IT system applications of 3VA molded case circuit breakers

The main advantage of IT systems is that they safeguard continuity of service by electrical installations and are therefore deployed predominantly in consumer installations where availability of electrical power is a priority. As a general rule, circuits are interrupted only if two insulation faults occur simultaneously.

Preferred applications for IT systems are therefore:

The IT system is a low-voltage power supply network with increased failure-safety in the event of ground faults. In an IT system, live phases are not connected to ground. A ground fault does not cause system shutdown. DIN EN 60204‑1 (VE 0113) therefore stipulates that an insulation monitoring device must be installed in order to indicate ground faults. In the unusual event that a fault on the load side coincides with a second fault on the line side, the full phase-to-phase voltage is connected across one contact of the breaker. Siemens 3VA molded case circuit breakers for line protection, whether they are equipped with a thermal-magnetic trip unit or an electronic trip unit, are suitable for use in IT systems.

Accordingly, the molded case circuit breakers meet the requirements of standard IEC / DIN EN 60947‑2 Annex H up to a maximum voltage (Ue, max.) of 690 V AC.