9.3.2 Functions
General functionality
The 3UG4581 insulation monitoring relays are supplied with a rated control and supply voltage
of 24 V to 240 V AC/DC, and they monitor the insulation resistance in ungrounded AC systems
in accordance with IEC 61557‑8.
The devices can monitor control circuits (1-phase) and main circuits (3-phase). For this purpose,
the insulation resistance between the system cables (terminal L) and system ground (terminal
) is measured. Systems with rated system voltages U
n
= 0 to 400 V AC (50 to 60 Hz) can be
connected directly to the measuring inputs, and their insulation resistance can be monitored.
The 3UG4581 insulation monitoring relays have two rotary buttons for adjusting the insulation
resistance R and a test/RESET button for performing an internal test on the device, or for
resetting the device.
If the measured value drops below the set threshold, the output relays are set to fault status.
For systems with voltages over 400 V AC, the 3UG4583 insulation monitoring relays with
3UG4983 voltage reducer module can be used for system voltages to 690 V AC.
You will nd the adjustment ranges and factory settings of the available parameters in Chapter
"Operator control (Page 163)".
You will nd a description of the individual parameters in the Chapter "Parameters (Page 281)".
Measuring procedure of the 3UG4581 insulation monitoring relay
An overlaid DC measuring signal is used on the 3UG4581 insulation monitoring relay for
measuring. The insulation resistance of the system is calculated with the help of the overlaid DC
measuring voltage and the resulting current.
The 3UG4581 insulation monitoring relays can be congured to the relevant application
conditions and are therefore versatile in use.
Monitoring
The system to be monitored is connected to terminal L (connection to phase or N conductor).
The ground potential is connected to terminal .
The devices work according to the closed-circuit principle NC.
After applying the rated control and supply voltage, the insulation monitoring relay goes
through an internal test that checks the proper functioning of the operational device. The test
encompasses an internal test of the device at hardware and rmware level, as well as system
diagnostics with calculation of the rst measured value of the insulation resistance. If there are
no internal device faults or external faults on completion of this test, output relay K1 picks up.
This test can take several seconds depending on individual system properties.
3UG458. insulation monitoring relay.
9.3 3UG4581 insulation monitoring relay
SIRIUS 3UG4 / 3RR2 monitoring relay
Equipment Manual, 07/2021, NEB927043002000/RS-AD/005 159
To Next Page
Loading...
