Directional overcurrent protection

Directional Overcurrent Protection – Reyrolle 7SR120

Reyrolle 7SR120

The 7SR12 includes directional control of the overcurrent and earth fault functionality and is typically installed where fault current can flow in either direction i.e. on interconnected systems. These relays are typically applied to provide the main protection on feeders and interconnectors and the back-up protection on items of plant such as transformers. On distribution system circuits overcurrent and earth fault protection are often the only protection installed.

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Features & functions

Directional overcurrent protection Reyrolle 7SR120


The relay functionality allows highly flexible settings for current and time grading making it compatible with all types of overcurrent protection.


The relays are available in single and four pole variants housed in E4 cases with the IEC61850 protocol option housed in an E6 case. Integrated logic is provided to allow the optimal configuration of relay functionality with the relays analogue inputs and binary input/output circuits.


Protection, instrumentation and metering functionality is accessible via data comms channel(s). A front USB port for local PC connection or rear electrical RS485 port for remote connection is provided.


  • Cold load settings

  • Four settings groups

  • Password protection - 2 levels

  • User programmable logic

  • Self-monitoring

  • Circuit breaker trip counter and timer

  • Fault, event and waveform records


Protection functions

  • Undercurrent (37)

  • Broken conductor (46BC)

  • Negative phase sequence overcurrent (46NPS)

  • Thermal overload (49)

  • Overcurrent (50, 51)

  • Earth fault (50G, 50N, 50SEF, 51G, 51N, 51SEF)

  • Directional control of overcurrent & earth fault (67)

  • High impedance REF (64H)

  • Under/over voltage (27/59)

  • Negative phase sequence voltage (47)

  • Voltage controlled overcurrent (51V)

  • Neutral voltage displacement (59N)

Supervision functions

  • CT supervision (60CTS)

  • Trip & close circuit supervision (74T/CCS)

  • VT supervision (60VTS)

  • Inrush detector (81HBL2)

  • Circuit breaker fail (50BF)

Control functions

  • Auto reclose (79)

Monitoring functions

  • Primary/secondary current phases and earth direction

  • Primary/secondary line and phase voltages

  • Apparent power and power factor

  • Real and reactive power

  • W Hr & VAr Hr forward and reverse

  • Historical demand record

  • Positive phase sequence (PPS) voltage & current

  • Negative phase sequence (NPS) voltage & current

  • Zero phase sequence (ZPS) voltage