Siemens 3UG4 User Manual page 194

3UG4625 residual current monitoring relay with 3UL23 transformer
8.3 Functions
To ensure a maximum plant availability 3UG4625 residual current monitoring relays focus on
the following features:
● High degree of measuring accuracy
3UG4625 residual current monitoring relays in combination with 3UL23 residual current
transformers operate with a measuring accuracy of -7.5 %/+7.5 %. This enables set limit
values to be monitored very precisely. False tripping caused by measuring errors is
minimized.
● Adjustable delay times
The ON-delay time of 3UG4625 residual current monitoring relays can be configured
freely, enabling fading out of fault currents due to high input currents that are measured
during motor start-up only. Short-term fault currents or emitted interference can be easily
faded out using the adjustable tripping delay time. For more information please see the
Chapter "Measuring accuracy (Page 193)".
● Wide-range supply voltage
3UG4625 residual current monitoring relays can be operated at an input voltage of
between 24 and 240 V AC/DC. This not only ensures that devices can be used
worldwide, but that temporary supply voltage dips do not cause a failure of the monitoring
function, that is, plant stoppage.
you intend to continue plant operation even if the monitoring function fails. This means
only actively determined fault currents are reported via the relay outputs.
● Permanent self-monitoring
The permanent self-monitoring feature of 3UG4625 ensures reliable system monitoring.
The connected 3UL23 residual current transformer is also permanently monitored for
open-circuit or short-circuit. As a result, cyclic manual tests to ensure its function are
obsolete. Regardless of this, it is possible at any time to test the output relays for
switching capability. Pressing the Set button for longer than 2.5 s will call up parameter
assignment mode. This will cause the output relays to switch to the fault state as a safety
precaution. Proceed as described above to quit parameter assignment mode. The output
relay will once again switch back to its normal operating state.
Measuring accuracy
The combination of 3UG4625 residual current monitoring relay and 3UL23 residual current
transformer is designed so that a warning or alarm is triggered at the latest upon exceeding
the set limit values. To safeguard this function, slightly higher fault currents than those
actually measured are displayed and compared with the set limit values.
The measuring accuracy is -7.5 %/+7.5 % of the value displayed. This takes into account the
measuring accuracy of monitoring relay and residual current transformer.
194
The switching response of the relay outputs can be set to open-circuit principle (NO) if
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004