Three Phase Unit Differential Protection Relay
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.
Relays have four current inputs and are housed in E6 cases.
Integrated logic is provided to allow the optimal configuration of relay functionality with the relays analogue inputs and binary input/output circuits.
Protection and instrumentation functionality is accessible via the data comms channel - a front USB, RS485 and IEC 61850 (optional) rear ports.
3-phase, phase segregated current differential protection
Protection comms link supervision
Circuit Breaker Fail
Trip Circuit Supervision
Primary/Secondary Current Phases and Earth
Historical Demand Record
CT ratio correction
Four Setting Groups
Circuit Breaker Trip Counter
Fault, event and waveform records
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