Rail electrification in the UK: going live?

Atkins | 04 Jun 2014 | Comments

Electrification is at the heart of a multi-billion pound programme to revitalise Britain’s rail network.

Demand for rail travel in Great Britain is soaring. In 2013, passengers made a record 1.5 billion journeys – twice the 1995 figure – and demand is expected to double again over the next 30 years. There are now more people using the railways than at any time since the 1920s and more capacity is needed. New lines, such as HS2 and Crossrail, are part of the solution, but squeezing more out of existing routes and boosting their green credentials are equally important.

Electrification holds the key.

“Electrification projects are really change projects,” says Bob Ducksbury, Atkins’ director of electrification. “When you electrify a railway, you completely change the service – trains travel faster, carry more passengers and accelerate and brake quicker, so journey times are reduced. That radically changes the way the railway is used by passengers and freight operators.”

The UK’s current electrification programme is the biggest in history. Over the next seven years, high-voltage overhead wiring will be extended across more than 2,000 miles of the existing network – a £2bn infrastructure upgrade that will see ageing diesels replaced with fast, green, electric trains capable of using low and zero-carbon electricity, including renewables and nuclear energy.

Few thought it would ever happen. Official enthusiasm for electrification waned throughout the early 2000s; by 2007, it had all but hit the buffers. Atkins’ report – Study on further electrification of Britain’s railway network – helped to change all that.

“It was a catalyst for converting direction,” recalls Ducksbury. “From 2010 onwards, momentum went from nothing to full bore.”

The lines being electrified include some of Britain’s busiest. Atkins is the lead design organisation for the electrification of Brunel’s iconic Great Western main line (GWML) linking London and Cardiff. It is also providing engineering design services in the London North Western (South), East Midlands and Scotland regions of the National Electrification Programme Framework. The strategic Midland main line to Sheffield and key routes around Birmingham are also being delivered under the framework.

Smarter tools

Railway electrification presents a number of tough engineering challenges. Schemes must be energy-efficient and compatible with new trains being procured under the Intercity Express Programme as well as existing rolling stock. In addition, electrification must comply with a raft of rigorous European standards governing everything from safety to on-train energy metering.

Engineers also have to make sure new high-voltage traction supplies won’t interfere with critical systems such as signalling and communications. Then there’s the need to ensure the installation, testing, commissioning and entry into service of the electrification infrastructure and electric trains are all delivered with minimum disruption. Upgrades need to fit within strict operational schedules.

The first steps include calculating how much electrical energy will be required, identifying where to tap into the National Grid and working out the best locations for transformers – vital if energy losses are to be minimised. Engineers also need to understand how different elements of the overall system – such as timetabling, power supplies and signalling – interact with each other.

To help deliver these insights, Atkins worked in partnership with the University of Birmingham to create the Multi Train Simulator (MTS) – an innovative infrastructure modelling tool for electrification, developed with support from the government-backed Knowledge Transfer Partnership.

MTS allows electrical engineers to delve deep into the physics of electrification to optimise the efficiency and safety of the power system. But it’s also a business tool and allows both train and infrastructure operators to explore scenarios: what happens if you increase the speed and weight of trains? Add a new station? Alter the signalling?

The ability to answer questions like these is important because the power requirements of a railway are enormous. A single freight train, for example, pulls up to 5MW, enough to light up a small town. Even subtle changes, such as altering the position of a signal, can affect the size of the load hitting the grid. MTS not only analyses the impacts of changes, it also helps operators to optimise energy consumption – a key element of carbon critical design.

“MTS brings together the best bits that exist in the marketplace and adds our own ideas,” says Ducksbury. “It’s now our standard tool.”

Innovation overhead

Atkins’ role includes the engineering design of the overhead line equipment (OLE) – the all-important wires, insulators and masts that deliver 25,000 volts AC to trains – a system known in the industry as “knitting”.

Getting power from the trackside to a speeding train is a complex business. The grey steel masts that flash past the train window might all look the same, but each has a different design story to tell. On the GWML project alone, there will be around 20,000 of them spread across a site that is, in effect, nearly 300 miles long.

Above ground, obstacles such as junctions, bridges and level crossings influence where masts can be positioned. Tunnels, viaducts, stations and signalling, meanwhile, present additional practical and aesthetic challenges that must be worked around with care and precision.

