ABB RELION 620 Series Technical Manual page 337

1MAC504801-IB E
620 series ANSI
Technical Manual
Frequency
[Hz]
60 Hz
58.8 Hz
58.5 Hz
ST_FRG
Start of operation timer
OPR_FRG
ST_FRQ
OPR_FRQ
TRIP
GUID-95AE7DA4-8BCE-4B1B-811F-7154C6A751A0 V3 EN
Figure 148: Load-shedding operation in the "Freq< AND df/dt>" mode when both
Freq< and df/dt conditions are satisfied (Rated frequency=60 Hz)
Pickup value Freq set at 0.975 xFn
Pickup value df/dt set at -0.020 xFn/s
Trip Tm df/dt = 500ms
Trip Tm Freq = 1000ms
Load shed mode = Freq< AND df/dt
1s
500ms
Start of operation timer
TRIP is activated as
Section 4
Protection functions
Time [s]
1s
Freq< AND df/dt
condition satisfied
331