ABB REF 541 Product Manual page 65

Feeder Terminal
= multiple-stage three-phase overcurrent protection, low-set, high-set and instantaneous
3I > 50/51
stage available
3I> 67 = multiple-stage three-phase directional overcurrent protection, low-set, high-set and
instantaneous stage available
I > 67N = multiple-stage directional earth-fault protection, low-set, high-set and instantaneous
0
stage available
I > = instantaneous stage for earth-fault protection, to operate in the event of a double earth
51N
0-0
fault in isolated or impedance earthed networks
I > = multiple-stage earth-fault protection, low-set, high-set and instantaneous stage
50N/51N
0
available
51N = low-set stage for sensitive earth-fault protection, to operate in the event of a high
SEF
resistive earth fault in effectively or low-impedance earthed networks
50/51
3I > = multiple-stage three-phase overcurrent protection, one stage dedicated for blockable
busbar overcurrent protection
51B
= three-phase overvoltage protection, low-set and high-set stage available
3U > 59
3U < 27 = three-phase undervoltage protection, low-set and high-set stage available
= multiple-stage residual overvoltage protection, low-set, high-set and instantaneous
U > 59N
0
stage available
= inrush detection based on the 2nd harmonic content of phase currents, applied for
3I > 68
2f
preventing possible unnecessary operation of overcurrent or earth-fault protection
during transformer switching-in or to start cold load pick-up logic
DI>
= phase discontinuity protection
46
f < 81U
= underfrequency protection/load shedding scheme
3
49F = thermal overload protection for feeders
= multiple-shot auto-recloser
0 I 79
SYNC 25
= circuit breaker synchro-check/direction of energizing check function
D 87T = differential protection for transformers
3 I >
D = restricted earth-fault protection, low- or high-impedance type
87N
I >
0
I > 68 = inrush detection based on the 2nd harmonic content of neutral current, applied to
02f
prevent possible unnecessary operation of the earth-fault protection during transformer
switching-in
= circuit-breaker failure protection
CBFP * /62
Fig. 18 Symbol notations, part I
REF 541, REF 543, REF 545.
1MRS750443-MBG
SYMNOT1
65