Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 142)

Circuit breakers as disconnectors
See also Section 2.2.1.1 . Circuit breakers often fulfill the disconnector requirements and
therefore can be used as such. Such circuit breakers with disconnector properties must be
correspondingly tested and marked with the disconnector symbol.
Fig. 4.2-7
Switch symbol for circuit breakers with disconnector function. The horizontal line symbolizes the
disconnector properties, the cross stands for the circuit breaker function.
Circuit breakers as main switches (supply disconnector devices)
See also Section 2.2.1.5 .
Under IEC 60204-1, circuit breakers are expressly authorized as main switches insofar as they
possess disconnector properties.
Circuit breakers as EMERGENCY STOP switches
See also Section 2.2.1.6.
According to IEC 60204-1, supply disconnect switches are permitted as EMERGENCY STOP
devices if they are easily accessible for the operating personnel. For use as an EMERGENCY
STOP switch the handle must be red on a yellow background.
4.2.2.5 Installation of circuit breakers, safety clearances
See also Section 2.3.9 .
Circuit breakers can cope with very high currents at high voltages when breaking short-circuits.
During the breaking process, the contact systems and arcing chambers consequently convert
large amounts of power into heat energy. In addition to high temperature rises of components
such as contacts, de-ion plates and walls of the contact chambers, the energy converted into an
arc results in heating of the air in the contact system to several thousand degrees Celsius and
hence to the formation of a conductive plasma. This plasma is usually emitted through blow-out
openings to the outside and must not reach any conductive parts to prevent secondary short-
circuits.
For this season, safety clearances are specified for circuit breakers ( Fig. 4.2-8 ), within which no
conductive parts – for example metallic walls or uninsulated conductors – may be located.
Frequently additional insulation components (phase partition walls or covers; in some cases
optional) are used. With some products, additional insulation of the connected conductors is
required in accordance with manufacturer specifications. Non-compliance with the safety
clearances can result in accidents with most severe consequences.
Fig. 4.2-8
It is essential that the safety clearances are observed. No conductive parts may be located within the
hatched zones such as metallic walls or uninsulated conductors.
LVSAM-WP001A-EN-P - April 2009 4-34