Railway tracks

Rail electrification: Engineers consider the overheads

The challenges of a railway upgrade scheme are as much political as technical, writes Lorna Sharpe.

The question of replacing the ‘third rail’ electrification system on south-east England’s railway network with overhead wiring has received new attention recently, both from within and outside the industry.

In a report on transport preparations for winter weather, published early this year, the House of Commons Transport Select Committee reiterated its view that the government should push for the planned conversion of the Southampton to Basingstoke line to take place speedily, so the benefits could be evaluated and a business case built for further conversion.

It isn’t that simple, though. The report was a follow-up to one on the problems caused by ice and snow. Better performance in hard winters would be a benefit of conversion, but it’s not a sufficient reason for doing it, and the challenges are considerable.

So why is the idea even under consideration? What we have - 750V DC supplied through top-contact conductor rail - is old and is reaching the limit of its capacity, and running costs are high. Moreover, much of the DC distribution equipment will soon need replacing, which creates an opportunity for change.

Industry researchers looked at various possibilities and, in a paper published by RSSB in August 2011, concluded that the preferred option would be to replace the DC system with overhead distribution at 25kV AC. Benefits include reduced cost, taking into account energy use (and losses), maintenance and renewals, as well as better train acceleration (which shortens journey times), increased capacity and reduced risk of electrocution.

The authors of the RSSB report, known as T950, called for development of an industry business case and a potential implementation plan as next steps.

Implementation is where engineers come in. At an IET seminar in December, a panel of railway electrification specialists led a discussion on the key challenges to electrifying the southern region at 25kV.

John Morris of Parsons Brinckerhoff, who is engineering director for the Great Western electrification project, began. “You can imagine that if the conversion is done progressively from the outside inwards (doing the hard parts last), there will be a significant number of limited-duration AC-DC changeovers in place for 10-20 years” he warned.

“There are issues with the changeover itself and sections of dual AC-DC running. There are questions of automatic changeover, changeover on the move, multiple pantographs and the space required to incorporate these, questions of how these might be moved along from one location to another as the electrification continues. There will be temporary areas with dual AC-DC electrification while testing takes place.”

However, Morris said, it is the operational and political issues that are significant. “There’s a patchwork quilt of interfaces, stakeholders, operators, different interests across this project. What we’re talking about here is a system. You can’t optimise a system by optimising the subsystems individually.

“We can only get this programme right if it’s dealt with as a whole railway system. We need an executive authority that can make things happen on a whole-system level. I do not see such an arrangement in the UK.”

Dave Hartland, engineering director of Brecknell Willis, also sees a combination of technical and political challenges, but from a different direction. Putting in overhead lines will need a major programme of civil engineering works. That will be expensive and disruptive, so planning consent will be an issue.

“It would only take a small number of politically astute or maybe wealthy individuals in the southern part of England to object vociferously to sway the government. We would need huge political support, and that political support depends very much on what is put up outside your front door or what roads are closed during the conversion.”

The final speaker was Peter Dearman, head of network electrification at Systra. He is in no doubt that the programme should go ahead. Faced with the question of practicality, he said we have to ask how practical is the idea of not replacing the conductor rail: “Where does that leave us with the main line network south of the Thames? Unable to accommodate extra growth in any sensible way.”

Dearman is used to dealing with people who point out the difficulties. “One of the stumbling blocks is the London area. From Clapham Junction inwards, it is difficult to see how to manage the conversion. But the sections where we need the speed and extra traffic are the outer parts. So let’s move from the outer parts inwards. Worry about that when we get there.”

Of more concern is how to manage the changeover. There are precedents, though. Some lines between London and Essex were converted from overhead DC electrification to AC in the 1960s, with the final transition happening over one weekend.

“If they could do it then, why are we so jittery, as engineers?” Dearman asked. “Are we more stupid than our predecessors? I don’t think we are. We just have to work out how to do this.”

Dearman’s answer is that the industry needs to convert a minor route as a pilot.

So where does that leave the Southampton to Basingstoke line, which the government nominated as the pilot scheme? “As the oil price doubles by mid-century, diesel for freight will be unaffordable,” Dearman said. “The Southampton line is essential - but I am arguing that it shouldn’t be the pilot. Do it somewhere else first.”

However, it’s still far from certain that the wires will go up across south-east England.

The authors of the RSSB report were tasked with identifying a preferred option, but added the caveat that “the affordability of the change has yet to be determined”.

Dave Ward, Network Rail’s route managing director for London and the south east, told the Transport Select Committee that the likely cost would be “billions of pounds”, and that it would be for the government and the Office of Rail Regulation to decide whether it was a good use of public funds.

E&T asked Dearman if he was confident that the politicians would agree to the conversion.

“I’m confident as it’s possible to be that they’ll find it hard not to agree,” he replied, “unless they’re saying that there’s no future for rail.” *

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