It is an important measure to detect faults or abnormal conditions in the power system, thereby issuing alarm signals, or directly isolating and removing the faulty part. It is also an automatic device that monitors equipment and lines in the operating power system within a certain range for any abnormalities or accidents, and can issue trip commands or signals. It studies power system faults and abnormal conditions that endanger safe operation, and explores countermeasures for anti-accident automation. Because in its development process, relay protection was mainly used to protect the power system and its components (generators, transformers, transmission lines, busbars, etc.) from damage using contact relays, it is still commonly referred to as relay protection.
(1) Speed: To limit the expansion of faults, reduce equipment damage, and improve system stability, faults must be quickly cleared. The fault clearing time is from the occurrence to the tripping and arc extinction.
(2) Reliability: Relay protection devices should always be in a perfect and flexible working state. Once a fault occurs, the protection device should act promptly and reliably, and should not misoperate or refuse to operate due to its own defects.
(3) Selectivity: The protection device should only act on the faulty equipment, minimizing the scope of power outage to ensure the normal operation of other equipment.
(4) Sensitivity: The protection device should have sufficient response capability to various faults.
