Under-voltage monitoring relay LINETRAXX® VMD423/VMD423H

over-voltagefrequencyphase sequence

The LINETRAXX VMD423 and VMD423H voltage relay models are designed for AC systems. Frequency and voltage are monitored in accordance with DIN-V-VDE-V 0126-1-1 for the purpose of feeding power into a low voltage public grid from private generation systems greater than 30kW. Examples include wind power generators, photovoltaic systems, CHPs, etc. The output frequencies and voltages are measured via 100V transmitters at the feeding point of a medium voltage grid. When the limit values are attained, an alarm relay is triggered within ≤80ms. These relay models can be adapted to the requirements of individual electricity supply companies. Overvoltage is monitored by average determination of the previous ten-minute measuring intervals. Additional features include rms value measurement for AC+DC, start-up delay, delay on release, adjustable switching hysteresis, etc.