4-wire AC system
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Application examples
The gure below shows monitoring for ground fault/insulation fault in the case of an
ungrounded 2‑wire IT AC system. The voltage source is the secondary side of an isolating
transformer that galvanically isolates the system and the downstream circuit.
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① Loads
Figure 9-2 Monitoring for ground fault/insulation fault in the case of an ungrounded 2-wire IT AC system
Note
The maximum cable length of the control cables is 50 m or 100 pF/m.
The gure below shows monitoring for ground fault/insulation fault in the case of an
ungrounded 4‑wire IT AC system. The voltage source is the secondary side of an isolating
transformer that galvanically isolates the system and the downstream circuit.
3UG458. insulation monitoring relay.
9.3 3UG4581 insulation monitoring relay
SIRIUS 3UG4 / 3RR2 monitoring relay
166 Equipment Manual, 07/2021, NEB927043002000/RS-AD/005
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