ABB RELION REX640 Technical Manual page 857

1MRS759142 C
REX640
Technical Manual
Frequency
[Hz]
50 Hz
49 Hz
ST_FRG
Start of operation timer
OPR_FRG
OPERATE
GUID-BE9CEC60-6407-4F66-B82C-4B0E6FB876AD V1 EN
Figure 459: 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 output the frequency recovers to a level above
the Restore start Val setting, the RESTORE signal output is activated. The RESTORE
output remains active for 100 ms. The Restore mode setting is used to select the
restoring mode to be "Disabled", "Auto" or "Manual".
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
1s
500ms
OPERATE is not
activated in this case
as Freq< condition not
satisfied
Section 4
Protection functions
Time [s]
851