Siemens Reyrolle 5 7SR5121 Overcurrent & Feeder Protection Numerical Relay

The Siemens Reyrolle 5 7SR5121 is a directional time-overcurrent protection relay designed for advanced feeder protection applications. It provides comprehensive protection functions along with IEC 61850 Ethernet communication support for modern digital substations.

The device is part of the Reyrolle 7SR51 family and supports enhanced communication and cybersecurity features. It includes a wide range of protection functions and is suitable for applications requiring directional protection with advanced features such as fault locator, synchrocheck, and load blinder.

The relay features a user-friendly interface with integrated communication ports and flexible hardware configurations, making it suitable for complex and interconnected power systems.

Siemens Reyrolle 5 7SR5121 Inputs and Outputs

5 CT + 4 VT + 22 BI + 15 BO (including high-speed outputs)
5 CT + 4 VT + 37 BI + 18 BO
5 CT + 4 VT + 37 BI + 21 BO (including 3 HSBO, Arc Flash Detector inputs)

Communication

Standard interfaces include:

• 1 × USB (front)
• RS485 (rear)
• 2 × RJ45 or optical Ethernet ports

Housing

Available in S8 / S12 enclosure variants depending on configuration.

Reyrolle 7SR5121 Numerical Relay Functions

Standard Functionality

• 37 / 37G Undercurrent protection
• 46 Negative sequence overcurrent protection
• 46BC Broken conductor detection
• 49 Thermal overload protection
• 50 Instantaneous overcurrent
• 51 Time delayed overcurrent

Advanced Directional Functionality (7SR5121)

• 21FL Fault locator
• 21LB Load blinder
• 25 Synchrocheck – synchronizing function
• 27 Undervoltage protection
• 32 Power protection
• 47 Sequence overvoltage protection
• 51V Voltage-dependent overcurrent
• 55 Power factor
• 59 Overvoltage protection\
• 60VTS VT supervision
• 67 Directional overcurrent
• 81 Frequency protection
• 81R Rate of change of frequency

Monitoring Functions

• Measurement of current and voltage parameters
• Power system monitoring and fault analysis

Communication

• IEC 60870-5-103
• MODBUS-RTU
• DNP 3.0
• IEC 61850

Applications

• Directional overcurrent protection for interconnected networks
• Feeder protection in medium-voltage substations
• Backup protection for lines, transformers, and generators
• Suitable for systems requiring advanced functions like synchrocheck and fault location

Benefits

• Advanced directional protection with extended functionality
• Flexible hardware configurations for different applications
• Integrated communication for digital substations
• Reliable performance with proven protection algorithms