Basics of Relay Protection

The Role of Relay Protection

Relay protection is an essential measure for detecting faults or anomalies in the power system, thereby issuing alarm signals or directly isolating and cutting off the faulty parts. Its primary functions include:12

Quickly Disconnect from Fault: In the event of a fault in the power grid that is sufficient to damage equipment or threaten the safety of the grid, quickly disconnect the protected equipment to prevent the fault from escalating.

Timely Alarm Signals: The system can promptly issue alarm signals for abnormal operation of the power grid and certain equipment's unusual status, enabling swift response and restoration to normal operation.

Achieving automation and remote control of the power system: as well as automatic control in industrial production, such as automatic circuit breaker closing; automatic engagement of standby power sources; remote control, remote sensing, and remote signaling, etc.

The application of relay protection devices is very extensive, including but not limited to high-voltage power supply systems in factories and enterprises, substation, etc., used for line protection of high-voltage power supply systems, main transformer protection, capacitor protection, and more. With the rapid development of relay protection technology, micro-computer protection devices are gradually being introduced, enhancing the reliability of protection.

The basic concept and function of relay protection are based on the physical quantities that constitute relay protection action, which are the changes in electrical quantities (current, voltage, power, frequency, etc.) during short circuits or abnormalities in the components of an electrical power system. Its fundamental task is to, in the event of faults or abnormalities in the power system, automatically disconnect the faulty equipment from the system within a short time and small area, or send signals for the on-duty personnel to eliminate the root cause of the abnormal condition, in order to avoid or mitigate equipment damage and reduce the impact on power supply to adjacent areas.