The voltage relays of the VME420 series are designed to monitor the frequency, undervoltage, overvoltage and the voltage between two threshold values (window discriminator function) in AC and DC systems. The voltages are measured as r.m.s. values. The currently measured value is continuously shown on the LC display. The measured value leading to the activation of the alarm relays will be stored. Due to adjustable response times, installationspecific characteristics, such as device-specific start-up procedures, short-time voltage fluctuations, etc. can be considered . Device version VME420 requires an external supply voltage.
 

• Monitoring AC/DC systems for undervoltage, overvoltage and frequency in the voltage range of 0…300 V
• Various monitoring functions selectable
• < U, > U, < f, > f
• Start-up delay, response delay and delay on release
• Adjustable switching hysteresis
• r.m.s. value measurement (AC+DC)
• Digital measured value display via multi-functional LC display
• Preset function (automatic setting of basic parameters)
• LEDs: Power On, Alarm 1, Alarm 2
• Measured value memory for operating value
• Continuous self monitoring

• Single-phase voltage and frequency monitoring of machines and electrical installations
• Earth fault monitoring in medium-voltage systems via voltage transformers
• Monitoring of battery systems
• Switching on and switching off at a certain voltage level