High impedance protection

High impedance protection – Reyrolle 7SR23

Reyrolle 7SR23

The 7SR23 DAD is a numeric high impedance circulating current relay that has four current inputs, it is used as a unit protection to detect phase and earth faults.

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Features & functions

High impedance protection Reyrolle 7SR23


The relay can be applied to busbars, connections, transformers, reactors and motors.


The relay is used in ‘high impedance’ applications in conjunction with external stabilising resistors and non-linear resistors (Metrosils). Standardised external components can be provided in an Epsilon case to facilitate design and installation.


The integral CT supervision feature detects open circuits in the CT secondary wiring circuits, a consideration where CT circuits are switched.


Relays are housed in E6 or E8 cases. Integrated logic is provided to allow the optimal configuration of relay input and output functionality. Protection, instrumentation and metering functionality is accessible via data comms channels. A front fascia USB port for local connection and RS485 rear port for remote connection are provided as standard, additional rear ports are available as options.


Protection functions

  • Overall differential protection 87/50(G)

  • Restricted earth fault protection 87REF

  • Earth fault (50G)

Supervision functions

  • CT supervision (CT50)

  • Fault clearance monitor (87/50BF)

Monitoring functions

  • Instrumentation

Further functions

  • IEC 61850 option

  • Eight settings groups

  • Password protection

  • Self monitoring

  • Fault, event and waveform records