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 226: 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".
Restoring mode Description
Disabled Load restoration is disabled.
Auto In the “Auto” mode, input frequency is continuously compared to the
Restore start Val
setting. The restore detection module includes a
timer with the DT characteristics. Upon detection of restoring, the
operation timer activates the ST_REST output. When the timer has
reached the value of the
Restore delay time
setting, the RESTORE
output is activated if the restoring condition still persists. If the fre-
quency drops below the
Restore start Val
before the RESTORE output
is activated, the reset timer is activated. If the reset timer reaches
the value of the
Reset delay time
setting, the timer resets and the
ST_REST start output is deactivated.
Manual In the “Manual” mode, a manual restoration is possible through the
MAN_RESTORE input or via communication. The ST_REST output is
activated if the MAN_RESTORE command is available and the frequen-
Protection functions 1MRS758755 C
460 REC615 & RER615
Technical Manual
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