A Striking Difference
Operational cost efficiency is best served with intrinsic reliability and maintainability. The build quality of the product and equipment should always be designed-in rather than added too as an afterthought. The system application should be considered as a whole not in isolation.
By Network Rail’s own declaration the UK rail infrastructure is damaged by lightning some 192 times each year, causing on average 361 minutes of delay per event, plus an average nearing 60 train journeys are cancelled. At a very large cost per minute, that is a lot of lost revenue and incurred penalties, and a lot of disgruntled passengers.
Railway networks are a playground for naturally occurring lightning incidents, and those which are due to human error and disturbances emanating from the system itself. The resulting increases in voltage are looking for the quickest path to earth and it does not care what is in its way. The Railway is a mass of steel connections which make excellent electrical conductors transmitting the resultant over voltage via electrical and electronic equipment.
This excellent conductor is frequently used to detect the location of trains. Superimpose the communication voltage with a lightning strike of very high voltage and the sensitive electronic signalling equipment is most likely damaged. As the signalling system will fail safe when a component is damaged or an interruption is detected, all signals in the area turn red and the trains stop.
These rapidly increasing voltages, which are commonly referred to as surges, will only last for a very short period of time - nanoseconds, microseconds to a few milliseconds – but in this time untold damage can occur to the unprotected equipment, both large and small. It is a mistake to believe that a transformer will eliminate the effects of rapid transients.
A holistic approach to surge protection can efficiently and cost effectively provide an ideal and robust solution. The system, the application and the correct selection of protection will improve reliability and reduce failures.
PD Devices worked with Network Rail to design and make a product, which was then put in to trial for two years, in differing locations of the rail network and applied to only a part of the signalling system. The outcome reported was a reduction in failures of 33%.