2 Functions
266
7SD5 Manual
C53000-G1176-C169-1
Figure 2-116
Logic diagram of the high current switch on to fault protection
2.13.2 Setting Notes
General
A precondition for the use of the switch-onto-fault overcurrent protection function is
that the configuration of the device functions (Section 2.1.1) has been configured in
address
124
HS/SOTF-O/C
=
Enabled
. At address
2401
FCT HS/SOTF-O/C
it can
also be switched
ON
or
OFF
.
I
>>> Stage
The magnitude of fault current which leads to the pickup of the
I
>>> stage is set as
I>>>
in address
2404
. This stage is active only during the connecting of the local end
while the circuit breakers at all other ends of the protected object are open. Choose a
value which is high enough for the protection not to pick up on the RMS value of the
inrush current produced during the connection of the protected object. On the other
hand, fault currents flowing through the protected object need not be considered.
When using a PC and DIGSI
®
to apply the settings, these can be optionally entered
as primary or secondary values. If secondary quantities are used, all currents must be
converted to the secondary side of the current transformers.
I
>>>> Stage
The
I
>>>> stage (address
2405
) works regardless of the circuit breaker position.
Since it trips extremely fast it must be set high enough not to pickup on a fault current
flowing through the protected object. This means that it can be used only if the protect-
ed object allows current grading, as is the case with transformers, series reactors or
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