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, within a certain range, constantly monitors the equipment and lines of the operating power system for any abnormal or accident conditions, and can issue trip commands or signals. It studies power system faults and abnormal conditions that endanger safe operation, and explores countermeasures as anti-accident automation measures. Because in its development process, relay protection mainly used contact relays to protect the power system and its components (generators, transformers, transmission lines, busbars, etc.) from damage, it is thus called relay protection.
(1) Speed: To limit the expansion of faults, reduce equipment damage, and improve system stability, faults must be cleared quickly. The fault clearing time is from the occurrence to the arc extinction after tripping.
(2) Reliability: Relay protection devices should always be in a perfect and flexible working state. Once a fault occurs, the protection device should act reliably and promptly, 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.
