OVERCURRENT RELAYS REJ 525 ABB

Scope The REJ 52_ series comprises four protection relays; a single-phase residual overcurrent relay REJ 521, a three-phase phase overcurrent relay REJ 523, a combined three-phase phase and residual overcurrent relay REJ 525 and a directional residual overcurrent relay REJ 527. All four relays have two operating stages: a high-set stage and a low-set stage. The low-set stages of the relays can be given definite time or inverse time delay with all standard and several proprietary IDMT curves. Application The REJ 52_ overcurrent relay series is primarily intended for the overcurrent and earth-fault protection of utility substations and feeders, and industrial power distribution systems. The relays can also be used together with other protection relays in applications requiring short-circuit and earth-fault protection. The REJ 52_ relays have an external digital control input, which can be used to, e.g., block relay functions under certain conditions. This feature makes the relays ideal for busbar protection schemes based on blockings and for cascade relay schemes. REJ 521 is a single-phase, two-stage residual overcurrent relay for general non-directional earth-fault protection applications. REJ 523 is a three-phase, two-stage overcurrent relay for short-circuit and time overcurrent protection of substation feeders and busbars. REJ 525 is a combined phase and neutral overcurrent relay for short-circuit and time overcurrent protection and non-directional earth-fault protection of overhead lines and cable feeders
relay