Why is there lightning and sparks on the overhead lines of the railways in winter - and is it dangerous?
Created: 12/15/2022, 3:00 p.m
By: Franziska Kaindl
Freezing temperatures often ensure that frost forms on the overhead lines for trains.
When trains pass, there is often a shower of sparks.
As soon as the outside temperature drops to minus degrees, rail passengers often witness a striking phenomenon: When trains arrive, lightning and sparks form on the overhead line - usually accompanied by an audible crackling.
What may seem intimidating at first is not dangerous, as operators reveal.
Sparks and lightning from icy overhead lines are harmless
"If small frost crystals settle on the overhead lines in cold weather, the catenary ices up and the flow of electricity is prevented," wrote the
Dresden public transport company
on Facebook a few years ago.
However, the 600 volt voltage at the pantograph of a tram would easily iron the line free of ice again.
The ice resistance is bridged with an arc - the lightning would literally "burn away" the ice.
In freezing temperatures, the overhead lines of trains can freeze over.
© Arnulf Hettrich/Imago
The ice flashes are not dangerous, however, as both the
Dresden transport company
and the spokesman for the
Üstra Hannoversche Verkehrsbetriebe
report, according to the online portal
Reisereporter
.
"Due to the intensity of the light, however, I recommend not looking directly into the arc," says Jürg Briner from the
Swiss Federal Railways (SBB)
in a report by
Swiss Radio and Television (SRF).
In order to anticipate the wintry weather, the Dresden public transport company also uses "Schmiertatras" according to the Facebook post.
"These are equipped with felt rollers on the bracket, which grease the overhead line with glycerin," it says.
The lubricating film prevents the lines from icing up.
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Overhead lines for trains: Freezing rain can cause major problems
However, it can also happen - albeit rather rarely - that a real ice mantle forms around the overhead line.
It ensures that the electric locomotive loses contact with the pantograph.
The phenomenon usually occurs when freezing rain occurs overnight at low temperatures.
Last year, for example, the trams between Leopoldshafen and Hochstetten near Karlsruhe were paralyzed, as reported by the
Badische Neue Nachrichten
.
Good to know
The power supply in the train is not affected by an icy catenary.
Train passengers don't have to worry about the air conditioning or lighting failing.
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In such a case, the electric locomotive could try to slowly drive down the affected route in order to warm up the line, as reported by the news portal
Nordbayern
.
Otherwise, a tower railcar can also be used to free the catenary from the layer of ice.
The wagons are also used to inspect damage to the overhead line more closely.