ABB Relion REC615 - Page 459

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 activated
as Freq< AND df/dt
condition satisfied
OPERATE
48.75 Hz
Start of operation timer
ST_FRQ
OPR_FRQ
Start of operation timer
1s
Time [s]
Frequency
[Hz]
Figure 225: Load-shedding operation in the “Freq< AND df/dt>” mode when both
Freq< and df/dt conditions are satisfied ( Rated frequency=50 Hz)
1MRS758755 C
Protection functions
REC615 & RER615
Technical Manual
459