ABB REF615 L - Load shedding and restoration LSHDPFRQ

Table 422: 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 gradient ("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
before the module operates, the reset timer is
activated. If the timer reaches the value set by
the
Reset delay Tm df/dt setting, the operate
timer resets and the START and STR_FRG
outputs are deactivated.
Table continues on next page
Section 4 1YHT530004D05 D
Protection functions
496 615 series
Technical Manual