ABB RELION REX640 Technical Manual page 902

Protection functions
When the
component is compared with the set
Voltage start value , the START output is activated.
Once START is activated, the function monitors the behavior of the voltage defined
Voltage selection setting with the defined LVRT curve. When defined voltage
by
enters the operating area, the OPERATE output is activated instantaneously. The
pulse length of OPERATE is fixed to 100 ms. START also deactivates along with
OPERATE.
If a drop-off situation occurs, that is, voltage restores above
before OPERATE is activated, the function does not reset until maximum recovery
time under consideration has elapsed, that is, START output remains active.
LVRT curve is defined using time-voltage settings coordinates. The settings
available are
10 . The number of coordinates required to define a LVRT curve is set by Active
coordinate settings.
Two examples of LVRT curve are defined in
corresponding settings in
Figure 504: Low voltage ride through example curve A
902
Voltage selection setting is "Positive Seq", the positive-sequence
Recovery time 1 ... Recovery time 10 and Voltage level 1 ... Voltage level
Recovery time 1 is set to non-zero value, it results into horizontal
When
characteristics from point of fault till
Table 853
It is necessary to set the coordinate points correctly in order to avoid
maloperation. For example, setting for
than Recovery time 1 . Recovery time 1 ... Recovery time 10 are the
respective time setting from the point of fault.
Voltage start value . If it is lower than the set
Recovery time 1.
Figure 504
and
.
Recovery time 2 should be greater
1MRS759142 F
Voltage start value ,
Figure 505
with
REX640
Technical Manual