ABB REX 521, Technical Reference Manual, Standard Configurations

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90
1MRS751802-MUM Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
7.1.3. Io>->, Io>>-> and Io>>>->
The directional earth fault protection function blocks Io>->, Io>>-> and Io>>>-> are
designed to be used for directional or non-directional earth fault protection
whenever the DT characteristic or, as concerns Io>->, the IDMT (Inverse Definite
Minimum Time) characteristic is appropriate. Suppression of harmonics is possible.
Fig. 7.1.3.-1 Function block symbols of Io>->, Io>>-> and Io>>>->
Non-directional earth fault protection, high-set stage, Io>>, and instantaneous stage,
Io>>>
Start current
Operate time
Operation mode
Measuring mode
Drop-off time of the operate time counter
0.10…12.00 x In
0.05…300.00 s
Not in use
Definite time
Instantaneous
Peak-to-peak
Fundamental frequency
0...1000 ms
Note! The values below apply when f/fn = 0.95...1.05
Operation accuracy
Operate time
Reset time
Reset ratio, typically
Retardation time
Operate time accuracy in DT mode
±2.5% of set value or + 0.01 x In
Injected currents > 2.0 x start current:
internal time < 32 ms
total time < 40 ms
40...1000 ms (depends on the minimum pulse width set
for the trip output)
0.95
< 45 ms
±2% of set value or ±20 ms
CBFP
BACTRL
BS1
BS2
GROUP
RESET
START
TRIP
CBFP
Io>
BACTRL
BS1
BS2
GROUP
RESET START
TRIP
CBFP
Io>>
CBFP
BACTRL
BS1
BS2
GROUP
RESET
START
TRIP
CBFP
Io>>>
CBFP