The DOLD UG 9831.12 Series DC Voltage Monitoring Relay (German: DC-Spannungsrelais / English: DC Voltage Relay) is a high-grade electrical measurement and protection instrument belonging to the prestigious VARIMETER family, researched and engineered by E. DOLD & SÖHNE GmbH & Co. KG in Germany. In modern power infrastructure, direct current (DC) power architectures are expanding rapidly across utility-scale solar photovoltaic fields, commercial battery energy storage systems (BESS), electric vehicle (EV) DC high-power charging facilities, and electrified railway networks. In these demanding environments, unmonitored DC voltage fluctuations—whether excessive overvoltage caused by sudden load rejection and switching surges, or severe undervoltage triggered by deep battery cell discharge—pose critical hazards that can rupture DC-link capacitor banks, destroy high-power IGBT semiconductors, damage battery storage banks, or cause catastrophic outages in critical backup power systems.

The DOLD UG 9831 series is engineered specifically to provide dependable, continuous voltage surveillance across these severe DC environments, featuring an ultra-wide measuring span from DC 20V up to 1000V. The ability to directly measure and withstand voltages up to DC 1000V without requiring external potential dividers or auxiliary scaling transducers simplifies control cabinet architecture, reduces parasitic heat dissipation, and elevates overall operational reliability. Utilizing precision solid-state electronics paired with calibrated front-panel rotary setting switches, the device allows commissioning engineers to configure exact trigger setpoints with exceptional repeat accuracy. Furthermore, a sealable transparent front cover protects the adjustment dials from accidental displacement or unauthorized tampering on the factory floor.

This comprehensive entry consolidates two specialized functional models within the DOLD UG 9831 family:
1. DOLD UG9831.12 DC20-1000V UH=DC24V: Standard model configured for dedicated Overvoltage or Undervoltage supervision. Operating modes are selectable via integrated slide switches, while an adjustable operate delay filters out transient voltage spikes and switching dips to prevent nuisance tripping.
2. DOLD UG9831.12/100 DC20-1000V UH=DC24V: Advanced model featuring integrated Window Monitoring (Fensterüberwachung). This variant allows simultaneous calibration of both an upper threshold (Umax) and a lower threshold (Umin). As long as the monitored DC potential remains strictly within this defined safe operational window (Umin < U < Umax), the relay maintains a healthy state; any deviation above Umax or below Umin immediately triggers the safety output contacts. This represents the optimal protection solution for Lithium-ion battery operating envelopes and variable speed drive DC-bus voltage links.

Featuring the ".12" contact architecture with 2 independent changeover contacts (2 C/O - 2 x 1 Wechsler) with high industrial breaking capacity, the device easily handles simultaneous circuit breaker tripping and PLC alarm telemetry. Housed within a space-saving UG modular enclosure with a slim width of only 22.5 mm, it snaps onto standard 35mm DIN-rails. Multi-status front diagnostic LEDs provide instantaneous visual feedback regarding auxiliary power status and active relay contact states. Fully compliant with international standard IEC/EN 60255-1, the DOLD UG 9831 is an indispensable protective component for renewable energy substations, data centers, traction networks, and automated industrial processing plants worldwide.

• Manufacturer: DOLD (E. DOLD & SÖHNE GmbH & Co. KG)
• Country of Origin: Germany
• Product Series: VARIMETER UG 9831
• Technical Category: DC Voltage Monitoring Relay (DC-Spannungsrelais)
• Integrated Models in this Entry:
  - DOLD UG9831.12 DC20-1000V UH=DC24V (Overvoltage / Undervoltage monitoring model)
  - DOLD UG9831.12/100 DC20-1000V UH=DC24V (Window monitoring model)
• Rated Measuring Voltage Range: DC 20 ... 1000 V (Direct high-voltage DC measurement)
• Auxiliary Supply Voltage (UH): DC 24 V
• Voltage Tolerance Range: 0.85 ... 1.15 UH
• Monitoring Functions:
  - Standard UG9831.12: Overvoltage or Undervoltage monitoring (selectable)
  - Variant /100: Voltage Window Monitoring (simultaneous upper Umax and lower Umin threshold supervision)
• Setting Mechanism: High-precision front rotary switches with sealable transparent anti-tamper cover
• Operate Delay: Adjustable response delay to filter out transient electrical disturbances
• Output Contact Arrangement: 2 Independent changeover contacts (2 C/O - 2 x 1 Wechsler)
• Switching Capacity: AC-15: 3A / AC 230V; DC-13: 1A / DC 24V (compliant with IEC/EN 60947-5-1)
• Continuous Thermal Current (Ith): Max. 5A
• Visual Status Diagnostics: Front LED indicators for auxiliary power (ON) and individual relay contact states
• Module Dimensions (W x H x D): 22.5 x 100 x 121 mm (Ultra-slim UG enclosure)
• Mounting Profile: Quick snap-on mounting on standard 35 mm DIN-rail (IEC/EN 60715)
• Terminal Architecture: Vibration-resistant box clamp screw terminals designed for secure industrial cabling
• Protection Rating: Housing IP40, Terminals IP20 (according to IEC/EN 60529)
• Ambient Operating Temperature: -20°C to +60°C
• Compliant Safety Standards: IEC/EN 60255-1, IEC/EN 60947-5-1, CE
• Common Industrial Deployments: Solar PV combiner boxes, BESS container storage, EV DC fast chargers, inverter DC-bus links, and electrified railway substations