Extreme weather must also be taken into account. Variables such as wind loading and temperature effects are carefully evaluated because these influence both the design of the supports and the spacing between them.

Below ground, engineers need to take account of soil types and underlying geology because these determine the depth and type of foundations for support masts. And buried services – gas, water, signalling cables, drainage and electricity – must all be pinpointed before piles can be driven or foundations excavated safely.

Getting all of this right means managing data on a vast scale – everything from topographical surveys to track layouts and signalling plans.

To make sense of all this complexity, Atkins is developing a new modelling system that centralises all the data and provides a suite of design tools that transforms the way OLE systems are designed and built. The solution, known as TADPOLE, is based on experience built up over the last 15 years.

“TADPOLE automates the design process and takes care of the mundane and repetitive elements, freeing engineers to focus their expertise on value-added tasks,” says Ducksbury. “Because TADPOLE is automated and process-driven, it means the error rate drops significantly. Ultimately, we’ll get it to zero.”

As well as increasing the productivity of engineering design teams, TADPOLE is designed to produce results that everybody can use, at every stage of the project lifecycle – from planning and installation using modern high-output plant, to long-term maintenance of the completed infrastructure. It also helps engineers to amend designs easily if anything changes.

“The outputs can be drawings, such as plans and sections, showing the depth of foundations, the type of structure and the components you need,” explains Ducksbury. “But if a contractor prefers to work from tables or schedules, TADPOLE can provide that as well. The tools have been designed to be BIM [building information modelling] compliant and the intelligence of the design is contained in the data file.”

Digitising the design process opens up new possibilities, including easier collaboration between designers and contractors. To accelerate this process, common ground rules are needed. Working with industry partners, Atkins recently bid for and won funding from the government-backed Technology Strategy Board to standardise input and output data standards for the electrification design process.

Arching over all of these developments is Atkins’ commitment to safety. Every project is governed by “safe by design” principles that help engineers identify and reduce risks, from deployment and maintenance right through to decommissioning.

“Safety starts at the drawing board,” says Ducksbury. “Making the right decisions at the design stage significantly improves the whole-life safety performance of the solutions we deliver.”

The way ahead

Around three-quarters of Britain’s rail traffic will be powered by electricity by the time the current phase of the electrification programme is complete. But the physical proportion of the network that is electrified will still only be 55 per cent, well behind some of the UK’s European counterparts.

Where next for electrification? Infill projects – AC electrification of the missing links – will help to meet the government’s strategic objective of increasing electric freight and accelerating travel times between cities: many journeys continue to depend on diesel traction simply because relatively short stretches of cross-country routes are either not electrified or are electrified to the legacy DC standard.

This raises the wider question of DC to AC conversion. Much of the electrified network in southern England uses the “third-rail” DC power system. Conversion to overhead AC would improve energy efficiency and make it easier to operate the longer, heavier trains that will be needed to meet growing passenger and freight demand.

Finding innovative ways to make electrification more affordable and easier to construct is a priority for Atkins. That means taking a fresh look at some old problems.

Avoiding bridge reconstruction is a case in point. Often, bridges over the railway need to be rebuilt to provide extra headroom for new overhead equipment. This is not only disruptive, but also expensive: it is estimated that about 25 per cent of the cost of electrification is for civil works, the bulk of which are related to bridge reconstruction.

One solution to this problem could be to omit overhead equipment altogether beneath bridges, with trains “coasting” through the power gap under their own momentum. Developments in track-to-train communications and smart on-train systems means solutions of this sort are now technically feasible.

A similar approach – using an electrically “dead” section of track – could also make it possible for dual-voltage trains to switch between AC and DC power systems without having to stop. The need to optimise such switchovers is becoming increasingly important as the number of interfaces between AC and DC lines rises.

Developments in battery storage and back-up diesel power could also make a difference, allowing suitably-equipped AC electric trains to operate off the wire. This could remove the need for the electrification of freight sidings and short sections of track, as well as allowing trains to continue their journeys, even with a power failure.

On the fixed infrastructure side, greater standardisation of parts and processes could help to reduce the whole-life costs of future electrification projects, with quicker delivery and easier maintenance.

“Commonality is vital,” says Ducksbury. “For a national electrification programme, you need designs and components that can be widely used, rather than bespoke solutions. Electrification must be safe, affordable and easy to construct – and these are all areas where Atkins offers proven leadership.”

Download PDF