Functions
114
7SS52 V4 Manual
C53000-G1176-C182-1
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 protection
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 126).
EF charact. The parameter EF charact. (6320A/CU) is used to match the busbar and breaker fail-
ure protection to the system conditions and to the treatment of the starpoint. An expla-
nation of the standard characteristic and of the earth fault characteristic is given on
page 95.
With the setting blocked single-pole and multipole faults are treated with the same
characteristic.
With the setting released the measuring system switches to the more sensitive char-
acteristic in the presence of a 1-pole fault. This characteristic has a lower diff-current
threshold, which is set with the parameters Id> BZ - EF
(6109A/CU) or Id> CZ - EF (6111A/CU), and a stabilizing current threshold which
is set with the parameters Is< BZ - EF (6108A/CU) or Is< CZ - EF (6110A/CU).
The setting released enables also the marshalling of the binary input annunciation
for characteristic switchover ">EF charact.“ (FNo. 10478/CU).
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.
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 danger of spurious tripping. If there is
an operational differential current (e.g. defect in the transformer circuit) and at the
same time a binary input of the breaker failure protection is activated.
Note
This parameter is also used for the functions “End Fault Protection“ (Chapter
5.4, page 132), “Current-Controlled TRIP Reset“ (Chapter 5.9.1, page 165).
Note
This parameter is also used for the functions “End Fault Protection“ (Kapitel
5.4, Seite 132), “Current-Controlled TRIP Reset“ (Kapitel 5.9.1, Seite 165).
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