The UG140P is an earth fault relay (UG-ISOMETER®) from Bender, designed for monitoring the insulation resistance of unearthed DC systems (IT systems) to earth. The device is preferably used in simple control voltage systems of limited extent, which contain no control devices and whose system leakage capacitances are no greater than 1 µF.
The device uses a passive measuring principle with a bridge circuit for automatic fault indication. Due to this passive measuring principle, only unbalanced insulation faults (insulation degradation on the positive or negative pole to earth individually) can be detected. Symmetrical insulation faults (simultaneous equal degradation of insulation resistance on both the positive and negative poles to earth) are not recorded.
The device has order number B916382, rated system voltage DC 24 V, and response value 25 kΩ. The UG-ISOMETER® does not fall under the definition of insulation monitoring devices according to IEC 61557‑8.
Technical Specifications
Insulation coordination (according to IEC 60664‑1):
· Rated insulation voltage: AC 250 V
· Rated impulse withstand voltage/pollution degree: 4 kV/3
Voltage ranges:
· Rated system voltage Uₙ: DC 24 V
· Operating range: 0.8 … 1.1 × Uₙ
· Supply voltage Uₛ = Uₙ (self‑powered)
· Max. power consumption: 2.7 VA
Response values:
· Response value Rₐₙ: 25 kΩ (DC 24 V version)
· Max. permissible system leakage capacitance Cₑ: ≤ 1 µF
Measuring circuit:
· Measuring current Iₘ: max. 0.3 mA
· Internal DC resistance Rᵢ: 40 kΩ
Contact circuit:
· Switching elements: 2 voltage‑free SPDT changeover contacts
· Rated contact voltage: AC 250 V / DC 300 V
· Rated current: 5 A
· Breaking capacity: 2 A at AC 230 V / cos phi = 0.4
· Electrical endurance: 12000 cycles
Environment and mounting:
· Operating temperature: ‑10 °C … +50 °C
· Storage temperature: ‑20 °C … +70 °C
· Connection: modular terminals
· Mounting: DIN rail or screw fixing (mounting plate order no. 990 056)
· Degree of protection: internal components IP30, terminals IP20
· Weight: max. 200 g
Key Features
· DC system insulation monitoring: Continuously monitors the insulation resistance of DC IT systems to earth
· Fixed response value alarm: Preset response value of 25 kΩ for DC 24 V systems
· Dual alarm outputs: Two voltage‑free SPDT changeover contacts
· Fault memory function: Fault alarm latching can be enabled via terminals or external reset button
· Self‑powered design: Powered directly from the monitored system, no external supply required
· Built‑in indicators: Power ON LED and alarm LED
· Built‑in test/reset buttons: Integrated test and reset buttons
· 45 mm enclosure: Compact design
Typical Applications
· DC control circuit monitoring: For DC control voltage systems in industrial plants, power stations and substations
· Simple battery systems: Monitoring insulation of battery banks
· Small DC control systems: For small DC unearthed systems
· DC lighting circuits: Monitoring insulation of DC lighting systems
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