AQ-T256 Transformer Protection IED

AQ-T256 is a transformer protection IED with sophisticated and easy to use differential protection function. The AQ-T256 transformer protection IED provides for both low and high side overcurrent, earth-fault, negative sequence and two independent restricted earth-fault instances. Up to 10 optional I/O or communication cards are available for extensive monitoring and control applications. The AQ-T256 communicates using various protocols including IEC 61850 substation communication standard.


  • Large I/O capability
  • Predefined or custom connection group selection 2nd and 5th harmonic blocking
  • Automatic verification of connection group and nominal value settings
  • Through fault and overloading statistics for preventive maintenance
Protection Functions
2 winding transformer differential (87T)
High/low impedance restricted earth fault / cable end differential * (87N1, 87N2)
Transformer thermal overload (49T/49RTD)
Three-phase overcurrent, 2+2 stages INST, DT or IDMT (50/51)
Earth-fault (sensitive), 3 stages INST, DT or IDMT (50/51N)
Harmonic overcurrent / inrush blocking, 4 stages INST, DT or IDMT (50/51H, 68)
Current unbalance / broken conductor, 2+2 stages INST, DT or IDMT (46/46R/46L)
Breaker failure protection (50BF/52BF)
Arc protection (option) (50ARC/50NARC)