Description

The ABB REA101-AAA is a high-sensitivity residual current(earth fault)relay designed to detect dangerous ground leakage currents in low-voltage electrical installations.As part of ABB’s Relion®protection portfolio,this compact,DIN rail-mounted device works in conjunction with toroidal current transformers(CTs)to monitor the vector sum of phase and neutral currents.If an imbalance exceeds the preset threshold—indicating insulation failure,equipment fault,or risk of electric shock—the REA101-AAA triggers a trip signal to disconnect power or activate an alarm,thereby preventing fire hazards,equipment damage,and personal injury.

Engineered for simplicity and reliability,the REA101-AAA supports adjustable sensitivity(from 30 mA to 30 A)and time delay settings,making it suitable for both life safety(high sensitivity)and equipment protection(lower sensitivity)applications across industrial,commercial,and infrastructure sectors.

Application Scenarios

In a European hospital’s critical care wing,repeated nuisance tripping of standard RCDs disrupted sensitive medical equipment.Engineers replaced them with a coordinated system using ABB REA101-AAA relays paired with 630 A toroid CTs on each sub-distribution board.They set the sensitivity to 300 mA with a 100 ms intentional delay—high enough to ignore harmless capacitive leakage from MRI machines and ventilators,yet fast enough to clear dangerous faults before they escalated.Over 18 months,the system eliminated unplanned outages while maintaining full compliance with IEC 60364-4-41 for patient areas.During one incident,a faulty infusion pump developed a 450 mA ground fault;the REA101-AAA isolated only its circuit within 120 ms—protecting patients without affecting neighboring beds.For facility managers,the relay became a silent guardian of both continuity and safety.

This balance of selectivity and responsiveness exemplifies why the REA101-AAA is trusted where lives and uptime are non-negotiable.

Parameter

Main Parameters Value/Description

Product Model REA101-AAA

Manufacturer ABB Ltd.

Product Category Residual Current/Earth Fault Relay

Operating Principle Detects imbalance via external toroidal CT(not included)

Adjustable Sensitivity Range 30 mA,100 mA,300 mA,500 mA,1 A,3 A,5 A,10 A,30 A

Time Delay Settings Instantaneous or adjustable(0.1 s to 1.0 s)

Supply Voltage 24–230 V AC/DC(universal auto-ranging)

Output Contacts 1 x SPDT(changeover)relay:5 A 250 V AC

Standards Compliance IEC 60755,IEC 60255,EN 50178,CE,UL 508

Mounting 35 mm DIN rail(EN 60715)

Operating Temperature-25°C to+55°C

Degree of Protection IP20(for installation in enclosed panels)

Dimensions 22.5 mm(W)×90 mm(H)×100 mm(D)

Key Feature Test button,LED indicators(power,trip,fault),easy front-access calibration

Technical Principles and Innovative Values

Innovation Point 1:Multi-Range Selectivity–The REA101-AAA’s wide sensitivity range allows a single device to serve both personnel protection(30–300 mA)and fire prevention/equipment protection(300 mA–30 A),reducing inventory complexity.

Innovation Point 2:Immunity to Transients–Advanced filtering algorithms reject high-frequency noise from VFDs,SMPS,and switching loads—preventing false trips in modern electrical environments rich in harmonics.

Innovation Point 3:Universal Power Supply–Operates on any common control voltage(24 VDC to 230 VAC),eliminating the need for auxiliary power supplies in most panels.

Innovation Point 4:Diagnostic Clarity–Bright LEDs instantly show operational status:green=healthy,red=tripped,flashing=self-test active—accelerating troubleshooting during maintenance.

Application Cases and Industry Value

At a U.S.data center,a server rack PDU developed insulation degradation due to condensation,causing intermittent 200 mA leakage.Standard breakers didn’t respond,but thermal buildup posed a fire risk.After installing REA101-AAA relays on all critical PDUs(set to 300 mA,200 ms delay),the system flagged the anomaly during routine monitoring.The faulty PDU was replaced during scheduled maintenance—averting a potential fire that could have cost millions in downtime.The facility now mandates REA101-AAA on all new IT power circuits.

In another case,a food processing plant used the REA101-AAA to protect washdown-area motors.Despite frequent high-moisture exposure,the relay’s robust design ensured no corrosion-related failures over five years—proving its resilience in harsh CIP(Clean-in-Place)environments.

Related Product Combination Solutions

ABB TAxx Toroid CTs(e.g.,TA75,TA120):External current transformers sized to cable bundle diameter—essential for REA101-AAA operation.

ABB Tmax XT Circuit Breakers:Pair with REA101-AAA for shunt-trip disconnection upon earth fault detection.

REA102-AAA:Enhanced version with two independent thresholds(alarm+trip)—ideal for predictive maintenance.

ABB Ekip Trip Units:For integration into molded-case breakers with built-in ground fault protection.

ABB Ability™Monitoring:Connect REA101-AAA contacts to SCADA for remote fault logging and asset health tracking.

Phoenix Contact RELays:Compatible interface modules for PLC alarm integration.

ABB RES010:Test resistor module—simplifies periodic functional testing of the REA101-AAA loop.

ABB Distribution Boards(e.g.,Megamax):Pre-engineered panels with REA101-AAA pre-installed for rapid deployment.

Installation,Maintenance,and Full-Cycle Support

Installation requires mounting the REA101-AAA on a DIN rail,connecting the supply voltage,wiring the toroid CT secondary leads to the input terminals,and linking the output contact to a shunt coil or alarm circuit.Use shielded twisted-pair cable for CT connections(<10 m recommended).Set sensitivity and delay using the front rotary switches—no software needed.

Maintenance involves monthly pressing of the TEST button to verify functionality and annual inspection of CT integrity and terminal tightness.The relay requires no calibration under normal conditions.

All ABB REA101-AAA units we supply are genuine ABB products with full traceability,CE/UL marks,and original documentation.Backed by a 24-month warranty and supported by ABB-certified engineers,we provide application design assistance,coordination studies,and replacement guidance.Contact us today to enhance your electrical safety infrastructure with proven,reliable ground fault protection.

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