ABB REJ 511 Earth-Fault Protection Relay

The ABB REJ 511, also cataloged as the REJ 511 Earth-Fault Protection Relay, operates as a dedicated secondary relay component for measuring neutral current, executing fault isolation, and providing disturbance recording across electrical distribution networks.

Suffix Breakdown & Model Matrix

• REJ 511: Base designation for the ABB numerical earth-fault protection relay platform.
• Hardware Configuration: Standard modular enclosure profile equipped with internal digital measurement cores and configurable output contact matrices.

Hardware Specifications

System Integration and Communication Architecture

• Backplane Bus Communication Velocity: Executes deterministic internal data routing across internal microprocessor buses to maintain fast earth-fault threshold tripping calculations.
• Profinet / EtherNet/IP Deterministic Networks: Supports standardized auxiliary communication protocols for local event extraction, disturbance record downloading, and parameter configuration.
• I/O Density Scaling: Integrates configurable output contact matrices routing start and trip signals from independent protection stages to desired relay output terminals.
• Firmware Flash Compatibility: Permits internal self-supervision and parameter adjustments via protected communication interfaces without altering physical switchgear wiring.

Frequently Asked Questions (FAQ)

• Q: Can the internal power supply or relay modules be replaced while the switchgear panel is energized?

  A: No, module replacement requires de-energizing the unit and isolating connected current transformer secondary circuits to prevent open-circuit high-voltage hazards.

• Q: What protection stages are included in the earth-fault unit?

  A: The unit includes a low-set stage with definite time or IDMT characteristics and a high-set stage with instantaneous or definite time characteristics.

• Q: Does the relay support circuit-breaker failure protection?

  A: Yes, it incorporates an integrated circuit-breaker failure protection unit alongside a disturbance recorder and continuous self-supervision.

Field Installation Guidelines

• Ensure the relay case earth terminal is connected directly to the switchgear ground bus using a low-impedance conductor.
• Verify that auxiliary supply voltage levels match the rated input range prior to energizing the unit.
• Terminate all current transformer secondary leads securely to the rear terminal blocks, ensuring proper shorting links are removed only after final connection.
• Maintain clear vertical clearance around the compact enclosure to ensure proper thermal dissipation across the specified operating temperature range.