Voltage Limiting Devices (VLDs)

Voltage Limiting Devices help to provide a safe method of controlling and discharging fault current and are often installed on structures or extraneous conductive items.
Holding Rail Product Box


Voltage Limiting Devices are an integrally important electrical safety product required by all light rail projects. With a capacity to react to sudden spikes in electrical current, these devices are largely used to protect human life in the event of a dewirement, or fall of the overhead lines. Considering an example of that, if the overhead line falls it may come into contact with a conductive item, such as a metal hand rail, or street furniture. To avoid this conductive item becoming live and potentially harmful to people adjacent to them, or indeed directly contacting them, a voltage limiting device will quickly divert the current away.

  • Usually in rail projects voltage limiting devices are used for every tram stop, as this is certainly an area where the public could potentially have aggregated in the vicinity of the tram line. 
  • Also considered for application of a voltage limiting device is any item exceeding certain tolerance parameters, be they conductive structures, or conductive structures that fall within a defined distance from the running rails of the tram line.
  • The FM Sudafix Group has supported and assisted the research and development phase of light rail specific voltage limiting devices, and this product line has now been bought in numbers by project teams on high profile European tram projects.

Electrical safety products for railways

Rail Bonds

Rail Bonds

This product line is an essential component aspect of any railway programme as they provide electrical equipotentialisation between two conductive zones.


Surge Protection Devices are used to protect equipment from the threats of fault current, which helps keep the valuable item working and railway lines running.
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