Selectivity implemented by combinations of protective devices
4.1 Molded case circuit breakers and downstream fuse
Selectivity for 3VA molded case circuit breakers
Configuration Manual, 08/2016, A5E03603181010-01
49
Circuit breaker with an S release
In order to ensure selective interruption of short-circuits when circuit breakers with delayed
short-circuit release are used, the safety margin between the lower tolerance value t
sd-u
of
the S release delay time and the upper tolerance band t
S-O
of the time-current characteristic
must be at least about 100 ms.
① Dynamic selectivity zone
② Tripping characteristic
③ Time-current characteristic
Further information
The characteristics for Siemens 3NA LV HRC fuses can be found in the Configuration
Manual "Fuse Systems", order number 3ZW1012-3NW10-0AB1.
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