What Is Relay Protection?
Relay protection is a system that automatically detects and isolates faults in electric power systems to protect equipment and prevent damage to the system. Its main function is to cut off the problematic part of the power system in time when the power system fails, so as to protect the safe and stable operation of the power system.

How Protection Relay Works
A protection relay detects abnormal conditions (such as overcurrent, overvoltage, or under-frequency) in an electrical system, and initiates a trip signal to isolate the affected equipment from the system. It does this by monitoring electrical quantities, comparing them to preset thresholds, and then activating the trip signal when the threshold is exceeded.

Protection Relay Types

The protection relay is an important device in the power system, mainly used to protect the equipment and lines of the power system, prevent overload, short circuit, grounding, and other faults of power equipment, and ensure the safe and reliable operation of the power system. According to the function and application occasion of the protective relay, it can be divided into the following types:

1. Overcurrent protection relay: It is mainly used to protect equipment such as lines and transformers in the power system. When the current exceeds the set value, the protection relay will act in time to cut off the circuit and prevent equipment from being overloaded and burned.
2. Trip protection relay: It is mainly used to protect the switching equipment in the power system. When a short circuit or fault occurs in the circuit, the protection relay will act in time to cut off the circuit and prevent the accident from expanding.
3. Grounding protection relay: It is mainly used to protect the safety of equipment and personnel in the power system. When the circuit is grounded, the protection relay will act in time to cut off the circuit and prevent electric shock accidents.
4. Overvoltage protection relay: It is mainly used to protect the equipment in the power system. When the voltage exceeds the set value, the protection relay will act in time to cut off the circuit and prevent the equipment from being burned due to overvoltage.
5. Under voltage protection relay: It is mainly used to protect the equipment in the power system. When the voltage is lower than the set value, the protection relay will act in time to cut off the circuit and prevent the equipment from being damaged due to under voltage.
6. Under frequency protection relay: It is mainly used to protect the generator in the power system. When the grid frequency is lower than the set value, the protection relay will act in time to cut off the connection between the generator and the grid to prevent the generator from being overloaded and damaged.
7. Over-frequency protection relay: It is mainly used to protect the equipment in the power system. When the grid frequency exceeds the set value, the protection relay will act in time to cut off the circuit and prevent equipment from being overloaded and burned.

Blue Jay, a manufacturer of automatic protection relays, mainly provide arc flash relay, motor protection relay, switchgear monitor like residual current monitor, partial discharge monitor, etc, industrial temperature and humidity controller, and high voltage detector.

Protection Relay Function
Relay protection usually uses signals in the power system as input to process and judge these signals. When a fault occurs in the power system, relay protection can respond quickly and take appropriate protection measures. The realization of the relay protection function is usually achieved by using advanced electronic equipment such as microprocessors, digital signal processors, and digital signal controllers. The main functions of relay protection include:

1. Over-current protection: When the current exceeds the rated value, the protection device will perform protection operations in time to avoid failure of the power system due to excessive current.
2. Overvoltage protection: When the voltage exceeds the rated value, the protection device will perform protection operations in time to avoid failure of the power system due to excessive voltage.
3. Under-voltage protection: When the voltage is lower than the rated value, the protection device will perform protection operation in time to avoid failure of the power system due to low voltage.
4. Grounding protection: When a grounding fault occurs in the power system, the protection device will perform protection operations in time to prevent the power system from malfunctioning due to the grounding fault.
5. Overload protection: When the load in the power system exceeds the rated value, the protection device will perform protection operations in time to avoid failure of the power system due to excessive load.
6. Short-circuit protection: When a short-circuit occurs in the power system, the protection device will perform protection operations in time to avoid failure of the power system due to short-circuit faults.

The relay protection function is a key component of the safe and stable operation of the power system, and the correct selection and configuration of the protection device is crucial to the reliability and safety of the power system.