Our differential protection relay, Reyrolle7SR18, is a numeric three phase differential protection relay used to detect in zone phase and earth faults. This differential protection relay is applied to overhead line and underground cable circuits as well as shorter circuits such as interconnectors.Reyrolle 7SR18 differential protection relays have integral back-up overcurrent/earth fault protection and intertripping channels.Protection 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 protection functionality with the relay's 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.