Function - Siemens 3UG4 User Manual

3RR2 current monitoring relays
4.4 3RR21 current monitoring relays
4.4.2

Function

General functionality
Depending on the setting, the current monitoring relays monitor an AC load current that flows
through terminals 1/L1 - 2/T1 and 3/L2 - 4/T2 of the device for overshoot (I▲) or undershoot
(I▼) or in range monitoring (I▲ and I▼ ≠ OFF).
Depending on their design, the current monitoring relays are powered with a 24 V AC/DC or
24 to 240 V AC/DC supply voltage through terminals B1/B2.
With two-phase apparent current monitoring, one changeover output, and analog
adjustment, the 3RR214.-.A.30 (basic-version) current monitoring relays provide a high level
of monitoring reliability particularly in the rated and overload ranges.
The switching states of the output relay are given below in the section entitled "Function
diagrams."
Cable break detected
①
②
③
Image 4-1
If a cable break (zero current in branch circuit 1/L1 - 2/T1 or 3/L2 - 4/T2) is detected (time
①
), all running delay times are aborted, the red FAULT LED flashes rapidly and the CO
contact immediately changes its switching state.
When a defined current flow returns to both branch circuits (1/L1 - 2/T1, 3/L2 - 4/T2) (time
②
), the CO contact responds according to the defined settings.
If Memory = I, the tripping state is saved.
If the unmonitored phase 5/L3 - 6/T3 fails, this can be detected if a motor is connected by an
increase in current in both phases 1/L1 - 2/T1 and 3/L2 - 4/T2.
54
Cable break detected
No cable break
Hysteresis cable break:
- S00: 1.2 A to 1.6 A
- S0: 3.0 A to 4.0 A
- S2: 6.0 A to 8.0 A
Diagram of cable break
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004