An RCD (Residual Current Device) is a life-saving device which is designed to prevent you getting a fatal electric shock if you touch something live, such as a bare wire - a level of personal protection that ordinary fuses and circuit breakers cannot provide. Sometimes people think that an RCD was just some sort of safety plug that you used with your lawn mower and don’t understand that there are a number of different types of RCD. Customers sometimes don't realise just how important these devices are. They could save your life or prevent serious injury.
These are installed in your consumer unit (fuse board) and this provides the best protection as it covers all sockets and appliances on the circuit connected to it.
These replace standard sockets and protect only a person in contact with equipment plugged into the socket.
Plug in RCD's are plugged into any socket and then an appliance can be plugged into the portable RCD to provide protection. This is the one I had come across as they are most commonly used for appliances used outdoors such as lawn mowers.
If your consumer unit was installed before 2008 there is a good chance that your consumer unit does not have the correct RCD protection.
Check out our "Should I change my Fuseboard?" page.
For further information on electrical safety, RCD's and Home Electrics please visit The Electrical Safety First Website