VME420-D-2, voltage relay

Voltage relays

LINETRAXX ® VME420Product description The VME420 series of voltage relays monitor frequency, subvoltage, overvoltage and the voltage between two threshold values in AC and DC systems. The voltages are measured as effective values. The current measured value is permanently displayed on the LC display. The measured value leading to the switching of the alarm relay is stored. Due to adjustable delay times, plant-specific properties can be taken into account: The VME420 version requires an external supply voltage. Examples of applications • Voltage and frequency monitoring of single-phase machines and systems • Ground-end monitoring via voltage converters in medium-voltage networks • Monitoring of battery systems • Switching on and off systems from a certain voltage function description After the supply voltage is set, the start-up delay "t" starts. During this time, changes in the measured voltage and frequency do not affect the switching state of the alarm relay. The devices have two separately adjustable measuring channels (over- / undervoltage). If the measurement size exceeds the response value ("Alarm 1") or below ("Alarm 2"), the set response delays start "ton1 / 2." After the response delay is over, the alarm relays and the alarm LEDs turn on. The set drop time "toff" starts below or above the measurement size after switching the alarm relay. After the end of "toff" the alarm relays turn back to the initial position. If the error storage is activated, the alarm relays remain in alarm position until the reset key is activated. When the error storage behaviour "con" is selected, the alarm LEDs and relays are set back to the state before voltage failure after voltage recovery. Preset function After the first switch on of the device, the power supply voltage is determined (pre run) and the response values for over- and undervoltage and sub- and overfrequency are automatically set. If no voltage is determined within a power supply voltage range (PrE run), the response values are set to the minimum or maximum value. For information, the display "AL not SET" is then displayed. As long as no key is operated, a net voltage is cyclic (PrE run). If a key is activated, the search will be stopped, the message "AL not SET" will no longer appear. The response values must then be set to the desired values in the menu. When the frequency monitoring is activated, the automatic default of the frequency is also taken over.