AQ-T257 Transformer Protection IED
AQ-T257 is a transformer protection IED with differential protection function and integrated AVR function. The AQ-T257 transformer protection IED provides also for complete current and voltage based protection functions and full measurements. Up to 9 optional I/O or communication cards are available for extensive monitoring and control applications. The AQ-T257 communicates using various protocols including IEC 61850 substation communication standard.
Highlight
- Large I/O capability 2nd and 5th harmonic blocking
- Automatic / manual voltage regulating (AVR)
- Complete transformer protection
- 2nd and 5th harmonic blocking
- Automatic verification of connection group and nominal value settings
- Through fault and overloading statistics for preventive maintenance
- Up to class 0.2S power and energy measuring

Protection |
---|
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) |
Directional overcurrent, 4 stages INST, DT or IDMT (67) |
Directional (sensitive) earth-fault, 4 stages INST, DT or IDMT (67N) |
Overvoltage, 2 stages INST, DT or IDMT (59) |
Undervoltage, 2 stages INST, DT or IDMT (27) |
Zero sequence overvoltage, 2 stages INST, DT or IDMT (59N) |
Positive/Negative sequence overvoltage, 2 stages INST, DT or IDMT (59N/47) |
Over/under frequency, 4 stages INST or DT (81O/81U) |
Rate of change of frequency, 4 stages INST or DT or IDMT (81R) |
Volts per hertz (24) |
Breaker failure protection (50BF/52BF) |
Arc protection (option) (50ARC/50NARC) |