13.2.5.2 Installation specications
Note
Please ensure strict adherence to the installation specications for live cables.
WARNING
Open-circuit voltage may result in death, serious injury or material damage
The current transformer output is a constant current power supply. In accordance with U = R * I,
the output voltage increases with an increasing resistance. If the connecting terminals of the
current transformer are open, the output voltage may become high enough for you to put your
life at risk or permanently damage the current transformer.
Avoid operating the unit when open. Operating a network for monitoring safely and without
faults requires that the monitoring relay and the 3UL23 residual current transformer have been
installed completely. It is absolutely necessary to short-circuit previously installed
3UL23 residual current transformers when the units are not connected to a monitoring relay.
3UL23 residual current transformer conductor cross-sections
In accordance with DIN EN 60204‑1 "Safety of machinery", the current carrying capacity of
conductors is limited depending on their cross-section. This results in the ideally suitable
residual current transformer to be used as per the following table. Please observe potentially
deviating, local installation specications.
Order number Bushing opening
Diameter [mm]
Max. conductor cross-
section
3P copper cable + N
[mm
2
]
AWG [kcmil] Rated current per
phase [A]
3UL2302-1A 35 25 4 85
3UL2303-1A 55 50 1 / 0 150
3UL2304-1A 80 150 300 225
3UL2305-1A 110 240 500 400
3UL2306-1A 140 2 x 185 2 x 350/400 500
3UL2307-1A 210 2 x 240 2 x 500 630
3UL23 residual current transformers for external fault current monitoring
All live cables must be routed as close to the center of the transformer as possible.
Any neutral conductor must be routed through the transformer. Grounded protective
Accessories
13.2 Accessories for 3UG4 monitoring relays
SIRIUS 3UG4 / 3RR2 monitoring relay
Equipment Manual, 07/2021, NEB927043002000/RS-AD/005 251
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