Siemens 3UG4 - Page 198

3UG4625 residual current monitoring relay with 3UL23 transformer
8.3 Functions
3UG4 / 3RR2 monitoring relays
198 Manual, 05/2016, NEB927043002000/RS-AC/004
Tripping conditions
The combination of 3UG4625 residual current monitoring relay and 3UL23 residual current
transformer responds according to the following tripping conditions:
Residual current monitoring relays
Fault current
No tripping
0 to 85 % of the set threshold
Tripping not defined 85 to 100 % of the set threshold
Tripping
>= 100 % of the set threshold
3UL23 residual current transformer
3UL23 residual current transformers can be used in conjunction with 3UG4625 residual
current monitoring relays to detect fault currents in machines and systems.
3UL23 residual current transformers are suitable for detecting pure AC fault currents and AC
fault currents with a pulsating direct-current component.
These necessary accessories are described in Chapter "3UL23 residual current transformers
for 3UG4625 monitoring relays (Page 333)."
Note
Do not ground the neutral conductor downstream of the residual current transformer as
otherwise fault current monitoring functions can no longer be ensured.