Power station operators demand safety analogue technology

The difference between a permanent random fault and a dynamic random fault is driving a continuing demand from power station operators and other industry sectors for vital monitoring of three phase AC systems up to 690 V in pure analogue technology.

New LINETRAXX® VMD258 voltage relays from Bender UK, which replace SUR35X series devices, monitor these AC systems for undervoltage and overvoltage (window function).

It is a vital aid to safety and power system resilience that can be employed anywhere there is equipment that has critical need for correct voltage and current, and is also used in the water, gas, electrical distribution, renewables and portable generator sectors.

Permanent random faults occur predominantly in analogue technology and remain present until they are rectified, for example through the replacement of a faulty component.  Dynamic faults on the other hand occur only under certain conditions – perhaps due to a software bug or a faulty memory cell – and are difficult to find.  Despite comprehensive tests, possible malfunctions and faults due to software cannot be excluded.

To overcome this digital threat, power station operators demand vital undervoltage and overvoltage monitoring solutions designed using pure analogue technology.  Devices for monitoring three phase AC systems designed in pure analogue technology – without microcontroller – are also required by risk analysis for safety critical areas.

Applications for the LINETRAXX® VMD258 include monitoring of the power supply to machines and electrical installations, monitoring of loads, switching electrical systems on and off at a certain voltage levels, monitoring of stand-by and emergency supply systems, and supply voltage monitoring of portable loads.

Power for VMD258 is supplied by the system to be monitored.  An additional optional energy storage device ES258 provides a bridging time of at least 5 seconds in the event of a power failure.  The supply to 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 reduce interference from the system, and response values for undervoltage and overvoltage as well as the response delays are continuously adjustable.

Bender LINETRAXX® VMD258 voltage relays do not need a neutral conductor star point connection and are therefore universally suitable for 3 AC systems up to 690 V.

Features of LINETRAXX® VMD258

  • 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



Visit the website: www.bender-uk.com

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