REJ603 relay is intended to be used for the selective short-circuit and earth-fault protection of feeders in secondary distribution networks and for protection of transformers in utilities and industries. The relay is a selfpowered Numerical relay, which does not require external auxiliary supply voltage, making it an ideal choice for installation even in remote locations where auxiliary supplies are not available. The relay derives power for its operation from the current transformers. REJ603 is primarily used in Ring Main Units ( RMU ) within distribution network.

Relay provides earth current measurement through internal calculation or has the provision for measuring it from the external core balance current transformer (CBCT).

The key features of the relay are:

•  Self-powered three phase non-directional overcurrent and earth-fault
• protection with DMT and IDMT characteristics
•  Dual mode of earth fault measurement – internal vector summation
• or external CBCT input
•  Integrated IDMT curves (IEC and Special) in a single product to
• cover time co-ordination needs of secondary distribution protection
•  Protection blocking by second harmonic measurement for stability
• during magnetizing inrush of transformers
•  Capacitor discharge impulse output for low energy trip coil
•  Built-in hand-reset electromagnetic flag for trip indication
•  Easy setting by DIP switches, protected by a transparent cover
•  Compact design and mounting arrangement suitable for Ring Main
• Unit (RMU) / secondary switchgear applications
•  Test facility for testing entire scheme including primary CT, relay
• and trip coil
•  Signal output for trip indication to external system