Selectivity Between Abb Sace Circuit-Breakers - ABB SACE Emax 2 Series Operating Instructions Manual

5 - Selectivity between ABB SACE circuit-breakers

Foreword It is possible to obtain selectivity between ABB SACE circuit-breakers (including Emax 2).
Types of selectivity With ABB SACE electronic trip units selectivity can be:
Further documents For each type of selectivity, the protections must be set so that only those circuit-breakers capable of
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There is selectivity in an installation when, in the event of an overload or short-circuit, it is possible to
identify and isolate the point of overload or fault by opening only some circuit-breakers to guarantee
service continuity to the installation.
NOTE: selectivity is recommended in all installations with multiple switchgears or circuit-
breakers connected, for example cascading or in a tree (with a main circuit-breaker on the
supply side, and other circuit-breakers downstream to protect areas on the other side).
Thus, only the circuit-breaker immediately upstream the overload or fault trips, and avoids
opening of the circuit-breakers further upstream.
• Current-based selectivity, activated in the event of over-current, and in which the protections of
the trip units are set with different current thresholds, based on the principle the closer the fault
point is to the power supply the greater the current will be.
• Time selectivity, activated in the event of a short-circuit in which the S protection normally trips,
and in which the protections of the trip units are set with different tripping times, so that with
cascading circuit-breakers the circuit-breakers further downstream open before those further
upstream.
• Time-current selectivity, which is a combination of the previously mentioned types, and in which
the protections of the trip units are set so that the tripping times and current thresholds increase
with proximity to the power supply.
• Energy selectivity, which uses current-limiting circuit-breakers, characterized by extremely short
tripping times in the event of a short-circuit to avoid the current reaching the peak value (in the
case of ABB SACE circuit-breakers, for example, all the moulded-case circuit-breakers of the Tmax
series and certain air circuit-breakers of the Emax series are limiters).
• Zone Selectivity, which is an evolution of time selectivity, and in which is a dialog created between
the trip units by means of output and input blocking signals. For more information on Zone
Selectivity with ABB SACE circuit-breakers and in particular Emax 2, see the chapter "1 - Zone
Selectivity" starting on page 138.
isolating the overload or fault open, without the rest of the installation being de-energized. Relevant
definitions, operating principles, areas of application, advantages and disadvantages, requirements,
indications for setting the protections and examples are provided in the Technical Application Paper QT1
1SDC007100G0205 Low voltage selectivity with ABB circuit-breakers
Circuit-breakers E1.2-E2.2-E4.2-E6.2
5 - Selectivity between ABB SACE circuit-breakers
ABB | SACE Emax 2