ABB REA101 Neutral Voltage Displacement Relay

ABB REA101 Neutral Voltage Displacement Relay – Precision Earth Fault Detection

The ABB REA101 is a specialized neutral voltage displacement (59N) protection relay engineered for sensitive earth fault detection in ungrounded and high-impedance grounded electrical distribution systems. As part of ABB's trusted Relion® protection relay family, the REA101 continuously monitors zero-sequence voltage to identify insulation failures, ground faults, and system imbalances before they escalate into catastrophic equipment damage or safety hazards.

Core Technical Specifications

• Protection Function: Neutral voltage displacement (59N) with adjustable pickup threshold
• Voltage Measurement: Zero-sequence voltage via broken-delta VT connection
• Pickup Range: 1-100% of rated voltage (configurable)
• Time Delay: Definite time (0.1-300 seconds) or inverse time characteristics
• Binary Inputs: 4 configurable inputs for external control signals
• Output Contacts: 4 relay outputs (alarm/trip functions, Form C contacts)
• Communication: RS-232 serial interface for configuration and monitoring
• Optional Interface: Fiber optic communication for EMI-immune data transmission
• Power Supply: Universal 24-265 VAC/DC input
• Operating Temperature: -25°C to +55°C ambient range
• Mounting: 19" rack (4U) or panel mount configuration
• Dimensions: 177 mm (H) × 177 mm (W) × 144 mm (D)
• Protection Rating: IP54 front panel, IP20 rear terminals
• Standards: IEC 60255, ANSI/IEEE C37.2, CE, UL, CSA certified

Protection Principle & Operation

In ungrounded or high-impedance grounded systems, phase-to-ground faults do not produce significant fault currents, making traditional overcurrent protection ineffective. The REA101 solves this challenge by monitoring the neutral point voltage derived from a broken-delta connected voltage transformer (VT) secondary. When a ground fault occurs, the system's neutral point shifts from ground potential, creating a measurable zero-sequence voltage that the REA101 detects with high sensitivity.

The relay's dual-stage protection scheme provides both alarm (low-level faults) and trip (critical faults) outputs, enabling operators to investigate minor insulation degradation before mandatory system shutdown. Adjustable time delays prevent nuisance tripping from transient voltage spikes while ensuring rapid response to sustained ground faults.

Application Scenarios & Industrial Solutions

Mining & Quarrying Operations: Deploy in underground mine power distribution where ungrounded systems are mandated for personnel safety. The REA101's sensitive ground fault detection enables continuous operation while alerting maintenance teams to developing insulation failures in harsh, moisture-laden environments.

Petrochemical Facilities: Protect critical process equipment in hazardous area electrical systems where ungrounded distribution minimizes arc flash energy during ground faults. The relay's alarm function allows planned shutdowns for fault investigation, preventing uncontrolled process interruptions.

Marine & Offshore Platforms: Monitor shipboard and offshore platform power systems where saltwater exposure accelerates insulation degradation. Early detection of ground faults prevents cascading failures in isolated power networks with limited redundancy.

Industrial Manufacturing: Safeguard resistance-grounded medium-voltage systems in automotive, steel, and paper mills. The REA101 coordinates with downstream protection devices to isolate faulted feeders while maintaining service to healthy circuits, maximizing production uptime.

Advanced Features & Capabilities

• Directional Sensitivity: Optional directional element distinguishes forward/reverse ground faults in multi-source systems
• Harmonic Filtering: Third-harmonic rejection prevents false tripping from capacitive charging currents
• Event Recording: Time-stamped fault logs with pre-fault and post-fault voltage waveforms
• Self-Diagnostics: Continuous monitoring of VT circuits, power supply, and internal circuitry
• Programmable Logic: Customizable trip/alarm schemes via configuration software
• Modbus Integration: Optional protocol support for SCADA system connectivity

Installation & Configuration Guidelines

VT Connection: Connect the relay to a broken-delta (open-delta) secondary winding of the system voltage transformers. The broken-delta configuration produces zero output voltage under balanced conditions and develops voltage proportional to 3V₀ (three times zero-sequence voltage) during ground faults.

Pickup Setting: Set the voltage pickup threshold based on system capacitance and grounding impedance. Typical settings range from 5-15% of rated voltage for high-impedance grounded systems and 20-50% for ungrounded systems to ensure sensitivity while avoiding false trips from normal voltage imbalance.

Time Delay Coordination: Coordinate time delays with downstream protection devices to achieve selective tripping. Use definite time delays for simple radial systems or inverse time characteristics for complex networks requiring grading with multiple protection zones.

Related Protection & Monitoring Products

System Integration Benefits

• ✓ Relion Compatibility: Seamless integration with ABB Relion protection and control ecosystem
• ✓ Reduced Downtime: Early fault detection enables proactive maintenance scheduling
• ✓ Personnel Safety: Rapid ground fault isolation minimizes electric shock and arc flash hazards
• ✓ Asset Protection: Prevents insulation damage escalation and equipment burnout
• ✓ Regulatory Compliance: Meets NEC, IEC, and industry-specific grounding standards

Technical Support & Documentation

Complete technical documentation includes installation manuals, application guides, wiring diagrams, and configuration software. ABB's global support network provides application engineering assistance for protection coordination studies, settings calculations, and system commissioning.

Quality Assurance & Certifications

The REA101 undergoes rigorous factory testing including high-voltage dielectric tests, burden verification, and functional validation per IEC 60255 standards. Type-tested for seismic qualification (IEEE 693) and electromagnetic compatibility (IEC 61000-4 series) to ensure reliable operation in demanding industrial environments.

Order Information

• Model Number: REA101
• Availability: In stock – ready to ship
• Lead Time: 3-5 business days (standard shipping)
• Warranty: Standard manufacturer warranty included
• Package Contents: Relay module, mounting hardware, configuration cable, technical documentation
• Minimum Order: 1 unit

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