Transformer protection

Transformer Protection – Reyrolle 7SR242

Reyrolle 7SR242

The 7SR242 is used as a protection, control and monitoring relay for two winding transformers of all vector groups, primary configurations/connections and earthing connections.

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Features & functions

Transformer protection Reyrolle 7SR242


The relay functionality also allows its application in auto-transformer and reactor protection schemes.


Relays are housed in size E8 or E10 cases. Integrated logic is provided to allow the optimal configuration of relay functionality with the relays analogue inputs and binary input/output circuits.


Protection, control, 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. Additional rear port options are available.


  • Cold load settings

  • Eight settings groups

  • Password protection - 2 levels

  • User programmable logic

  • Self-monitoring

  • Circuit breaker trip counters

  • Fault, event and waveform records


Protection functions

  • Over-fluxing (24)

  • Under/over-voltage (27/59)

  • Undercurrent (37)

  • Negative phase sequence overcurrent (46NPS)

  • Thermal overload (49)

  • Overcurrent (50, 51)

  • Earth fault (50G, 50N, 51G, 51N)

  • Neutral voltage displacement (59N)

  • High impedance REF (64H)

  • Biased differential (87BD)

  • High-set differential (87HS)

Supervision functions

  • Circuit breaker Fail (50BF)

  • Trip circuit supervision (74TC)

  • Inrush detector (81HBL2)

  • Over-fluxing detector (81HBL5)

Monitoring functions

  • Primary/secondary currents phases and earth direction

  • Relay operate and restraint currents

  • Positive phase sequence (PPS) current

  • Negative phase sequence (NPS) current

  • Zero phase sequence (ZPS) current

  • Thermal status

  • Primary/secondary single phase voltage

  • Frequency and fluxing

  • Historical demand record