Directional or non-directional earth-fault relay REJ 527

Basic protection of busbars and feeders in utility substations and industrial power distribution systems

Not active product since 2009

The directional or non-directional earth-fault relay REJ 527 is a secondary relay which is connected to the voltage and current transformers of the object to be protected. The earth-fault current and the zero-sequence voltage unit continuously measure the zero-sequence voltage, earth-fault current and phase angle of the object. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions.

The voltage unit includes low-set stage U0b> and the earth-fault current unit low-set stage I0 > and high-set stage I0 >>. The earth-fault stages can be replaced by two additional voltage stages, low-set stage U0 > and high-set stage U0 >>.

The protection functions are independent of each other and have their own setting groups and data recordings. The voltage and current functions use conventional transformer measurement.

An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.


  • Directional earth-fault protection relay is used as a secondary relay which is connected to the current transformers of the object to be protected

Product benfits

  • Flexible tripping and signalling facilities

Product features

  • Directional or non-directional low-set earth-fault current stage I0> with definite-time or inverse definite minimum time (IDMT) characteristic
  • Directional or non-directional high-set earth-fault current stage I0>> with definite-time characteristic
  • Deblocking zero-sequence voltage stage U0b>
  • The two earth-fault current stages configurable to operate alternatively as two voltage stages: a three-stage voltage monitoring operation possible
  • Intermittent earth-fault protection
  • Circuit-breaker failure protection (CBFP)
  • Disturbance recorder
  • HMI with an alphanumeric LCD and manoeuvring buttons
  • Continuous self-supervision

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