The Siemens SIRIUS 3UG4581-1AW30 is an insulation monitoring relay with analog setting, designed for continuous supervision of ungrounded AC systems (IT systems) up to 400 VAC. It measures insulation resistance against earth and triggers an alarm when the value drops below the set threshold (initial value 0.85, full-scale 1.1). The wide control supply range — 24 to 240 VAC/DC — means it can be wired into most control panels without a separate power supply module. The screw-type terminals accept solid 20–12 AWG or stranded 18–14 AWG (0.75–2.5 mm² with ferrule), with a tightening torque of 0.6–0.8 N·m. IP20 protection suits clean, dry cabinet environments — no washdown areas.
The measurable voltage range of 0–400 VAC at 50/60 Hz defines the system voltage it can monitor — this is for standard low-voltage IT networks up to 400 V line-to-line. The control supply voltage (24–240 VAC/DC) is separate from the monitored circuit; you can power the relay from a 24 VDC panel supply while it watches a 400 V motor feeder. Surge voltage resistance rated at 6000 V gives confidence against switching transients in industrial panels. The 100 mm depth fits standard shallow enclosures; the 22.5 mm width matches the compact SIRIUS modular profile, leaving room for adjacent contactors or relays on the same DIN rail.