Overview

The ABB REJ603 is a CT-powered feeder protection relay designed for medium-voltage secondary distribution networks. As part of the Relion® 605 series, it provides numerical overcurrent and earth-fault protection without requiring any auxiliary power — greatly enhancing reliability in locations where power availability is limited.

This makes the REJ603 highly suitable for unmanned substations, rural grids, and Ring Main Units (RMUs). It features both mechanical trip indication and electrical signaling, ensuring quick and visible fault confirmation even during outages.

Its compact, plug-and-play construction simplifies installation, while its robust environmental tolerance ensures long-term service in harsh industrial and utility environments.

Technical Data

Typical Applications

The REJ603 is widely used in secondary distribution systems, including:

• Compact substations

• Ring Main Units (RMUs)

• Rural overhead line feeders

• Industrial MV switchgear

• Unmanned and remote substations

Because it is self-powered, it reduces wiring complexity, lowers installation costs, and continues to function reliably during auxiliary supply failures — ensuring improved network resilience and quicker fault isolation.

Therefore, the REJ603 plays a vital role in maintaining distribution grid reliability and service continuity, especially in decentralized systems.

FAQ

Q1: Does the REJ603 require auxiliary power?
A1: No. It is fully powered by current transformers (CT self-powered).

Q2: What protection functions does it include?
A2: Overcurrent protection and earth-fault protection.

Q3: What environments is it designed for?
A3: Secondary distribution networks such as RMUs, rural substations, and compact switchgear.

Q4: Can it provide remote fault signaling?
A4: Yes. Optional outputs support remote trip and fault indication.

Q5: Is it suitable for harsh conditions?
A5: Yes. It operates from –25°C to +55°C and complies with IEC protection standards.