Siemens SENTRON - Page 65

Selectivity with parallel incoming feeders
5.3 Selectivity with bus-couplers
Selectivity for 3VA molded case circuit breakers
Configuration Manual, 08/2016, A5E03603181010-01
65
① Total short-circuit current
Figure 5-4 Selectivity with an outgoing feeder short-circuit in the center busbar section
The displacement factor of the tripping characteristics K
t-I
is as follows:
With a total short-circuit current = 45 kA and
the partial short-circuit currents of all of the circuit breakers Q1 - Q5 = 15 kA,
the displacement factor K
t-I
= 3
The tripping characteristics of all of the instantaneous releases are far to the right of the total
short-circuit current in the case of circuit breakers Q1 - Q5 and are therefore not shown in
the diagram.
Protective response
Fuse F1 trips selectively, the contacts of circuit breakers Q1 - Q5 remain closed.