There are two types of RCD’s: Active & Passive, also termed Latching & Non-latching.
Both types are accepted by British Standards and it is up to the user to choose the type of RCD that is most suitable for their application.
Active (Non-latching) - RCD’s switch off if power to them is turned off. Every time the appliance is turned off, the RCD will trip & have to be reset by going to the socket.
Passive (latching) - RCD’s “remember” what state they were in prior to the power being switched off.
On the resumption of the power, the power will then continue to be supplied to the appliance, & the RCD does not need to be reset.
Ryness Electrical Supplies Ltd, Unit 5B Sovereign Way, Botany Trading Estate, Tonbridge, Kent, TN9 1RH - email@example.com