Motor protection

Motor protection - 7SR57

Reyrolle 7SR57

The 7SR57 motor protection devices include a wide range of protection functions and IEC 61850 Ethernet communications as standard.

Motor protection Reyrolle 7SR57

Features & functions

The large LCD, tactile pushbuttons and programmable LEDs provide a user-friendly product interface and the relay element is withdrawable for easy replacement. To further minimize the product variants the power supply and the binary inputs cover the full operating range with configurable binary input thresholds.


The Reyrolle 5 is designed for the electricity networks of the future with enhanced communications and cybersecurity while maintaining a user-friendly interface and easy product management.


The 7SR57 motor protection devices include a wide range of protection functions and IEC 61850 Ethernet communications as standard. To further minimize the product variants the power supply and the binary inputs cover the full operating range with configurable binary input thresholds.


The large LCD, tactile pushbuttons and programmable LEDs provide a user-friendly product interface and the relay element is withdrawable for easy replacement.


Inputs and outputs
Current inputs – 4 or 8

Voltage inputs – 0 or 4

Binary inputs (max) – 29

Binary outputs (max) incl. healthy contact – 16

Arc flash detector inputs (AFD) – 0 or 3

High speed binary outputs (HSBO) – 0 or 3

Temperature sensor inputs (TSI) – 0, 8, or 16


Standard front USB port (for configuration using Reydisp Manager 2, a PC based software tool) rear

RS485, 2 x RJ45 electrical ports or optional optical Ethernet connections.


Size 6, 8, or 12 with withdrawable design.



Backlit 128 x 128 LCD with text and graphical display capabilities suitable for single line mimic diagrams.


Standard functionality

  • 14 Locked rotor protection
  • 37/37G Undercurrent protection – phase/earth
  • 46BC Broken conductor detection
  • 46PR Phase-rotation reversal
  • 46UB Phase unbalance
  • 48 Starting-time supervision
  • 49M Motor thermal overload protection
  • 49TS Temperature sensor supervision 1
  • 50/ 50N/ 50G  Instantaneous overcurrent/earth fault
  • 50AFD Arc flash detection2
  • 50BCL Break capacity limit
  • 50BF Circuit-breaker failure protection – 3 pole
  • 51/51G/51N Time delayed overcurrent/earth fault
  • 52 Circuit-breaker control
  • 60CTS CT supervision
  • 74CC/74TC Close‑circuit and trip‑circuit supervision
  • 81B Backspin monitor
  • 81HB2 Inrush current detection
  • 86 Lockout
  • 87GH Restricted earth fault protection – high‑impedance
                                                                1 An external interface unit is required where optional TSI module not fitted
                                                                2 Requires external components

Additional Functionality – Devices with VT Inputs

  • 27/27Vx Undervoltage protection
  • 32 Power protection
  • 47 Sequence overvoltage protection
  • 55 Power factor
  • 59/ 59Vx Overvoltage protection
  • 59N Neutral voltage displacement
  • 60VTS VT supervision
  • 67/67G/67N Directional – phase/earth fault
  • 81 Frequency protection – "f>" or "f<"
  • 81B-V Backspin monitor – voltage reference
  • 87M Motor differential protection

Monitoring functions

  • Primary, secondary and phase sequence current and voltage
  • Frequency, power and energy
  • Fault data, event and waveform records
  • Motor start data log


  • IEC 60870‑5‑103, Modbus TCP, DNP3 TCP
    Modbus RTU, DNP3, IEC 61850, Modbus Client for connection to external RTD box


  • Motor protection functions designed to protect during all motor starting and running sequences
  • Thermal algorithm optimized to closely match the thermal characteristics of motors
  • Thermal monitoring via plant temperature sensors supported


  • Compact design and low product life-cycle cost
  • Reliable operation due to powerful, proven protection algorithms
  • IEC 61850 Edition 1 & 2 with HSR, PRP and RSTP operation for increased availability
  • Simple product ordering
  • Combined 1 A and 5 A current transformer inputs
  • 28 programmable tri-color LEDs for clear indications.
  • User selectable languages: English, French, German, Portuguese, Spanish, Turkish
  • Conformal coating ordering option



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