How is the railway being electrified?

Rail electrification is the process of enabling electric trains to run on railways tracks. This allows rail network providers to phase out engines powered by diesel or coal. This gives the railway the potential to be greener: 

  • Removes older, inefficient diesel powered locomotives from the network, reducing emissions,
  • The power for the whole network is generated in centralised locations and in a more efficient manner,
  • If the electricity can be generated from renewable sources, the entire railway network can become more environmentally friendly. 

The process of electrification has been underway in the UK for a number of years, but it requires labour-intensive trackside works that take significant periods of time. Elements of the network, such as the London Underground, have been electrified since 1890, though this was in part due to the fumes from steam trains causing issues in the underground. The modern push for electrification is centred more on the need to reduce operating costs and the carbon footprint of the rail network by switching to more renewable and efficient energy sources. For Network Rail, the owners of the UK track network, their preferred method is to install overhead line equipment (OHL), although other methods include the third rail, which is – as the name implies – a third rail next to the track that is electrified, with trains drawing the current through a shoe fitted to the train.  Other less conventional methods include linear motors and fourth rail systems.

In every case, these works cannot be undertaken whilst the tracks are active so track possessions must be agreed to close the track to both passenger and freight movements for an agreed period whilst contractors do the work. Possessions can be longer (and therefore more costly) where works include civil engineering activities such as raising bridges - in many cases bridges over rail lines were not built with overhead line electrification in mind and so do not offer enough clearance.

There is a variety of different methods of electrifying rail networks. The most popular method worldwide is  overhead line systems, where overhead cables carry the current, and trains are fitted with a device to draw current from the line to power the locomotive. The term overhead line covers a range of equipment - from the power line itself (All Aluminium Conductors (AAC) in the UK often referred to as Hornet and Cockroach) to the catenary wire and flexible conductors that combine to connect to the pantograph on top of the train itself.

While some repair and maintenance are expected over time, its essential that these cables are able to withstand the conditions they are installed in as otherwise a busy network will quickly grind to a halt!

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