ABB REX 521, Technical Reference Manual, Standard Configurations

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1MRS751802-MUM Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
7.1.5. 3U> and 3U>>
Abnormal busbar voltages can be caused by faults in the network or a faulty tap
changer or voltage regulator of a power transformer. The function blocks are
designed for the single-phase, two-phase and three-phase overvoltage protection
whenever the DT characteristic or, as concerns 3U>, the IDMT (Inverse Definite
Minimum Time) characteristic is appropriate. Suppression of harmonics is possible.
Fig. 7.1.5.-1 Function block symbols of 3U> and 3U>>
Three-phase directional overcurrent protection, high-set stage, 3I>>->
Start current 0.05…40.00 x In
Operate time 0.05…300.00 s
Operation mode Not in use
Definite time
Instantaneous
Basic angle
ϕ
b
0...90
Oper. Direction Forward
Reverse
Earth fault pr. Disabled
Enabled
Nondir. operat. Disabled
Enabled
Measuring mode Mode1 (Phase-to-phase voltages/Peak-to-peak currents)
Mode2 (Phase-to-phase voltages/Fund. freq. Currents)
Mode3 (Phase-to-earth voltages/Peak-to-peak currents)
Mode4 (Phase-to-earth voltages/Fund. freq. Currents)
Drop-off time of the operate time counter 0...1000 ms
Note! The values below apply when f/fn = 0.95...1.05
Operation accuracy Current:
0.1...10 x In: ±2.5% of set value or ±0.01 x In
10...40 x In: ±5.0% of set value
Start time
Voltage:
±2.5% of measured value or ±0.01 x Un
Phase angle: ±2°
Injected currents > 2.0 x start current:
internal time < 42 ms
total time < 50 ms
Reset time 40...1000 ms (depends on the minimum pulse width set
for the trip output)
Reset ratio, typically 0.95
Retardation time < 45 ms
Operate time accuracy in DT mode ±2% of set value or ±20 ms
BS1
BS2
GROUP
RESET
START
TRIP
3U>
BS1
BS2
GROUP
RESET
START
TRIP
3U>>