ABB Relion 620 Series - Page 703

Table 662: Operation modes for operation logic
Operation mode Description
Freq< The function operates independently as the underfrequency
("Freq<") protection function. When the measured frequency
is below the set value of the Start value Freq< setting, the
module activates the START and STR_UFRQ outputs. The
time characteristic is according to DT. When the operation
timer has reached the value set by the Operate Tm Freq
setting, the OPERATE and OPR_UFRQ outputs are activated.
If the frequency restores before the module operates, the
reset timer is activated. If the timer reaches the value set
by the Reset delay Tm Freq setting, the operate timer resets
and the START and STR_UFRQ outputs are deactivated.
Freq> The function operates independently as the overfrequency
("Freq>") protection function. When the measured frequency
exceeds the set value of the Start value Freq> setting, the
module activates the START and STR_OFRQ outputs. The
time characteristic is according to DT. When the operation
timer has reached the value set by the Operate Tm Freq
setting, the OPERATE and OPR_OFRQ outputs are activated.
If the frequency restores before the module operates, the
reset timer is activated. If the timer reaches the value set
by the Reset delay Tm Freq setting, the operate timer resets
and the START and STR_OFRQ outputs are deactivated.
df/dt The function operates independently as the frequency gra-
dient ("df/dt"), rate-of-change, protection function. When
the frequency gradient exceeds the set value of the Start
value df/dt setting, the module activates the START and
STR_FRG outputs. The time characteristic is according to
DT. When the operation timer has reached the value set by
the Operate Tm df/dt setting, the OPERATE and OPR_FRG
outputs are activated. If the frequency gradient restores be-
fore the module operates, the reset timer is activated. If the
timer reaches the value set by the Reset delay Tm df/dt set-
ting, the operate timer resets and the START and STR_FRG
outputs are deactivated.
Table continues on the next page
1MRS757644 H Protection functions
620 series
Technical Manual
703