Selectivity for 3VA molded case circuit breakers
Configuration Manual, 08/2016, A5E03603181010-01
75
Glossary
Coupler circuit breaker
Current-limiting circuit breaker
According to EN 60947-2, a current-limiting circuit breaker is a "circuit-breaker with a break-
time short enough to prevent the short-circuit current reaching its otherwise attainable peak
value".
Delay time t
ZSI
Defined non-operation time of all circuit breakers that detect a short-circuit current and/or a
ground fault current and do not receive a "block" signal when Zone Selective Interlocking
(ZSI) is activated.
Grading time
Grading times are the intervals required between the delay times of individual circuit
breakers in order to achieve time selectivity.
Ground fault
An unintentional electrically conducting connection, potentially caused by an arc, between an
outer conductor or a normally isolated neutral conductor to ground or to grounded
components.
Ground fault current
Current resulting from a ground fault due to a fault or an incorrect connection in an electric
circuit
I release
Instantaneous electromagnetic over-current release for instantaneous short-circuit protection
in the event of a dead short-circuit
I
2
t value
The I
2
t value is the thermal value of a prospective or a limited short-circuit current (let-
through current).
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