User Manual

3UG4.1 line monitoring relay

6.3 3UG4512 line monitoring relay

3UG4 / 3RR2 monitoring relays

Manual, 02/2013, NEB927043002000/RS-AA/002

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 101)."

Reset response

The device features an autoreset function. The autoreset function resets the output relay to

its original state after an error message and rectification of the fault that has occurred.

Note

The red "phase failure / phase sequence" LED is a fault diagnostics display and does not

indicate the current state of the relay!