In power system networks, protection has to be designed such that protective relays isolate the faulted portion of the network, to prevent equipment damage, injury to operators and to ensure minimum system disruption enabling continuity of service to healthy portion of the network.
Relay coordination is used to achieve proper fault identification and fault clearance sequence. These relays must be able to differentiate between the normal operating currents that including short time over currents that may appear due to certain equipment normal operation such as motor starting currents, Transformer inrush currents and sustained overcurrent due to fault conditions. During fault conditions, these relays must operate quickly so as to isolate the faulted part of the network only and allowing for continued operation of the healthy circuits. Know More