Siemens 3UG4 User Manual page 342

Accessories
13.2 Accessories for 3UG4 monitoring relays
Mixing up conductors
In a network with several loads there is the risk that active conductors of loads that are to be
separately monitored for fault currents can get mixed up. This fault leads to false tripping as
the inflowing and outflowing currents are not always exactly the same strength, even if the
loads are identical.
342
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004