Technical information

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1SDC210033D0202
Glossary
Performance Parameters
G2.1 Size
Term that indicates a group of circuit-breakers with phisical dimension common to a nominal
current size (same poles number).
G2.2 Rated uninterrupted current (In)
The rated uninterrupted current for a circuit-breaker is the current value, that the circuit-
breaker can carry during uninterrupted service.
G2.3 Rated service current (Ie)
Current value defined by the manufacturer, which takes into account the rated service volt-
age at the rated frequency, the rated service, the utilisation category and the type of protec-
tive casing, if any.
G2.4 Rated service voltage (Ue)
The rated service voltage of a device is the voltage value which, along with the rated current
value, determines the use of the device itself and which the applicable tests and utilisation
category refer to.
G2.5 Rated insulation voltage (Ui)
The rated insulation voltage of a device is the voltage value to which the dielectric tests and
surface insulation distances refer. In no case may the rated service voltage value exceed the
rated insulation voltage.
G2.6 Rated impulse withstand voltage (Uimp)
Peak value of an impulse voltage of given shape and polarity that the device can withstand
without faults under specified test conditions and to which the insulation clearances refer.
G2.7 Rated ultimate short-circuit breaking capacity (Icu)
The rated ultimate short-circuit breaking capacity of a circuit-breaker is the value of the
short-circuit current the circuit-breaker is able to break twice (according to the O – t – CO
cycle) at the corresponding rated operating voltage. The circuit-breaker is not required to
carry its rated current after the opening and closing cycle.
G2.8 Rated service short-circuit breaking capacity (Ics)
The rated service short-circuit breaking capacity of a circuit-breaker is the current value the
circuit-breaker is able to break three times according to a cycle of opening, pause and clos-
ing operations (O - t - CO - t - CO) at a given rated service voltage (Ue) and at a given power
factor. After this cycle, the circuit-breaker must be able to carry its rated current.
G2.9 Rated short-time withstand current (Icw)
The rated short-time withstand current is the current value the circuit-breaker can carry in
the closed position for a short time under specified conditions of service and behaviour. The
circuit-breaker must be able to carry this current for as long as the established delay time
lasts so as to guarantee selectivity among circuit-breakers installed in series.
G2.10 Rated short-circuit making capacity (Icm)
The rated short-circuit making capacity of a device is the value, declared by the manufacturer,
that coincides with the rated service voltage, the rated frequency and with a specified alter-
nating current power factor or direct current time constant. It is expressed as the maximum
peak value of the prospective current under specified conditions.
G2.11 Utilisation category of circuit-breakers
The utilisation category of a circuit-breaker must be established according to whether it is
specifically designed to achieve selectivity by means of an intentional delay or not, in relation
to other devices installed in series on the load side, under short-circuit conditions.
It’s possible to distinguish two user classes:
Class A - Circuit-breakers not specifically designed for selectivity under short-circuit condi-
tions in relation to other protection devices installed in series on the load side, i.e. without
intentional delay, applicable in short-circuit conditions and, therefore, without specification of
the short-time withstand current.