Voltage limiting devices of the series SCG are designed to quickly detect and limit overvoltage caused by the failure of the electric railway system (metro, trains, trams), lightning strike or another origin of dangerous excessive touch voltage on exposed conductive parts of railway infrastructure (DC or AC traction).

The principle of protecting people who may come into contact with these parts is the SCG ensures the temporary or permanent connection of the conductive parts to the return path for as long as dangerous excessive touch voltage can occur. The short-circuit current, which goes through the open SCG surge protector when the overhead contact line falls, is evaluated by a sensor in the relevant traction substation and the affected part of the traction line is automatically disconnected by an automatic substation disconnector.

VLD’s class 1 is guaranteed in accordance with EN 50526-2 ed.2 by a patented internal short-circuit device which automatically provide very low impedance (milliohms) by-pass of protective element during high passing failure current. The used protective elements of this VLD also provide effective pulse overvoltage protection of persons and railway devices even caused by lightning strikes.

The triggering voltage 75V, 250V or 480V could be selected for various protection requirements. In addition to excellent electrical parameters (up to 100kA current impulse), these voltage limiting devices are characterized by low weight and small dimensions for easy handling and installation.

A typical application of these affordable voltage limiting devices could be ‘rail grounding’ of catenary masts (or their interconnected groups), conductive parts of railway stations and switching stations to the return path etc according to the EN 50526-3 standard.

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