ABB RELION 620 Series Technical Manual page 708

Section 4
Protection functions
702
Table 662: Operation modes for operation logic
Operation mode
Freq<
Freq>
df/dt
Freq< + df/dt
Table continues on next page
Description
The function operates independently as the underfrequency
("Freq<") protection function. When the measured frequency is
Start value Freq< setting, the module
below the set value of the
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
Reset delay Tm Freq setting, the operate timer resets and
set by the
the START and STR_UFRQ outputs are deactivated.
The function operates independently as the overfrequency
("Freq>") protection function. When the measured frequency
exceeds the set value of the
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
Reset delay Tm Freq setting, the operate timer resets and
set by the
the START and STR_OFRQ outputs are deactivated.
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
module activates the START and STR_FRG outputs. The time
characteristic is according to DT. When the operation timer has
Operate Tm df/dt setting, the OPERATE
reached the value set by the
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
the operate timer resets and the START and STR_FRG outputs are
deactivated.
A consecutive operation is enabled between the protection
methods. When the measured frequency is below the set value of
Start value Freq< setting, the frequency gradient protection is
the
enabled. After the frequency has dropped below the set value, the
frequency gradient is compared to the set value of the
dt setting. When the frequency gradient exceeds the set value, the
module activates the START and STR_FRG outputs. The time
characteristic is according to DT. When the operation timer has
Operate Tm df/dt setting, the OPERATE
reached the value set by the
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
the operate timer resets and the START and STR_FRG outputs are
deactivated. The OPR_UFRQ output is not active when this operation
mode is used.
1MRS757644 F
Start value Freq> setting, the module
Start value df/dt setting, the
Reset delay Tm df/dt setting,
Start value df/
Reset delay Tm df/dt setting,
620 series
Technical Manual