Selectivity for 3VA molded case circuit breakers
Configuration Manual, 08/2016, A5E03603181010-01
7
Introduction
1
There are growing demands in many sectors for more reliable, secure electricity supplies for
installations, whether these are data centers, airports, industrial production facilities, power
plants, etc. (Over-current) selectivity can make an important contribution to fulfilling these
demands. It is capable of minimizing the effects of a fault in terms of its duration and the
area it affects, thereby ensuring that plant sections that are not affected by the fault will
remain in operation.
This "Selectivity" Configuration Manual introduces you to the subject of selectivity and
describes the relevant implementation methods as well as the relationships between
selectivity and infeed and/or selectivity and undervoltage.
The manual is aimed at engineers, planners and project managers.
Please note that the principles of selectivity described in this manual apply only to low-
voltage switchboard and distribution systems.
Further information about implementing selectivity with 3VA molded case circuit breakers
can be found in the following documents:
● 3VA Manual (order number 3ZW1012-0VA10-0AB1)
● 3VA Communications Manual (order number 3ZW1012-0VA20-0BB0)
Structure of the manual
The manual is divided into the following chapters:
● Selectivity - terms, definitions a
nd methods (Page 9)
This chapter explains important terms relating to selectivity and presents possible
methods for implementing selectivity.
● Application examples (Page 13)
The metho
ds by which selectivity can be implemented using circuit breakers are
explained in greater depth and demonstrated by specific examples.
● Selectivity implemented by combinations
of protective devices (Page 47)
Conditions are demonstrated under which different protective devices can be combined in
order to afford selectivity.
● Selectivity with parallel incoming feed
ers (Page 57)
The effects of parallel incoming feeders on selectivity are explained.
● Selectivity and undervoltage protection (Page 69)
The bou
ndary conditions for implementing selectivity using circuit breakers equipped with
an undervoltage release are illustrated.
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