1MRS751802-MUM
REX 521
97
Protection Relay
Technical Reference Manual, Standard Configurations
7.1.7.
3I2f>
The function block 3I2f> can be used for doubling the set start current of overcurrent
protection in a transformer magnetizing inrush situation, or at motor start-up, or for
blocking (stabilizing) overcurrent protection in a transformer magnetizing inrush
situation.
Fig. 7.1.7.-1
Function block symbols of 3I2f>
Three-phase under voltage protection, high-set stage, 3U<<
Start voltage
0.10...1.20 x Un
Operate time
0.1...300.0 s
Operation mode
Not in use
Definite time
C curve
Measuring mode
Mode 1 (Phase-to-phase voltages / Peak-to-peak meas.)
Mode 2 (Phase-to-phase voltages / Fundam.freq.)
Mode 3 (Phase-to-earth voltages / Fundam.freq.)
Note! The values below apply when f/fn = 0.95...1.05
Operation accuracy
±2,5% of the set value with Measuring Mode 3
±1,0% of the set value with Measuring Modes 1 and 2
Start time
Injected voltages < 0.5 x start voltage:
internal time < 32 ms
total time < 40 ms
Reset time
40...1000 ms
(depends on the minimum pulse width set for the trip
output)
Reset ratio, typically
1.04
(depends on the value of the
Oper.
hysteresis
parameter, refer to the manual of the
Three-phase Undervoltage Protection function,
1MRS752333-MUM, chapters 2.3.1. and 3.2.4.)
Retardation time
< 60 ms
Operate time accuracy in DT mode
±2,5% of set value
Three-phase transformer inrush and motor start-up current detector inrush3, 3I2f>
Ratio I 2f/I 1f
Start current
Operation mode
5...50%
0.10...5.00 x ln
Not in use
Inrush mode
Start-up mode
Operation accuracy
Start time
Note! The values below apply when f/fn=0.95...1.05
Current meas.: ±2.5% of set value or ±0.01 x ln
Ratio I 2f/I 1f measurement: ±5.0% of set value
Internal time <32 ms
Total time <40 ms
GROUP
START
3I
2f
/I
1f
>
3dI/dt>
3I2f>
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