ABB RELION REX640 Technical Manual page 856

Section 4
Protection functions
850
Frequency
[Hz]
50 Hz
49 Hz
48.75 Hz
ST_FRG
Start of operation timer
OPR_FRG
ST_FRQ
OPR_FRQ
OPERATE
GUID-39374303-04DD-4BFD-8554-F35C60F5B3FF V1 EN
Figure 458: Load-shedding operation in the "Freq< AND df/dt>" mode when both
Freq< and df/dt conditions are satisfied (Rated frequency=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
1s
500ms
Start of operation timer
OPERATE is activated
1MRS759142 C
Time [s]
1s
as Freq< AND df/dt
condition satisfied
Technical Manual
REX640