3Ug458. Insulation Monitoring Relay - Siemens SIRIUS 3UG4 Equipment Manual

3UG458. insulation monitoring relay.

Overview
The 3UG458. insulation monitoring relays are used for monitoring the insulation resistance (in
accordance with IEC 61557‑8) between ungrounded single-phase or three-phase AC systems
and a protective conductor.
The family comprises the following devices:
• Insulation monitoring relays for ungrounded AC systems with a rated system voltage of up to
U
• Insulation monitoring relays for ungrounded AC systems, DC systems, and mixed AC/DC
systems with a rated system voltage of up to U
• Insulation monitoring relays for ungrounded AC systems, DC systems, and mixed AC/DC
systems with a rated system voltage of up to U
The measuring range can be extended up to U
upstream module.
Ungrounded, insulated systems (IT networks) are always used when high requirements are
placed on the reliability of the power supply, e.g. emergency lighting. IT systems are supplied via
an isolation transformer or voltage sources such as batteries or a generator. An insulation fault
that occurs between an external conductor and ground represents a grounding of this
conductor. This does not result in the closing of a circuit and operation can continue without
hazard (single fault security). Before a second insulation fault occurs, the first fault must be
corrected (e.g. in accordance with DIN VDE 0100‑410). Insulation monitoring relays are used to
implement this requirement. The insulation monitoring relays measure the resistance of the
external conductor and the neutral conductor against ground, and immediately report a fault if
the set insulation resistance is undershot. This procedure enables controlled shutdown, or
correction of the fault without interrupting the power supply.
The insulation monitoring relays monitor the following fault types, depending on the version:
• Open circuit
• Incorrect settings
• Ungrounded, strictly AC systems for insulation faults
• Ungrounded, strictly DC systems for insulation faults
• Ungrounded, mixed DC systems and AC systems for insulation faults (e.g. AC systems with
rectifiers or switched-mode power supplies)
Note
The use of two 3UG458 devices in a galvanically connected area (monitored area) is not
permissible.
SIRIUS 3UG4 / 3RR2 monitoring relay
Equipment Manual, 07/2021, NEB927043002000/RS-AD/005
= 400 V AC.
n
= 250 V AC and U = 300 V DC.
n n
= 400 V AC and U = 600 V DC.
n n
= 690 V AC and U = 1000 V DC by using an
n n
9
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