Multifunction protection

Multifunction protection – SIPROTEC 7SJ66


SIPROTEC 7SJ66 is a numerical protection, control and monitoring device.  SIPROTEC 7SJ66 is features flexible protection functions. Up to 20 protection functions can be added according to individual requirements. Thus, for example, a rate-of-frequency-change protection or reverse power protection can be implemented. The relay provides control of the circuit-breaker, further switching devices and automation functions. The integrated graphical logic editor (CFC) allows the user to implement its own functions, e. g. for the automation of switchgear (interlocking). The communication interfaces support the easy integration into modern communication networks.

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Features & functions

Multifunction protection SIPROTEC 7SJ66



  • Spring-type terminals
  • 4 current transformers
  • 4 voltage transformers
  • 16 to 36 binary inputs
  • 7 to 23 output relays
  • Graphic or 8 line display

Communication interfaces


  • System port:
    – IEC 61850
    – DNP TCP
    – IEC 60870-5-103
    – Modbus RTU
    – DNP3
  • Electrical and optical interface
  • RSTP (Redundancy Protocol for Ethernet)
  • Service interface for DIGSI 4 or RTD-Box
  • Front USB interface for DIGSI 4
  • Time synchronization via IRIG B, DCF77



Protection functions

  • Overcurrent protection

  • Directional overcurrent protection

  • Sensitive directional ground-fault detection

  • Displacement voltage

  • Intermittent ground-fault protection

  • Directional intermittent ground fault protect

  • High-impedance restricted ground fault

  • Inrush restraint

  • Motor protection

  • Overload protection

  • Temperature monitoring

  • Under-/overvoltage protection

  • Under-/overfrequency protection

  • Rate-of-frequency-change protection

  • Power protection (e.g. reverse, factor)

  • Undervoltage controlled reactive power protection

  • Breaker failure protection

  • Negative-sequence protection

  • Phase-sequence monitoring

  • Synchro-check

  • Fault locator

  • Lockout

  • Auto-reclosure
  • Admittance ground-fault protection


Control functions/programmable logic

  • Commands for control of CB and of isolators

  • Graphical visualization of switch positions

  • Control via keyboard, binary inputs, DIGSI 4 or SCADA system

  • User-defined logic with CFC (e.g. interlocking)

Monitoring functions

  • Operational measured values V, I, f

  • Energy metering values Wp,Wq

  • Circuit-breaker wear monitoring

  • Slave pointer

  • Trip circuit supervision

  • Fuse failure monitor

  • 8 oscillographic fault records with a sampling rate of 1.6 kHz

  • Motor statistics
  • Security log



  • English, Spanish, Russian, Polish and Turkish


  • Line and feeder protection: 
    Protection of high and medium voltage networks with earthed (grounded), low-resistance grounded, isolated or compensated neutral point

  • Motor Protection: 
    Suitable for asynchronous machines of all sizes

  • Backup Protection: 
    The relay performs all functions of backup protection supplementary to transformer differential protection