ABB RELION 620 Series Technical Manual page 336

Section 4
Protection functions
330
value set by Trip Tm df/dt, the OPR_FRG output is activated if the df/dt condition still
persists. If df/dt becomes normal before the module trips, the reset timer is activated. If the
reset timer reaches the value of the Reset delay time setting, the timer resets and the
ST_FRG output is deactivated.
Load-shedding control
The way of load-shedding, that is, whether to operate based on underfrequency or high df/
dt or both, is defined with the Load shed mode user setting. The valid operation modes for
the Load shed mode settings are "Freq<", "Freq< AND df/dt" and "Freq< OR df/dt".
Once the selected operation mode conditions are satisfied, the PICKUP and TRIP output
signals are activated.
When the PICKUP output is active, the percentage of the elapsed delay time can be
monitored through PICKUP_DUR which is available as monitored data.
1MAC504801-IB E
620 series ANSI
Technical Manual