3UG458. insulation monitoring relay
9.4 3UG4582/3UG4583 insulation monitoring relays
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004
239
Monitoring
The system to be monitored is connected to the measuring signal inputs L+, L-. The
terminals can be connected to any conductor (phase, +/- potential, or N conductor). The
measuring signal inputs must be connected to different conductors.
The ground potential is connected to the terminals
and KE.
KE stands for control ground and is used for monitoring the fault-free ground connection of
the insulation monitoring relay.
The 3UG4582 insulation monitoring relays work according to the closed-circuit principle NC.
The 3UG4583 insulation monitoring relays work in accordance with the set relay switching
behavior (closed-circuit principle NC or open-circuit principle NO).
After applying the rated control 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 firmware level (on the
3UG4583, a settings check is also carried out) , as well as system diagnostics with
calculation of the system discharge capacity of the first measured value of the insulation
resistance. If there are no internal device faults or external faults on completion of this test,
the output relays change their switching state (if closed-circuit principle is set). The time for
this test can be 10 s - 15 s with purely AC systems. The circuit is opened instantaneously
after detection of a fault. In AC systems with DC components, as is the case when rectifiers
are used, up to 15 s can be needed.
Note
If the 3UG4583 insulation monitoring relay is used for monitoring the winding insulation of a
motor, the function test first results in a fault message if the closed-circuit principle is
selected, since the device is not applied to the supply voltage until a measurement is
possible on the switched-off motor. Either this fault must be hidden by downstream logic, or
the open-circuit principle must be set. The output relays would only pick up if an insulation
fault or internal device faults are detected. However, the fault "Missing supply voltage" can
then no longer be detected.
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