7SR18

  • 3-phase, phase segregated current differential protection
  • Overcurrent
  • Earth Fault
  • Protection comms link supervision
  • Circuit Breaker Fail
  • CT Supervision
  • Trip Circuit Supervision
  • Intertripping
  • CT ratio correction
  • IEC61850 Goose Capable




The 7SR18 is a numeric three phase differential protection used to detect in zone phase and earth faults. The relay is applied to overhead line and underground cable circuits as well as shorter circuits such as interconnectors.

The relays have integral back-up overcurrent/earth fault protection and intertripping channels.

Relays (and associated CTs) are installed at each end of the protected circuit. The relays are connected together with a fully supervised fibre optic protection communications link.