Editing Overhead line (section)

== Multiple overhead lines ==
[[File:Overhead conductor rails.jpg|thumb|Two [[#Overhead conductor rails|overhead conductor rails]] for the same track. Left, 1,200&nbsp;V DC for the [[Sihltal Zürich Uetliberg Bahn|Uetliberg railway]] (the pantograph is mounted asymmetrically to collect current from this rail); right, 15&nbsp;kV AC for the Sihltal railway]]

Some railways used two or three overhead lines, usually to carry [[three-phase]] current. This is used only on the [[Gornergrat Railway]] and [[Jungfrau Railway]] in Switzerland, the [[Petit train de la Rhune]] in France, and the [[Corcovado Rack Railway]] in Brazil. Until 1976, it was widely used in Italy. On these railways, the two conductors are used for two different phases of the three-phase AC, while the rail was used for the third phase. The neutral was not used.

Some three-phase AC railways used three overhead wires. These were an experimental railway line of Siemens in Berlin-Lichtenberg in 1898 (length {{Convert|1.8|km}}), the military railway between Marienfelde and Zossen between 1901 and 1904 (length {{Convert|23.4|km}}) and an {{Convert|800|m|adj=on}}-long section of a coal railway near Cologne between 1940 and 1949.

On DC systems, bipolar overhead lines were sometimes used to avoid [[galvanic corrosion]] of metallic parts near the railway, such as on the [[Chemin de fer de la Mure]].

All systems with multiple overhead lines have a high risk of short circuits at switches and therefore tend to be impractical in use, especially when high voltages are used or when trains run through the points at high speed.

The [[Sihltal Zürich Uetliberg Bahn]] had two lines with different electrification. To be able to use different electric systems on shared tracks, the [[Sihltal railway line|Sihltal line]] had its overhead wire right above the train, whilst the [[Uetliberg railway line|Uetliberg line]] had its overhead wire off to one side. This configuration was used up until summer 2022, since then the [[Uetliberg railway line|Uetliberg line]] has been switched to the standard 15kV 16.7&nbsp;Hz configuration.<ref>{{Cite web |last=Redaktion |date=2022-09-05 |title=Neue Uetlibergbahn S10 planmässig in Betrieb genommen [aktualisiert] |url=https://www.bahnonline.ch/23016/neue-uetlibergbahn-s10-planmaessig-in-betrieb-genommen/ |access-date=2023-06-03 |website=Bahnonline.ch |language=de-DE}}</ref>