to rapidly detect a circuit failure and identify when there are any disturbances in the flow of electricity. Upon detection of a fault, the RCD shuts down the circuit to protect the person who is handling the wires. When excessive current creates surges in the circuit, RCDs are combined with a fuse or MCB (miniature circuit breaker) to offer enhanced security.