ABB REX521 Feeder Protection Relay

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1. Product Overview

The ABB REX521 is a feeder protection relay designed for medium and low-voltage distribution systems, providing protection against overcurrent, short-circuit, earth faults, and voltage anomalies.
REX521 offers reliable digital protection, measurement, monitoring, and communication functions, supporting IEC 61850, Modbus, and other industrial communication protocols for intelligent distribution management.

2. Main Technical Specifications (Typical)

• Model: REX521

• Product Type: Feeder Protection Relay

• Rated Voltage: AC 100–240 V or DC 24–60 V

• Protection Functions: Overcurrent, overload, short-circuit, earth fault, undervoltage, overvoltage

• Measurement Functions: Three-phase current, voltage, active/reactive power, power factor, frequency

• Communication Interfaces: Modbus RTU, IEC 61850, Profibus DP (optional)

• Inputs/Outputs: Digital I/O terminals

• Operating Temperature Range: -25 ℃ to +70 ℃

• Mounting: Panel or DIN rail installation

• Display: LCD screen with LED indicators

• Dimensions: 144 × 144 × 90 mm (typical panel mount)

3. Key Advantages and Features

1. Comprehensive Feeder Protection

   • Supports overcurrent, earth fault, short-circuit, undervoltage/overvoltage protection

   • Enhances system safety

2. Intelligent Monitoring and Measurement

   • Real-time measurement of current, voltage, power, and power factor

   • Event logging and fault analysis

3. Flexible Communication

   • Supports Modbus, IEC 61850, and other industrial protocols

   • Easy integration with SCADA and smart distribution systems

4. High Reliability and Durability

   • Industrial-grade design, vibration resistant, high-temperature tolerant

   • LCD display and LED indicators for easy monitoring and maintenance

5. Easy Installation and Operation

   • Panel or DIN rail mounting

   • Simple configuration and programming, supports remote settings

4. Typical Applications

• Feeder protection in medium and low-voltage distribution systems

• Industrial plants, commercial buildings, and infrastructure distribution networks

• Power systems in mining, petrochemical, and metallurgical plants

• Smart grids and SCADA system integration

• Backup power and generator feeder protection

5. Installation and Maintenance Notes

1. Verify Voltage Rating and Wiring

   • Ensure input voltage matches relay rated voltage

   • Connect current and voltage transformers according to instructions

2. Power-Off Before Installation

   • Disconnect power before installing or maintaining the relay

3. Environmental Conditions

   • Avoid high temperature, humidity, and corrosive environments

   • Ensure proper ventilation in the cabinet

4. Periodic Inspection

   • Check LCD display and LED indicators

   • Verify protection settings and relay operation

5. Communication and Monitoring

   • Ensure network protocols match when configuring communication

   • Regularly back up protection configuration parameters