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2 Functions
88
7ST6 Manual
E50417-G1176-C251-A3
Figure 2-19
Pick-up and tripping logic of the backup O/C protection
2.5.3
Setting Notes
General
The emergency overcurrent protection is only effective and accessible if address
127
FCT Emerg. O/C
has been set to
Enabled
during the configuration of the functional
scope. If the function is not required,
FCT Emerg. O/C
=
Disabled
is to be set.
In order to be effective, the emergency overcurrent protection function must also be
switched
ON
in address
2701
Emerg. O/C
. The emergency overcurrent protection
operates independently of other protection functions. It is automatically activated
when the distance protection is not operative. In address
2701
the time overcurrent
protection can also be switched
OFF
.
In case of switching onto a fault, the protection should trip instantaneously. To do so,
set in address
2702
SOTF Emerg. O/C
=
YES
. If the pickup threshold is exceeded
when switching onto a fault, the delay time set for the function is bypassed, and the
emergency overcurrent protection issues an instantaneous trip command.
The emergency time overcurrent protection can be blocked by the inrush restraint
feature if
Inrush O/C BU
=
YES
is set in address
2303
. The default setting for this
parameter is
Inrush O/C BU
=
NO
.
When the inrush restraint is activated, at least one power system cycle must elapse
after fault inception before the pickup signal of the emergency overcurrent protection
can be generated.
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