The Siemens 7UG0818-1CA20 is a sophisticated digital line monitoring relay designed to ensure the reliability and safety of your three-phase electrical systems. This self-powered device provides comprehensive protection by continuously analyzing power quality and immediately detecting faults that could lead to equipment damage or costly downtime .
Key Features & Benefits
- Comprehensive Power Quality Monitoring: The relay actively monitors for a wide range of faults, including phase failure, phase sequence reversal, phase asymmetry/imbalance, under/over-voltage, and under/over-frequency .
- Versatile System Compatibility: Selectable for use in both 3-wire and 4-wire networks, making it adaptable to various installation requirements .
- Self-Powered Operation: It is a self-powered device, drawing its operating power directly from the monitored 3-phase supply (415V AC system). This simplifies wiring and eliminates the need for a separate auxiliary power source .
- Advanced Digital Configuration: Features a user-friendly interface with an integrated LCD for clear display of parameters and fault types, along with LED indicators for power and relay status. It offers flexible setting options for trip delays, hysteresis, and reset modes (Auto/Manual) .
- Dual Changeover Contacts: Equipped with 2x 1CO (Changeover) output contacts (rated at 5A), providing flexibility for integration into control and alarm circuits .
- Industrial-Grade Design: With an IP20 protection rating and a compact 35mm width, it is designed for easy DIN-rail mounting in control panels and switchgear. It complies with IEC 60947-5-1 standards for safety and performance .
Technical Specifications
| Specification | Detail |
|---|---|
| Type | Digital Line Monitoring Relay |
| Article No. | 7UG0818-1CA20 |
| Network Compatibility | 3-Phase, 3-Wire / 3-Phase, 4-Wire (Selectable) |
| Supply Voltage | Self-powered (415V AC system) |
| Operating Band (L-L) | 280 – 500V AC |
| Operating Band (L-N) | 160 – 288V AC |
| Protection Functions | Under/Overvoltage, Under/Overfrequency, Phase Asymmetry, Phase Failure, Phase Reversal |
| Output | 2x 1CO (Changeover) Contacts, 5A |
| Housing Width | 35 mm |
| Mounting | 35mm DIN Rail |
| Display | LCD for parameters & fault type; LEDs for Power (ON) and Relay status (R1/R2) |
| Standards | IEC 60947-5-1 |
| Protection Class | IP20 |
Applications
The Siemens 7UG0818-1CA20 is ideal for protecting critical equipment in various sectors, including:
- Industrial plants for motor and process protection .
- Power distribution panels to safeguard transformers and switchgear .
- Commercial buildings for HVAC systems and elevators .
- Automation systems to prevent costly process interruptions .
- Marine, offshore, and renewable energy installations



















