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  • Electrical safety for unearthed power supplies (IT systems)
  • Insulation monitoring equipment, insulation fault location systems
  • Power supplies for medical applications
  • Measuring and monitoring relays
  • Electrical safety for earthed power supplies (TN systems)
  • Using renewable energies efficiently: wind power, photovoltaics
  • Test systems for electrical equipment and medical technology


  • Undervoltage, overvoltage and frequency monitoring of AC/DC systems 9.6…150 V (VME421H-D-1), 70…300 V (VME421H-D-2)
  • Integrated energy storage, is supplied by the system being monitored
  • Various monitoring functions selectable U, f
  • Password protection for device setting
  • Preset function (automatic setting of basic parameters)

The voltage relays of the VME421H 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, installation-specific characteristics, such as device-specific start-up procedures, short-time voltage fluctuations, etc. can be considered. Device version VME421H takes the supply voltage from the system being monitored and utilizes an internal energy backup.


  • Undervoltage, overvoltage and frequency monitoring of AC/DC systems, 9.6…150 V (VME421H-D-1), 70…300 V (VME421H-D-2)
  • Without external supply voltage
  • Integrated energy backup
  • Different monitoring functions selectable < U, > U, < f, > f
  • Start-up delay, response delay, 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 assignment of basic parameters)
  • LEDs: Power On, Alarm 1, Alarm 2
  • Measured value memory for operating value
  • Continuous self monitoring
  • Internal test/rest 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


  • 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

Downloads for LINETRAXX® VME421H

Manuals VME421H 2.2 MB DE13.05.2019 10:31:45D00141
Manuals VME421H 2.1 MB EN13.05.2019 10:31:52D00141
Manuals VME421H 452.3 KB ES13.05.2019 10:31:54D00141
Datasheets VME421H 414.9 KB DE23.12.2021 12:52:10D00141
Datasheets VME421H 409.2 KB EN23.12.2021 12:52:18D00141
Datasheets VME421H 394.3 KB ES23.12.2021 12:53:14D00141
Datasheets VME421H 540.1 KB ZH13.05.2019 10:31:33D00141
Datasheets XM420-Schnittstellenoptionen 264.1 KB DE13.05.2019 10:31:35
Datasheets XM420 interface options 223.5 KB EN13.05.2019 10:31:36D00051

Optional accessories for LINETRAXX® VME421H

TypeArt No.
Mounting clip for screw fixing (1 piece per device)B98060008


TypeNominal system voltage Un*Response valueArt. No.**
VME421H-D-1DC 9,6…150 V / AC 9,6…150 V, 15…46 HzAC/DC 9,6…150 VB73010003
VME421H-D-2DC 70…300 V / AC 70…300 V, 15…460 HzAC/DC 70…300 VB73010004

* absolute values
**(B7… = push-wire terminal / B9… = screw-type terminal)