Siemens SENTRON 3VL series - Use in IT Systems

Application planning
5.5 Use in IT systems
3VL IEC molded case circuit breakers
62 System Manual, 11/2013, 110 0110 - 02 DS 03
5.5
Use in IT systems
Use of the 3VL molded case circuit breakers in IT systems
The 3VL molded case circuit breakers up to size VL1250 have been tested in accordance
with IEC / EN 60947-2, Annex H (testing sequence for molded case circuit breakers for IT
systems) up to a maximum voltage (U
i
max.) of 690 V AC. The 3VL8 and 3VL7 (1250 A)
cannot be used in an IT system.
The 3VL molded case circuit breakers for system protection from SIEMENS, optionally
available with thermal overload and electromagnetic short-circuit releases, or electronic trip
units, are suitable for use in IT systems. The molded case circuit breakers also meet the
requirements of IEC 60947-2 Annex H (EN 60947-2, Annex H). The respective options are
required here, and the necessary safety clearances (ventilation clearances) must be
observed.
Selection criteria for molded case circuit breakers
The devices are always dimensioned and selected independently of the relevant system
type. The circuit breaker is always selected in accordance with the maximum short-circuit
current in the IT system. The device is selected in accordance with the relevant I
cu
values of
the 3VL molded case circuit breaker. The neutral conductor is not grounded by definition in
the IT system.
The system operator ensures that no double ground fault can occur on the input or output
side of the molded case circuit breaker. In this case, the switching capacity of the IT systems
remains unchanged.
If this is not guaranteed, the values in accordance with the standard IEC 60947-2 Annex H
apply for single-pole short-circuits.