ABB RELION Series, Technical Manual

Page: 443 / 804

the set Start value df/dt value, the module reports the exceeding of the value to the
operate logic module.
The protection relay does not accept the set value "0.00" for the Start
value df/dt setting.
Operate logic
This module is used for combining different protection criteria based on the frequency
and the frequency gradient measurement to achieve a more sophisticated behavior of
the function. The criteria are selected with the
Operation mode setting.
Table 457: 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
1MRS758755 A
Section 4
Protection functions
REC615 and RER615 437
Technical Manual