ABB RELION 620 Series Technical Manual page 716

Section 4
Protection functions
710
Frequency
[Hz]
50 Hz
49 Hz
48.75 Hz
ST_FRG
Start of operation timer
OPR_FRG
ST_FRQ
OPR_FRQ
OPERATE
GUID-143A36EB-FCC9-4E87-B615-7743A3D75A15 V2 EN
Figure 360: 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
1MRS757644 F
Time [s]
1s
as Freq< AND df/dt
condition satisfied
Technical Manual
620 series