ABB Relion 620 Series, Technical Manual

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If a drop-off situation occurs, that is, voltage restores above
Voltage start value,
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
Recovery time 1… Recovery time 10 and Voltage level 1… Voltage level
10. The number of coordinates required to define a LVRT curve is set by Active
coordinate settings.
When
Recovery time 1 is set to non-zero value, it results into horizontal
characteristics from point of fault till
Recovery time 1.
Two examples of LVRT curve are defined in
Figure 359
and
Figure 360
with
corresponding settings in
Table 647
.
It is necessary to set the coordinate points correctly in order to avoid
maloperation. For example, setting for
Recovery time 2 should be greater
than
Recovery time 1. Recovery time 1… Recovery time 10 are the
respective time setting from the point of fault.
Figure 359: Low voltage ride through example curve A
Figure 360: Low voltage ride through example curve B
1MRS757644 H Protection functions
620 series
Technical Manual
689