ABB REJ603 – Feeder Overcurrent & Earth-Fault Protection Relay for MV distribution

The ABB REJ603 is a compact protection IED designed for medium-voltage feeders that need reliable, non‑directional overcurrent (50/51) and earth‑fault (50N/51N) protection. From my experience, it fits nicely in ring‑main units, compact substations, and industrial switchboards where you mainly want fast, dependable tripping, clear event logs, and straightforward integration to existing SCADA.
One thing I appreciate is how it typically handles both 1 A and 5 A CT inputs, which makes retrofits easier and keeps onsite wiring changes to a minimum. In many cases, you get the essentials without the complexity or footprint of heavier multifunction platforms.

Order Placement Process and Guarantees

• Warranty: 365 days
• Delivery: 1 week if in stock; no more than one month at the latest
• Payment: 50% advance payment; full payment before delivery
• Express options: FedEx, UPS, DHL

We typically pre‑check firmware options and I/O maps before shipment so commissioning on site goes smoother. You might notice that cuts commissioning time, especially when replacing older non‑communicating relays.

Key Features

• Non‑directional OC & EF protection (50/51, 50N/51N) – Core feeder protection with definite‑time and inverse‑time curves, tuned for radial networks.
• 3‑phase CT + residual input – Supports 1 A/5 A phase CTs and a residual/neutral CT for sensitive earth‑fault detection.
• Multi‑setting groups – Quickly switch protection settings for normal, maintenance, or backup scenarios.
• Event and disturbance records – Fault data capture helps verify coordination and speeds up root‑cause analysis.
• Self‑supervision – Continuous internal diagnostics; alarm output if something doesn’t look right.
• SCADA connectivity – Serial communications for basic integration; protocol selection depends on the variant ordered.
• Compact flush‑mount design – Typically fits in MV panels and RMUs without door rework, making retrofits simpler.
• Breaker control and indications – Front indications with programmable logic I/O for trips, alarms, and interlocks.

A utility customer recently told us they swapped aging electromechanical relays with REJ603 units in a compact substation and, despite the tight panel space, the swap went quicker than expected because of the CT flexibility and straightforward wiring layout.

Technical Specifications

Related or Supporting Products

• ABB REF615 – Feeder protection with directional EF and full IEC 61850; more advanced logic and arc‑flash options.
• ABB REJ601 – Similar concept to REJ603 for basic non‑directional feeder applications; fewer communication options in many cases.
• ABB REF620 – Higher I/O density and extended protection functions for complex feeders; suitable when you need more scheme logic.
• ABB REM615 – If your circuit is actually a motor feeder, REM615 is purpose‑built for motors with thermal models and start supervision.
• Core‑balance CT (CBCT) – For sensitive earth‑fault detection with the residual input; sizes chosen per feeder cable OD.

Installation & Maintenance

• Mounting & cabinet – Install in a clean, dry switchgear panel with proper bonding. From my experience, leaving 50–80 mm behind the relay helps with CT and trip‑coil wiring.
• Wiring – Observe CT polarity (S1/S2), short CTs before work, and segregate CT/VT leads from control wiring to reduce noise pickup.
• Ventilation – Provide basic airflow; avoid mounting directly above heat sources or in unventilated enclosures.
• Grounding – Use a single‑point protective earth for the relay case and cable screens to prevent ground loops.
• Commissioning – Secondary injection for 50/51 and 50N/51N pickup/time checks; verify trip circuits and binary I/O mapping.
• Routine maintenance – Annual function test and cleaning of terminals; export event/disturbance logs after any operation; update firmware when applicable and validated for your variant.
• Safety – De‑energize CT circuits correctly; use lockout/tagout; confirm settings groups and SCADA points before energization.

Quality & Certifications

• Standards – Type‑tested to relevant IEC protection and EMC standards (IEC 60255 series / IEC 61000 series).
• CE marking – Conforms to applicable EU directives for EMC and safety.
• RoHS – Components and build typically compliant with RoHS requirements.
• Manufacturer’s warranty – ABB’s standard warranty policy applies (commonly 12 months, region and terms may vary).
• Our coverage – 365‑day warranty and pre‑shipment functional verification to reduce onsite risk.

If you share your network earthing method and CT ratios, we can pre‑load a settings template so you’re not starting from a blank file during commissioning. That seems to save time in most cases.