ABB RELION 620 Series Technical Manual page 270

Section 4
Protection functions
264
GUID-7B0FC64E-8C0B-4742-8252-522B91EFC4BC-ANSI V1 EN
Figure 121: Functional module diagram
Level detector 1
This module compares the phase currents (RMS value) to the Pickup value setting. The
Operation mode setting can be used to select the "Three Phase" or "Single Phase" mode.
If in the "Three Phase" mode all the phase current values are less than the value of the
Pickup value setting, the condition is detected and an enabling signal is sent to the timer.
This signal is disabled after one or several phase currents have exceeded the set Pickup
value value of the element.
If in the "Single Phase" mode any of the phase current values are less than the value of the
Pickup value setting, the condition is detected and an enabling signal is sent to the timer.
This signal is disabled after all the phase currents have exceeded the set Pickup value value
of the element.
The protection relay does not accept the Pickup value to be smaller than
Current block value.
Level detector 2
This is a low-current detection module that monitors the de-energized condition of the
protected object. The module compares the phase currents (RMS value) to the Current
block value setting. If all the phase current values are less than the Current block value
setting, a signal is sent to block the operation of the timer.
Timer
Once activated, the timer activates the PICKUP output and the phase-specific PICKUP_X
output. The time characteristic is according to DT. When the operation timer has reached
the value set by Trip delay time, the TRIP output and the phase-specific TRIP_X output
are activated. If the fault disappears before the module trips, the reset timer is activated.
1MAC504801-IB E
620 series ANSI
Technical Manual