Siemens SENTRON - Implementation of Total Selectivity

Methods of implementing selectivity using circuit breakers
3.4 Time selectivity
Selectivity for 3VA molded case circuit breakers
28 Configuration Manual, 08/2016, A5E03603181010-01
3.4.3 Implementation of total selectivity
If the upstream circuit breakers used have a sufficiently high rated short-time withstand
current (I
cw
) or an instantaneous short-circuit release with a sufficiently high setting, high
values for the selectivity limit current (I
s
) can be achieved. Total selectivity can be
implemented if the instantaneous I release can also be disabled or if the breaker features an
instantaneous short-circuit release with a sufficiently high setting.
The following Siemens circuit breakers are used to implement total selectivity in the following
example:
● Q1, Q2, Q3: SENTRON 3WL air circuit breakers with rated short-time withstand
current (I
cw
):
– up to 100 kA for a duration of 400 ms
– The values for rated ultimate short-circuit breaking capacity (I
cu
) and rated short-time
withstand current (I
cw
) are very similar
● Q4: SIRIUS 3RV circuit breaker
The instantaneous I release on circuit breakers Q1 and Q2 is disabled.