High impedance protection SPAE 010

Not active product since 2012

The SPAE relays are differential current earth-fault protection relays. Another name for differential current earth-fault is restricted earth-fault. In the SPAE-relays, the stability of the protection is based on the circumstance that the impedance of a current transformer quickly decreases as the current transformer saturates. The reactance of the excitation circuit of a fully saturated current transformer approaches zero and the impedance is purely winding resistance. By means of the resistor in the differential current circuit the secondary current fed by a non-saturated current transformer is forced to flow through the secondary circuit of a saturated current transformer.

The protection relays type SPAE 010 and SPAE 011 have identical functions. The only difference between the relays is their auxiliary supply voltage ranges. The auxiliary supply voltage range of the relay SPAE 010 is 80-265 V ac and that of SPAE 011 is 18-80 V dc.


  • High impedance type differential current earth-fault protection (restricted earth-fault)

Product benefits

  • Transformer asset protection

Product features

  • High impedance type differential current earth-fault protection, so called restricted earth-fault relay (REF)
  • Earth-fault protection relay for transformers, motors and generators
  • Required stabilizing resistors built-in into the relay
  • Short total operating time together and high stability
  • High immunity against all types of mechanical and electrical interference
  • High accuracy and long time stability features due to a digital and software based design

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