To provide effective and reliable protection to the power system, a protective relay must have the following essential functional characteristics: Selective, Fast, Stable, Reliability, Sensitivity, Simple Construction and Installation Mechanism, and Cost-effective. The selected protection principle affects the operating speed of the protection, which has a significant im-pact on the harm caused by short circuits. For example, unselective protection operation during a medium voltage network fault will cause an outage for an unnecessarily large number of consumers. It sends a signal to turn on the alarm or indicator or trip a circuit breaker to separate the faulty part from the healthy section. The primary. Protective relays and devices have been developed over 100 years ago to provide “last line” of defense for the electrical systems. The protective philosophy is fundamentally grounded on the understanding that faults or abnormal operating. Such essential qualities of protective relaying are, Reliability A protective relaying should be reliable, it is its basic quality. There are various components which go into the operation before a relay.
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