Residual Current Devices; Portfolio - Siemens 3VA1 100 A Manual

4.8

Residual current devices

Residual current devices afford fault protection (formerly referred to as: protection in case of
indirect contact) and supplementary protection (formerly referred to as: protection in case of
direct contact) in low-voltage systems. In the event of a basic insulation failure or direct
contact with live components, they provide some degree of protection to persons, material
assets and livestock against harm.
Operating principle of a residual current device
In fault-free electrical installation, the vector sum of the load currents of all connected
conductors equals zero. A residual current occurring in the protected circuit as the result of
an insulation fault, for example, induces a voltage in the secondary winding of a summation
current transformer. The evaluation electronics system monitors the induced voltage and
transmits a trip command to the RCD trip unit if the trip criterion is fulfilled. The molded case
circuit breaker with residual current protection combination is designed to ensure that the
molded case circuit breaker contacts open if the residual current exceeds a preset value.
4.8.1

Portfolio

The new portfolio of residual current devices includes three different RCD designs so that an
optimum solution is available for every conceivable type of application:
● Side mounted
● Loadside
● Modular
Since all residual current devices can be set to between 0.03 A and maximum 5 A or 30 A,
they are suitable for use in the following applications:
● Personnel protection: I
Note
In order to protect personnel, it is necessary to seal the transparent protective cover so
that the 30 mA setting range cannot be changed.
● Fire protection: I
● Protection in the case of indirect contact
● Ground-fault protection
3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02
≤ 30 mA with instantaneous tripping
Δn
≤ 300 mA
Δn
Accessories
4.8 Residual current devices
293