50 Hz
Start value Freq set at 0.975 xFn
Start value df/dt set at -0.020 xFn/s
Operate Tm df/dt = 500ms
Operate Tm Freq = 1000ms
Load shed mode = Freq< AND df/dt
49 Hz
ST_FRG
OPR_FRG
500ms
1s
OPERATE is not
activated in this case
as Freq< condition not
satisfied
OPERATE
Start of operation timer
Time [s]
Frequency
[Hz]
Figure 371: Load-shedding operation in the “Freq< AND df/dt>” mode when only the
df/dt condition is satisfied ( Rated frequency=50 Hz)
Restore detection
If after the activation of the OPERATE input the frequency recovers to a level above
the
Restore start Val
setting, the RESTORE signal output is activated. The RESTORE
output remains active for a 100 ms. The
Restore mode
setting is used to select the
restoring mode to be "Disabled", "Auto" or "Manual".
1MRS757644 H
Protection functions
620 series
Technical Manual
713
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