Installation Faults - Siemens 3UG4 User Manual

13.2.5.4

Installation faults

For reasons of clarity, the representations show only the residual current transformer with
the currents passing through it rather than the complete residual current monitoring unit and
residual current transformer. If the vectorial sum of the currents passing through the residual
current transformer does not equal zero, part of the current is bypassing the transformer to
ground and the residual current monitoring relay triggers a warning or an alarm if the current
is correspondingly high.
In some instances, false alarms may occur for no apparent reason. However, these
represent installation faults.
The following examples demonstrate the most common installation faults.
Parallel connections of conductors
If several residual current monitoring relays are installed in one network, a conductor routed
through several residual current transformers must not be connected to itself downstream of
the transformer, as this would effectively represent a parallel connection of the conductor.
This fault occurs particularly often with neutral conductors. This fault causes the currents to
be distributed across the conductor. This means that the current flowing through the load to
be monitored is no longer 100 % of the total current and all integrated monitoring relays
measure fault currents.
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004
13.2 Accessories for 3UG4 monitoring relays
Accessories
341