Editing Overhead line (section)

==Problems with overhead equipment==
Overhead lines may be adversely affected by strong winds causing wires to swing.<ref>{{cite web|url=http://ing.dk/artikel/kamerasystem-skal-advare-lokofoerere-mod-svingende-koereledninger-paa-storebaelt-163994|title=Kamerasystem skal advare lokoførere mod svingende køreledninger på Storebælt|date=5 November 2013|access-date=25 June 2016|language=da}}</ref> Power storms can knock the power out with [[lightning]] strikes on systems<ref>{{cite web|url=http://www.ocs4rail.com/author/admin/|title=Garry Keenor – Overhead Line Electrification for Railways|language=en-US|access-date=2019-02-05}}</ref> with overhead wires, stopping trains following a [[Voltage spike|power surge]].

During cold or frosty weather, ice may coat overhead lines. This can result in poor electrical contact between the collector and the overhead line, resulting in electrical arcing and power surges.<ref>{{cite news |first= Matt |last= Stewart |date= 21 May 2012 |title= Matangi trains 'more susceptible' to frost |url= http://www.stuff.co.nz/dominion-post/news/6956618/Matangi-trains-more-susceptible-to-frost |newspaper= [[The Dominion Post (Wellington)|The Dominion Post]] |location= Wellington |access-date= 2 September 2015}}</ref> Ice coatings also add extra weight, as well as increase their surface area exposed to wind, consequently increasing the load on the wires and their supports.

Lines may sag during hot weather and if a pantograph gets entangled, this can result in a dewirement. Similarly, in very cold weather they may contract and snap.

The installation of overhead lines may require reconstruction of bridges to provide safe electrical clearance.<ref>{{Cite book|last=Keenor|first=Garry|date=2014 |doi=10.1049/ic.2014.0056|isbn=9781849199803|chapter=Series 1: A User's Perspective &#91;railway electrification&#93;|title=Railway Electrification|pages=6 (7 .)}}</ref>

Overhead lines, like most electrified systems, require a greater [[capital expenditure]] when building the system than an equivalent non-electric system. While a unelectrified railway line requires only the grade, ballast, ties and rails, an overhead system also requires a complex system of support structures, lines, insulators, power-control systems and power lines, all of which require maintenance. This makes non-electrical systems more attractive in the short term, although electrical systems can pay for themselves eventually. Also, the added construction and maintenance cost-per-mile makes overhead systems less attractive on already existing long-distance railways, such as those found in North America, where the distances between cities are typically far greater than in Europe. Such long lines require enormous investment in overhead line equipment, which private rail companies are unlikely to be interested in, and major difficulties confront energizing long portions of overhead wire on a permanent basis, especially in areas where energy demand already outstrips supply.

Many people consider overhead lines to be "[[visual pollution]]", due to the many support structures and complicated system of wires and cables that fill the air. Such considerations have driven the move towards replacing overhead power and communications lines with buried cables where possible. The issue came to a head in the UK with the [[Great Western Main Line]] electrification scheme, especially through the [[Goring Gap]]. A protest group with their own website has been formed.<ref>{{cite web|url=http://www.savegoringgap.org.uk/|title=Save the Goring Gap|website=Save the Goring Gap|language=en|access-date=2019-02-05}}</ref>

The valuable copper conductor can also be subject to theft, as for example the [[Pakistan Railways#Electrification|Lahore-Khanewal line in Pakistan]] and the [[National Railways of Zimbabwe#Operations|Gweru-Harare section of line in Zimbabwe]].