Innovative technologies for safe handling of electrical power to achieve high availability

We offer you first-class quality and safety combined with global service and every support in resolving your monitoring problems.

  • 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


  • Pure analogue technology for safety applications
  • For nominal system voltages up to 690 V
  • Undervoltage and overvoltage monitoring for 3 AC systems

The voltage relay VMD258 monitors three-phase AC systems for undervoltage and overvoltage (window function). Neutral conductor connection is not required, therefore it is suitable for 3AC systems.

The voltage to supply the electronics is taken from the system to be monitored. The supply of the electronics, the relays and the connection for the external energy storage device are isolated from the system by means of double isolation. Special input transformers attenuate interferences from the system.

The response values for undervoltage and overvoltage as well as the response delays are continuously adjustable.


  • Undervoltage and overvoltage monitoring for 3AC systems
  • No separate supply voltage required
  • Separate alarm relays for undervoltage and overvoltage with two potential-free changeover contacts
  • Adjustable response value: 0.7…0.95 x Un/1.05…1.3 x Un
  • Nominal system voltages: 3AC 690/500/480/440/400/230/110/100 V
  • Adjustable response delay: 0…5 s
  • LEDs for operation, overvoltage, undervoltage


  • Monitoring of the power supply of machines and electrical installations
  • Monitoring of loads
  • Switching electrical systems on and off at a certain voltage level
  • Monitoring of stand-by and emergency supply systems
  • Supply voltage monitoring of portable loads

Downloads for LINETRAXX® VMD258

Manuals VMD258 406.1 KB DE13.05.2019 10:31:44D00068
Manuals VMD258 406.1 KB EN13.05.2019 10:31:44D00068
Datasheets VMD258 418.4 KB DE13.05.2019 10:31:34D00068
Datasheets VMD258 416.4 KB EN13.05.2019 10:31:36D00068
Datasheets VMD258 467.4 KB ZH13.05.2019 10:31:33D00068

Optional accessories for LINETRAXX® VMD258

Type designationArt. No.
Additional mounting clips (screw mounting)B98060008
External energy storage ES258B93010068

LINETRAXX® VMD258 Variants

TypeConnectionArt. No.
VMD258 3AC 100 V3AC, 100 VB93010060
VMD258 3AC 110 V3AC, 110 VB93010061
VMD258 3AC 230 V3AC, 230 VB93010062
VMD258 3AC 400 V3AC, 400 VB93010063
VMD258 3AC 440 V3AC, 440 VB93010064
VMD258 3AC 480 V3AC, 480 VB93010065
VMD258 3AC 500 V3AC, 500 VB93010066
VMD258 3AC 690 V3AC, 690 VB93010067