3UG4.1 line monitoring relay
6.3 3UG4512 line monitoring relay
3UG4 / 3RR2 monitoring relays
112
Manual, 05/2016, NEB927043002000/RS-AC/004
6.3.2
Function
General functionality
The 3UG4512 line monitoring relays monitor the phase sequence and the phase failure of
one of the three phases in a three-phase system. The asymmetry threshold is 10 %.
The devices are self-powered (measuring voltage = rated control supply voltage) and work
on the closed-circuit principle. The 3UG4512 line monitoring relays monitor all phases of
three-phase AC networks from 160 to 690 V through terminals L1 / L2 / L3 and also draw
power from all three phases simultaneously.
All 3UG4512 line monitoring relays feature at least one output relay (output relay K1 CO
contact). The 3UG4512-.B line monitoring relays have an additional relay (output relay K2
CO contact). Output relay K2 switches synchronously with output relay K1.
No settings are required for operation.
Note
The specified voltages represent the absolute thresholds.
Monitoring
Thanks to a special measuring method, a phase failure is detected with certainty despite
wide-range voltage from 160 to 690 V AC and reverse power of up to 90 % from the load in
the case of regenerative power recovery.
If the line voltage is switched on, the LED "coil symbol" will light up green. If the correct
phase sequence is applied to terminals L1-L2-L3, the output relays pick up. If the phase
sequence is incorrect, the "phase failure / phase sequence" LED flashes red and the output
relays remain in their quiescent position. On a phase failure, the "phase failure / phase
sequence" LED lights up red continuously and the output relays drop out to protect the
application from any damage that may result.
You will find the switching states of the output relays below in section "Function diagrams"
and in Chapter "Diagnostics (Page 114)."