Once a protection relay detects a fault, it will operate automatically and will close down the breaker's trip circuit. This way the faulty circuit will be disconnected from the system and the circuit breaker will be open. It functions as a watchdog by constantly surveying multiple system components including voltage, current, frequency, and phase angle. It. Lock out relay is an electromechanical relay which latches its output contact. These relay have two types of coils: operating and resetting. The objective of relay protection is to quickly isolate a faulty section from both ends so that the rest of the system can function satisfactorily. The functional requirements of the relay: The most important requisite of the protective relay is reliability since they supervise the circuit for a. Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems. 1-1-4 Exporting to Tropical Zones Use the following types of Relays if they are to be exported to tropical zones.