Railway electrification in the UK – powering the future of rail
28 June 2016
One third of the UK rail network is now electrified
If you were to step onto High Speed 2 (HS2) in the northern reaches of the UK for a trip to London, it may feel like you were stepping out into a different world. Particularly for passengers departing the serene greenery of York for London’s bustling industrialism, you would be witnessing a significant change in a relatively short amount of time.
The same can be said for the journey of railway electrification, which, in the space of 133 years, has gone from a quarter mile of track to the majority of the UK. Every journey begins with a single step and railway electrification is no different. In 1883, pioneering electrical engineer Magnus Volk developed the UK’s first electric railway. Running at only a quarter mile, Volk’s Electric Railway in Brighton left much to be desired but laid the groundwork for what has since become a multimillion-pound industry.
In fact, a third of the UK rail network is now electrified – which accounted for approximately 5,272km of UK routes in 2014-15. According to a 2010 Network Rail report on electrical losses, approximately 60 per cent of all rail journeys are powered electrically.
However, how did the UK get to this increase? While it did not take long for interest in Volk’s Line to drive a half-mile extension — it took until 1884 — it was not until the early 1900s that electrification was experimented with in some suburban areas. The positive reception to this led to the formation of the Electrification of Railways Advisory Committee (ERAC) in 1920 which, a year later, ushered in the first national standard for railway electrification: 1500 V DC.
Naturally, the fast-paced nature of railways and technology meant that this did not remain the standard for long. By 1956, 25kV AC overhead became the new standard for overhead lines and was used for the first main line railway electrification – which was London to Manchester/Liverpool in 1959-66. However, as with the previous voltage standard, little was done initially to implement this. In fact, there was little regulation to ensure that companies adhered to this at all. This resulted in frequent power failures on lines due to inadequate power and unmonitored quality.
Fortunately, the leniency of national standards disappeared with the introduction of the Railways Act 1993. This outlined the privatisation of railways, but also put tighter regulation on power quality and the voltage stability of the electrical infrastructure of railways. With this, businesses could no longer cut corners on power quality.
This drove a demand for reliable railway current transformers to cope with the high electrical expectations of railway applications. These current transformers had to be built to very particular specifications that would enable them to accurately measure electrical currents as well as function under the high currents of rail transport, while having effective housing and termination casing for safe operation.
With a reduction in the number of power line failures as a result of improved electrical infrastructure, the railway industry was presented with an opportunity to steam ahead with expansion.
Much of this expansion consisted of overhead lines in favour of third rail. Third rail systems, as the name indicates, transmit up to 1200 V of DC electricity through an elevated third rail line. While this may be more compact than overhead lines, it is unable to carry as much current as other options.
Conversely, overhead lines can operate with much higher electrical currents. With the use of consistently reliable insulators, transformers and support structures, as well as capacity to transmit up to 25 kV of AC electricity, it is no wonder that overhead lines are the most common form of railway power supply.
Powering the future of rail
In 2015, a new challenge to railway power quality presented itself. Certain railway operators began testing the European Rail Traffic Management System (ERTMS), a computer-controlled signalling system that will replace railway signals with digital displays in train cabs. In effect, the ERTMS will function similarly to a smart autopilot feature.
However, this poses the risk of electrical interference. Electronic devices, particularly those that transmit data, can become prone to generating this interference when they are in use and connected to a power source. The ERTMS, while fixed within the train cab, will feed data through the system in order to keep track of other trains operating on the railway.
This means that the ERTMS, while designed to ‘reduce the costs of maintaining the railway’, will in fact pose an electrical challenge that will require specialist infrastructure changes to safely filter.
Yet this is just the current stop on the journey of railway electrification. For the time being, the last destination remains the scheduled launch of HS2’s London to Manchester/Leeds expansion in 2033. Prior to this, there will be the large-scale electrification of railways such as the Great Western main line, highlighting an ever-growing demand for sufficient electrical infrastructure that can ease the transition to these new systems.
Luckily, this infrastructure already exists and it is now just a matter of adoption. The electromagnetic interference problems posed by the ERTMS, for example, are not dissimilar to those created by a multitude of electronic devices in other industrial environments. As such, these can be tackled with an electromagnetic compatibility (EMC) filter, which removes high-frequency electrical noise from the supply network.
Most current transformers designed for the rail industry are capable of functioning at a broad spectrum of frequencies. While this means that current infrastructure is sufficient in the short term, there is no telling how well it will operate with high-speed trains and ERTMS simultaneously. Railway providers may need to invest in filtration equipment to steer clear of the power quality problems and failures that previously plagued the industry.
With almost two decades of expansion planned, it is essential that rail companies in the UK invest in the technology to facilitate this next phase of growth and, in doing so, give passengers the very real feeling of stepping out into a different world.
Author: Steve Hughes, managing director of power quality specialists, REO UKhttp://www.engineersjournal.ie/2016/06/28/railway-electrification-uk-powering-future-rail/http://www.engineersjournal.ie/wp-content/uploads/2016/06/REO159-testing-rail-1-1024x660.jpghttp://www.engineersjournal.ie/wp-content/uploads/2016/06/REO159-testing-rail-1-300x300.jpgElecelectric vehicles,electricity,Network Rail,transport