An examination of RCD performance during system disturbances (and other relays)

There are stringent requirements associated with protection equipment, such as residual current devices (RCDs) and protection relays. Most requirements deal exclusively with only pure sinusoidal waveforms while in reality the supply may contain harmonics. The protection equipment is thus subject to a nonsinusoidal waveform and its behaviour under such conditions is not well documented. The authors review the results of the simulation, mathematical modelling and experimental work on RCDs and protection relays, the electromechanical instantaneous overcurrent relay and the electromechanical time overcurrent relay, used on nonsinusoidal waveforms carried out at Aston University