ABB REX521 Numerical Feeder Protection Relay

Availability: 10 left in stock

ABB REX521 Overcurrent and Earth-Fault Protection Relay Configured for feeder fault detection and continuous line monitoring in distribution networks, the...

SKU: REX521

Manufacturer: ABB
Product No.: REX521
Product Type: Protection Relays
Product Origin: Switzerland
Payment:T/T, Western Union
Weight: 2500g
Shipping port: Xiamen
Warranty: 12 months

Description Reviews

ABB REX521 Overcurrent and Earth-Fault Protection Relay

Configured for feeder fault detection and continuous line monitoring in distribution networks, the ABB REX521 (REX521 Protection Relay) provides direct physical/electrical execution. The unit processes multi-function overcurrent, earth-fault, thermal overload, and phase imbalance protection algorithms across medium-voltage utility and industrial platforms. Operating across 1 A or 5 A selectable current inputs with a 24-250 VDC or 48-240 VAC auxiliary power supply, the relay executes high-speed fault isolation and event recording.

Hardware Specifications

Parameter	Specification
Model	REX521
Brand	ABB
Origin	Sweden / Finland
Weight	2.5 kg
Dimensions	160 mm x 180 mm x 200 mm
Operating Temp	-25 to +70 deg C
Power Consumption	Universal Auxiliary Input: 24-250 VDC or 48-240 VAC
Protection Logic	Non-directional/directional overcurrent, earth-fault, thermal overload, phase imbalance
Rated Current Input	1 A or 5 A (hardware/software selectable)
Rated Voltage Input	Standard 100 V / 110 VAC
Nominal Frequency	50 / 60 Hz
Digital I/O	Multiple programmable binary inputs and outputs
Field Protocols	Modbus RTU/TCP, IEC 60870-5-103, SPA bus
Ingress Protection	IP20 (Rear), up to IP54 (Front panel with protective cover)

Backplane Bus Communication Velocity and Deterministic Networks

Industrial substation platforms rely on deterministic protocol execution to ensure fast trip execution and reliable telemetry. The ABB REX521 integrates Modbus RTU/TCP, IEC 60870-5-103, and SPA bus protocol stacks across dedicated serial and Ethernet physical layers. Network deterministic throughput guarantees low protocol latency during fault events, allowing real-time disturbance records and event logs (up to 200 events) to transmit to upper-level SCADA systems without impairing backplane protection logic processing.

Frequently Asked Questions

Q: How are current inputs configured on the ABB REX521 hardware? A: CT secondary circuits connect to selectable terminals supporting either 1 A or 5 A nominal rated current inputs via hardware tap or software configuration.

Q: What data recording capabilities are available on the relay during a power system fault? A: The relay includes an integrated disturbance recorder along with non-volatile event logging memory capable of storing up to 200 sequential events.

Q: Does the unit support hot-swapping or online withdrawal during operation?

A: Terminal block connections must be de-energized and current transformer secondaries shorted before removing or replacing the panel-mounted unit to prevent dangerous overvoltages.

Field Installation Guidelines

Cut out panel dimensions to fit the 160 mm x 180 mm frame and mount the unit flush using standard panel clamps.
Verify that CT secondary circuits are shorted prior to connecting 1 A or 5 A current input wiring to the terminal blocks.
Wire auxiliary power supply connections to the universal input terminals accepting 24-250 VDC or 48-240 VAC.
Connect communication lines (Modbus, IEC 60870-5-103, or SPA bus) using shielded twisted-pair cables isolated from high-voltage primary conductors.
Connect the rear protective earthing terminal directly to the main station ground bar using a low-impedance copper strap.

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