What are the models of relay protection devices

Relay protection devices are categorized by function, mechanism, and standard device numbers, covering overcurrent, voltage, distance, differential, and specialized relays. Classification by Function and MechanismProtective relays are automatic devices that detect abnormal conditions in electrical circuits and initiate actions to isolate faults, ensuring system safety and reliability. They are classified by: Mechanism: Electromagnetic, static, or digital/numerical relays.

Function: Overcurrent, overvoltage, undervoltage, differential, distance, directional, and specialized relays. Time Characteristics: Instantaneous, definite time, or inverse time relays. Common ANSI/IEEE Standard Device NumbersIn North America, protective relays are identified using ANSI/IEEE C37.

2 standard device numbers, sometimes with suffixes to indicate specific applications: 50 – Instantaneous Overcurrent Relay51 – AC Time Overcurrent Relay50N – Instantaneous Neutral Overcurrent Relay51N – Neutral Time Overcurrent Relay27 – Undervoltage Relay59 – Overvoltage Relay59B – Bus Overvoltage Relay21 – Distance Relay87 – Differential Relay86 – Lockout Relay (e.g., 86T for transformer)46 – Negative Sequence Overcurrent Relay32 – Directional Power Relay78 – Phase Angle Measuring Relay79 – AC Reclosing Relay Suffixes like T (transformer), B (bus), or G (generator) specify the application.

Types of Protective Relays

Protective relays can also be categorized by operating principle: Electromechanical Relays: Operate using coils and moving contacts; traditional and robust. Static Relays: Use electronic circuits for faster response and higher accuracy.

Digital/

Numerical Relays: Microprocessor-based, combining protection, metering, and control in one device; programmable for multiple functions.

Manufacturer Models and Selection

Major manufacturers provide relay selection tables to match system requirements with specific models: ABB: RET, REF, and REJ series for overcurrent, distance, and differential protection. Siemens: 7SR, 7UT, and 7SD series for numerical protection. Schneider Electric: Sepam series for multifunction protection.

G

E Grid Solutions: Multilin series (e.g., 850, 869, 889) for digital protection.

SE

L (Schweitzer Engineering Laboratories): SEL-351, SEL-751, SEL-700G for various applications. These models integrate protection, control, and metering, often supporting communication protocols like IEC 61850 for modern substations.

Summary

A complete list of relay protection devices includes: ANSI/IEEE device numbers for standard identification. Relay types by mechanism and function. Manufacturer-specific models for practical application.

This framework allows engineers to select, coordinate, and implement protective relays for power systems, ensuring both primary and backup protection.