ABB REJ603 Self-Powered Protection Relay

The ABB REJ603, also cataloged as the REJ603 Self-Powered Protection Relay, operates as a dedicated hardware component for current-transformer-powered overcurrent and earth-fault protection within secondary distribution switchgear platforms. The hardware assembly derives its operational power directly from the primary measurement current transformers, removing dependencies on auxiliary voltage supplies. It evaluates physical current vectors in real time to calculate trip parameters and command breaker actuation coils during fault transients in ring main units.

Hardware Specifications

I/O Density Scaling and Deterministic Substation Performance

The REJ603 architecture coordinates with secondary distribution systems where localized I/O density scaling must be completed within tight physical cabinet envelopes. Data telemetry and binary event logging align with standard backplane bus communication velocity protocols inside shared switchgear cells. While operating independently of external control loops to maintain autonomous fault clearing, the module's processing logic retains firmware flash compatibility to support standardized calibration settings via matching Relion configuration tools across adjacent feeder networks.

Frequently Asked Questions

Q: How does the REJ603 execute a circuit breaker trip command if no auxiliary battery supply is present?

A: The relay stores energy harvested from the current transformer measurement circuits within an internal capacitor bank. Upon reaching a programmed overcurrent or earth-fault threshold, this stored energy discharges as a low-energy electrical pulse to actuate a specialized low-energy trip coil on the breaker.

Q: What happens to the protection logic during periods of extremely low load current on the feeder?

A: The relay requires a minimum primary phase current (typically 0.1 x In) to power up its internal microprocessor. Below this threshold, the system remains unpowered, but if a sudden fault occurs, the rapid rise in current energizes the processor and executes the programmed trip curve within millisecond tolerances.