Capacitor bank protection

Capacitor bank protection – Reyrolle 7SR191

Reyrolle 7SR191

The 7SR191 Capa is a numerical protection relay with a highly comprehensive functional software package.

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Features & functions

Capacitor bank protection Reyrolle 7SR191


The market for power capacitors is continually growing due to the expanding power network driven by increased customer demand.  Power capacitors improve the performance, quality and efficiency of the system and minimize power loss.  The Reyrolle 7SR191 Capa protection relay is designed with all of the necessary functionality for use on shunt connected distribution capacitor banks arranged in all of the common connection configurations:

  • Single star

  • Double star

  • Delta

  • H configuration

The Reyrolle 7SR191 Capa is a numerical protection device with a highly comprehensive functional software package which includes a range of integral application functions aimed at reducing installation, commissioning, wiring and engineering time.


  • User selectable hardware configuration to suit different bank arrangements
    - 3 pole overcurrent  + 1 pole unbalance
    - 1 pole overcurrent + 3 pole unbalance

  • Optional voltage inputs

  • Re-energisation blocking to prevent CB closing until the bank has self discharged

  • Overvoltage protection by integration analysis of current

  • Suitable for use with both internally/externally fused and fuseless capacitors

  • User programmable characteristics for all inverse voltage, current and thermal curves

  • Unbalance protection with natural spill compensation


Protection functions

  • Fascia programmable

  • CB control via fascia, binary inputs and communication SCADA system

  • User definable logic both via Quicklogic equations and a graphical design tool

  • Multiple setting groups

  • Measured values

  • Fault records

  • Disturbance waveform records

  • Event records

  • 6 User alarms for LCD text indications

  • Trip circuit supervision

  • Close circuit supervision

  • Virtual input/output

  • CB operation counts

  • Demand metering

  • Harmonic analysis and THD

  • Undercurrent/Loss of Supply (37)

  • Phase unbalance (46M)

  • Negative phase sequence overcurrent (46NPS)

  • Thermal overload (49)

  • Instantaneous overcurrent (50)

  • Instantaneous earth fault (50N)

  • Circuit breaker fail (50BF)

  • Time delayed overcurrent (51)

  • Time delayed derived earth fault (51N)

  • Overvoltage by current integration (59C)

  • Capacitor unbalance current (60C)

  • High impedance REF (87REF)

  • Under/overvoltage (27/59)

  • Negative phase sequence voltage (47)

  • Neutral voltage displacement (59N)

  • Directional instantaneous overcurrent  (67/50)

  • Directional instantaneous rarth fault (67/50N)

  • Directional time delayed overcurrent (67/51)

  • Directional time delayed earth fault (67/51N)

  • Under/over frequency (81)