VME421H-D-2 BENDER

In order to meet the requirements of the applicable standards, customised parameter 

settings must be made on the equipment in order to adapt it to local equipment and 

operating conditions. Please heed the limits of the range of application indicated in the 

technical data.

Description:

Typical applications

• 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

Function

Once the supply voltage is applied, the start-up delay “t” begins. Measured voltage and 

frequency values changing during this time do not influence the switching state of the 

alarm relays.

The devices feature two separately adjustable measuring channels (overvoltage/undervoltage). When the measuring quantity exceeds the response value (“Alarm 1”) or falls 

below the response value (“Alarm 2”), the time of the response delays “ton1/2” begins. 

Once the response delay has elapsed, the alarm relays switch and the alarm LEDs light 

up. When the measuring value exceeds or falls below the release value (response value 

plus hysteresis) after the alarm relays have switched, the selected release delay “toff” begins. When “toff” has elapsed, the alarm relays switch back to their initial position. When 

the fault memory is activated, the alarm relays remain in alarm position until the reset 

button R is pressed. Also in the event of complete power failure of the system being 

monitored, the delay times are effective during the energy backup discharging time.

Energy backup

Also in the event of complete power failure of the system being monitored, the delay times 

are effective during the energy backup time. When the fault memory is set to continuous 

mode, the alarm parameters remain stored, even on failure of the supply voltage.

Preset function

After connecting the device for the first time, the nominal system voltage will be determined (PrE run), and the response values for overvoltage and undervoltage as well as for 

underfrequency and overfrequency will automatically be set. When no voltage is determined within a nominal system voltage range (PrE run), the response values will be set to 

the minimum or maximum voltage. In this case, the message “AL not SET” appears on the 

display. As long as no button is pressed, a nominal system voltage is being searched cyclically 

(PrE run). If a button is pressed, the search will be interrupted and the message “AL not SET” 

disappears. In this case, the appropriate response values have to be set in the menu. 

When activating the frequency monitoring function, the preset frequency will automatically 

be stored.

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