Advanced ‘recoverable’ voltage limiting devices of the series BVL are designed to provide a reliable temporary connection between grounding of the traction infrastructure and return path for short or even long time period when impermissible dangerous touch voltage could be exceeded and thus dangerous for persons, animals and railway infrastructure.
Such a situation can be caused by failure of the electric railway system (DC or AC traction of metro, trains, trams,…) – i.e. failure of contact line etc., but also by normal operation of rolling stock – i.e. stray currents and dangerous touch voltages raised due to the train traffic.
An integrated “heavy-duty” A2 surge arrester is very effective and quick (25 nanosec.) lightning protection. With a small delay of 1.5ms (adjustable on request in factory) two electronically triggered anti-parallel thyristors react, capable to conduct high levels of stray or failure current for a long time. Our BVL-50 and BVL-100 VLDs are capable of repeatedly working with energy pulses of up to 11 MA²s and as VLD-F even up to about 110 MA²s.
High short time, as well as long time withstand currents, mean they can be used in a wide range of applications, including the most demanding in passenger stations, tunnels, close switching stations and substations, workshops, etc. The smallest BVL-25 has been designed for special application – the protection of railway signalling and measuring electric and electronic equipment which could be affected or damaged by overvoltage during rolling stock passing by. It is easy to install additionally to small technology boxes thanks to extremely small dimensions and weight.
The triggering voltage 45V and 60V for workshops and 120V for normal operation could be selected. These VLDs do not require external power supply which increases their reliability. The design in class 2.2 allows both DC and AC traction power systems to be used. Small dimensions, low weight and thermal overload sensor make installation and maintenance easier.
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