5. Functions
5.1. Functions included in AQ-T257
This chapter presents the functions of AQ-T257 Transformer Protection IED. AQ-T257 includes
following functions and amounts of instances of the functions.
Table. 5.1. - 1. Protection functions of AQ-T257
Name
IEC
ANSI
Description
NOC1
NOC2
NOC3
NOC4
I>
I>>
I>>>
I>>>>
50/51
Overcurrent protection (4 stages)
NEF1
NEF2
NEF3
NEF4
I0>
I0>>
I0>>>
I0>>>>
50N/51N
Residual overcurrent protection (4 stages)
DOC1
DOC2
DOC3
DOC4
Idir>
Idir>>
Idir>>>
Idir>>>>
67
Directional overcurrent protection (4 stages)
DEF1
DEF2
DEF3
DEF4
I0dir>
I0dir>>
I0dir>>>
I0dir>>>>
67N
Directional residual overcurrent protection (4 stages)
CUB1
CUB2
CUB3
CUB4
I2>
I2>>
I2>>>
I2>>>>
46/46R/46L
Negative sequence overcurrent / phase current reversal / unbalance
protection (4 stages)
HOC1
HOC2
HOC3
HOC4
Ih>
Ih>>
Ih>>>
Ih>>>>
50h/51h/68h
Detection and blocking or tripping from selectable 2nd, 3rd, 4th, 5th, 7th,
9th, 11th, 13th, 15th, 17th, 19th harmonic. Phase currents and residual
currents separate stages. (4 stages)
CBF1
CBFP
50BF/52BF
Breaker failure protection
DIF1
Idb>
Idi>
87T
Transformer differential function. Biased and non-biased stages
REF1
REF2
I0d>
I0d>
87N
Low or high impedance restricted earth fault, cable end differential
protection
TOLT1
TT>
49L
Transformer thermal overload protection
TRF
TRF
-
Transformer status monitoring function
RTD1
RTD
49T
Resistance Temperature Detectors for temperature measurements
OV1
OV2
OV3
OV4
U>
U>>
U>>>
U>>>>
59
Overvoltage protection (4 stages)
UV1
UV2
UV3
UV4
U<
U<<
U<<<
U<<<<
27
Undervoltage protections (4 stages)
VUB1
VUB2
VUB3
VUB4
U1/U2>/<
U1/U2>>/<<
U1/U2>>>/<<<
U1/U2>>>>/<<<<
47/27PN/59PN Sequence voltage protection (4 stages)
NOV1
NOV2
NOV3
NOV4
U0>
U0>>
U0>>>
U0>>>>
59N
Neutral voltage protection (4 stages)
AQ-T257
Instruction manual
Version: 2.00
11
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