Over-voltage monitoring relay LINETRAXX® VMD421H series
frequencyphase sequencephase loss

over-voltage monitoring relay
over-voltage monitoring relay
over-voltage monitoring relay
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Measured/monitored value
over-voltage, frequency, phase sequence, phase loss, phase unbalance
Contact configuration
Other characteristics
adjustable, multifunction, DIN rail


The multi-functional VMD421 series voltage relay is designed to monitor the frequency, undervoltage and overvoltage and the voltage between two threshold values (window discriminator function) in 3(N)AC 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, installationspecific characteristics, such as device-specific start-up procedures, short-time voltage fluctuations, etc. can be considered. The devices are supplied by the system being monitored and utilise an internal energy backup.


*Prices are pre-tax. They exclude delivery charges and customs duties and do not include additional charges for installation or activation options. Prices are indicative only and may vary by country, with changes to the cost of raw materials and exchange rates.