ABB RER620 Technical Manual page 234

Section 4
Protection functions
228
Figure 104: Load-shedding operation in the "Freq< AND df/dt>" mode when only the
df/dt condition is satisfied (Rated frequency=50 Hz)
Restore detection
If after the activation of the OPERATE input the frequency recovers to a level above the
Restore start Val setting, the RESTORE signal output is activated. The RESTORE output
remains active for a 100 ms. The Restore mode setting is used to select the restoring mode
to be "Disabled", "Auto" or "Manual".
Restoring mode Description
Disabled Load restoration is disabled.
Auto In the "Auto" mode, input frequency is continuously compared to the
setting. The restore detection module includes a timer with the DT characteristics.
Upon detection of restoring, the operation timer activates the ST_REST output. When
the timer has reached the value of the
is activated if the restoring condition still persists. If the frequency drops below the
Restore start Val
If the reset timer reaches the value of the
and the ST_REST start output is deactivated.
Restore delay time
before the RESTORE output is activated, the reset timer is activated.
Reset delay time
1MAC309294-MB F
Restore start Val
setting, the RESTORE output
setting, the timer resets
RER620
Technical Manual