The NMS system configures a default digital relay using the Protection Scheme Default Relay configuration rule. This tells the NMS which digital relay to use as the default if one of the relays has been inhibited and the NMS system attempts to set that relay. By default relay 4 is set to the default relay.

For example, a switch is moved to a feeder through switching that requires the protection schemes to be moved to relay 1. Relay 1 is currently inhibited so the system sends a control to set relay 4 on instead. Some time later the inhibit is removed from relay 1 and the NMS sends a control to set relay 1 on.