Circuit Breaker Failure Protection
115
7SS52 V4 Manual
C53000-G1176-C182-3
5.3.2 Setting Notes
I> BF The parameter I> BF (118/CU) is used to set the threshold I
d
/I
n
at which the pro-
tection detects a breaker failure and/or resets a TRIP command.
Siemens recommends to set this parameter to about 50 % of the smallest short-circuit
current to be expected.
STAB FAC:BF The parameter STAB FAC:BF (6201/CU) is used to match the stabilizing factor for
the selective breaker failure protection and the check zone to the service conditions.
A setting value of 0.25 is recommended for the stabilization against current transform-
er errors.
This parameter is only relevant for the modes BZ unbalance and trip rep/un-
bal. These modes are set with the parameter BF OP MODE (XX15/CU) (Chapter
5.3.6, page 128).
I> BF-EF The parameter I> BF-EF (XX19/CU) is used to set for an earth fault the threshold
I
d
/I
n
at which the protection detects a breaker failure and/or resets a TRIP.
Is< BF - EF The parameter Is< BF.EF (6202A/CU) is used to set the stabilizing current
threshold I
s
/I
no
for the breaker failure protection in the presence of an earth fault.
The setting of the parameter depends on the maximum stabilizing current to be ex-
pected and on the behaviour of the CTs.
This parameter is only displayed if the parameter EF charact. (6320A/CU) is set
to released.
With setting 0.00 the characteristic will not be used.
Note
Please note that the limit value I> BF must not be set smaller than the limit value Id>
SUPERV BZ (6308/CU). Otherwise, there is a risk of spurious tripping if there is an
operational differential current (e.g. fault in transformer circuit) and a binary input of
the breaker failure protection is activated simultaneously.
Note
This parameter is also used for the functions “End Fault Protection“ (Chapter
5.4, page 135) and “Current-Controlled TRIP Reset“ (Chapter 5.9.1, page
167).
Note
This parameter is also used for the functions “End Fault Protection“ (Chapter
5.4, page 135), “Current-Controlled TRIP Reset“ (Chapter 5.9.1, page 167).
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