High impedance relay

High impedance relay – Reyrolle 7PG23

Reyrolle 7PG23

The 7PG23 electro-mechanical single phase circulating current protection is used to detect earth faults in ‘high impedance’ protection schemes. The relay is typically applied used in transformer protection schemes.

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Features & functions

High impedance relay Reyrolle 7PG23


One relay per phase can be applied to detect both phase and earth faults e.g. on reactors and stator windings of large machines.


The relay is a voltage operating device and has a user selectable operate voltage setting. The relay can be used in conjunction with an external shunt setting resistor where a higher operating current is required. An integral non-linear resistor limits over-voltages occurring during system faults. Operation flag indicator. Relays are housed in size E3 cases.


  • User selectable voltage setting

  • Integral voltage limiting device

  • Operation flag indicator


Protection functions

  • High impedance restricted earth fault