Siemens 3UG4 User Manual page 158

3UG4.1 line monitoring relay
6.7 3UG4617 / 3UG4618 line monitoring relays
Monitoring
Output relay K1 is for warning or shutdown on faults in the power system (voltage,
asymmetry). Output relay K2 responds differently depending on the phase sequence.
Phase sequence
If the correct phase sequence is applied to terminals L1-L2-L3, output relay K2 (relay contact
21-22-24) picks up. This is represented by a relay symbol on the display. If the phase
sequence is incorrect, output relay K2 will not pick up. An error is not indicated on the
display; only the relay symbol remains in the disconnected state.
Undervoltage or overvoltage
If the monitored voltages (Ux-y) are larger than the set lower voltage value (U▼) and smaller
than the set upper voltage value (U▲), i.e. they are within the voltage limits and the line
voltage asymmetry (Asy) is less than the set value, the output relay K1 (relay contact
11-12-14) picks up approx. 50 ms after the response of output relay K2 (relay
contact 21-22-24).
The display indicates the following voltages in the case of the line monitoring relays:
● 3UG4617: Line-to-line voltage between L1 and L2, L1 and L3, L2 and L3
● 3UG4618: Line-to-neutral voltage between L1 and N, L2 and N, L3 and N
Phase failure
In the case of a phase failure (or neutral conductor failure for the 3UG4618 line monitoring
relays), output relay K1 (relay contact 11-12-14) drops out without delay to protect the
application from any damage that may result. Set delay times have no effect on phase failure
monitoring.
In the case of voltage undershoot, voltage overshoot, or asymmetry overshoot faults, output
relay K1 drops out after the set tripping delay time (Del).
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 80 % from the load in
the case of regenerative power recovery.
158
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004