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ABB REX-521 Feeder Protection Relay 

1. Key Parameters

• Product Model: REX-521
• Product Series: ABB REX-Series Industrial Feeder Protection Relays (LV/MV Feeder Circuit Protection)
• Core Function: Overcurrent/short-circuit/earth fault protection; load monitoring; fault recording; remote control; compatible with Modbus/IEC 61850.

2. Core Features

• Feeder-Specific Protection: Integrates overcurrent, short-circuit, and earth fault protection—targeting common feeder faults to minimize outage scope.
• High-Precision Measurement: ±0.5% current measurement accuracy ensures reliable fault detection and load monitoring.
• Flexible Communication: Supports Modbus for basic remote monitoring, or optional IEC 61850 for smart grid integration.
• Industrial Durability: -25℃~+70℃ operating range and IP40 protection resist dust, temperature fluctuations, and electrical interference in distribution cabinets.

3. Application Fields

• Factory Distribution: Protects 0.4kV~10kV feeders supplying power to production lines, workshops, or auxiliary equipment.
• Urban Power Grids: Guards MV/LV feeders in residential/commercial areas, preventing fault spread to other users.
• Industrial Auxiliary Systems: Secures feeders for pumps, fans, or transformers in power plants, refineries, or steel mills.

4. Precautions

• Compatibility: Configure CT ratio (5A/1A) and power supply (DC/AC) to match system parameters; use optional IEC 61850 only for smart grid setups.
• Installation: Follow LV/MV distribution cabinet wiring standards; separate control cables from high-voltage power cables to reduce EMI.
• Maintenance: Calibrate protection parameters annually; back up fault records quarterly; update firmware per ABB technical notices.
• Spare Parts: Use genuine ABB REX-521 units—non-genuine relays may miss faults or trigger false tripping, leading to feeder downtime.

The structure and details of the product：

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