User Manual

Accessories
14.2 Accessories for 3UG4 monitoring relays
3UG4 / 3RR2 monitoring relays
328 Manual, 02/2013, NEB927043002000/RS-AA/002
b) A solid shield sleeve, e.g. turned from a normal, low-carbon tool steel must be
precisely in contact with the internal ring of the residual current transformer. The wall
thickness of the sleeve must be 1 mm at minimum, the length of the sleeve (L) must
correspond to the internal diameter of the transformer used.
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① Phase (and neutral conductor)
② Shield sleeve
③ Residual current transformer
14.2.5.4 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.