The relay protection major includes
The main types of protective relays include overcurrent relays, differential relays, distance relays, earth fault relays, and directional relays. Protective relays and devices have been developed over 100 years ago to provide "lastline"of defense for the electrical systems. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. The components used in the power system are usually dimensioned to withstand a short circuit current for one or three seconds but power system stability during short circuit current may be endangered already after 200ms. It functions as a watchdog by constantly surveying multiple system components including voltage, current, frequency, and phase angle.
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