Combined overcurrent and earth-fault relay SPAJ 321 C

Not active product since 2007

The combined overcurrent and earth-fault relay SPAJ 321 C is used for short-circuit protection, time overcurrent protection and residual earth-fault protection for radial overhead and cable feeders in solidly earthed or low-resistance earthed networks. The relay may also be used in a variety of other applications requiring phase overcurrent protection and/or residual earth-fault protection. The relay is especially used in applications based on the use of inverse time relays, both for overcurrent protection and earth-fault protection. 


  • Combined overcurrent and earth-fault protection

Product benefits

  •  Protection for a variety of applications 

Product features

  • Three-phase low-set overcurrent protection with inverse time or definite time characteristic
  • Three-phase, high-set, instantaneous or definite time overcurrent protection
  • Non-directional residual current earth-fault protection with inverse time or definite time characteristic
  • Non-directional, high-set, instantaneous or definite time, residual current earth-fault protection
  • Automatic doubling of the start current setting of the high-set stage of the earth-fault unit at start-up
  • Starting signals made available for the purpose of blocking cooperating protection relays
  • Control input for an incoming external blocking signal
  • Continuous self-supervision and auto-diagnostic fault indication to facilitate fault location and repair after detection of an internal relay fault

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