The VME420 series voltage relays are designed to monitor the frequency, undervoltage, overvoltage and the voltage between two threshold values 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 required to trigger the alarm relay is stored. Due to adjustable response times, installation-specific characteristics, such as device-specific start-up procedures, short-time voltage fluctuations, etc. can be considered. The relays require an external supply voltage.

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

• 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
• Internal test/reset button
• Two separate alarm relays
(one changeover contact each)
• N/C or N/O operation and fault memory behaviour selectable
• Password protection for device setting
• Sealable transparent cover
• Two-module enclosure (36 mm)
• Push-wire terminal
(two terminals per connection)
• RoHS compliant