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2P49 Phase Failure Relay

The main earth fault protection relays in distributions systems, power stations & large manufacturing / processing plants can fail to detect a high impedance breakdown to earth causing hazard to human life & potential damage to plant & equipment. In these & other situations demanding extra sensitive earth fault protection, the 2P49 relay using solid state techniques, can be applied to detect earth currents down to 0.5% of the CT nominal current.

The 2P49 relay is a phase failure relay suitable for 3 phase supplies. The relay is designed to provide protection for rotating equipment from the damaging effects of excessive negative sequence voltage resulting from phase failure, phase unbalance and reversed phase sequence. The 2P49 output relay is normally energised and drops out when phase angle unbalance is greater than the pre-set, under voltage or reverse phase sequence. The 2P49 may also be applied in automatic voltage changeover schemes in preference to the 2P48 model where a neutral connection is not available or to reduce cost.


  • High sensitivity
  • Detects phase angle imbalance
  • Detects negative phase sequence
  • Detects supply undervoltage
  • Unaffected by frequency variations of + 5Hz
  • Adjustable 5-15% out of balance setting
  • Range of detection voltages & frequencies available
  • No auxiliary voltage required
  • Fail safe operation (Contact normally picked up)
  • Filter rejects harmonics & control tones
  • Size 2M28-S draw out case
  • Standard heavy duty contacts
  • Optional mechanical flag indication
  • Optional 2s approx. time delay on drop off function
  • Made in Australia

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©1998-2012 Relay Monitoring Systems Pty. Ltd.      ACN 052 484 483     ABN 76 052 484 483

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