As the tempo of railway electrification in the United Kingdom increases, there is a need to remember that we must acknowledge and gain from earlier experiences.Writes Peter Stanton
It is crucial to benefit from past lessons and apply that knowledge to current and future projects. As most of these are still generally in the design phase, this is the point at which lessons learned can be applied rather than later, when boots are on the ground and rework could be necessary.
With this positive thought in mind, the Institution of Engineering and Technology recently held a seminar in London entitled ‘Railway Electrification – Lessons for the future’ which was attended by a good cross-section of industry players. The day was led by Roger White of Atkins who looked for good ideas, views on costs and a harvesting of experience to identify key factors in taking electrification forward.
Two comes before one
There has been a long history of development of overhead line design, moving from the original works on the West Coast main line in the early 1960s to the more recent West Coast Route Modernisation upgrade and the construction of the Channel Tunnel Rail Link / HS1. There has also been considerable development in mainland Europe and these advances have been reviewed to produce a solid design range for current and future works.
The new ranges for the UK are series two and series one – quoted that way round as two precedes one in development. Series two is in the process of being installed in the North West as part of the project to electrify the route between Manchester and Liverpool along with other associated lines. Series two is suitable for speeds up to 110mph and is not TSI (technical specification for interoperability) compliant.
Series one is being developed by Furrer and Frey with a view to enabling 140 mph running; it will be TSI compliant. The final goal, of course, is to achieve one system suitable for the UK while acknowledging international developments.
In the background also lurks the consideration of what do to with the ageing 650V DC railway.
Noel Dolphin of Furrer and Frey looked forward to the production of a design range which would have its own manuals, convenient sourcing and completed system verification. Naturally this would be a system with enhanced performance, reduced maintainability (vital in a more crowded railway with less maintenance access) and optimum constructability utilising high-output plant where possible. The philosophy of ‘Safe by Design’ will be greatly enhanced by less on-site assembly.
Reviewing auto transformers
To follow that comprehensive review of where electrification is going, the conference was then treated to an excellent paper by Ellen Wintle, senior route asset manager with Network Rail. The subject was the installation of the auto transformer system which was first piloted on the ‘Hilton’ section (Hillmorton to Milton Keynes.), installed on Trent Valley four-tracking and is now proceeding in its phase-three guise on the West Coast main line near Oxenholme. Ellen was determined to ensure that lessons that had been learned from the earlier phases would be adopted and developed within current designs and construction.
Her first reminder was to identify the output and let the design develop in line with that. The original scheme had developed the design in parallel with verification but now there should be an electrification safety case available to all future schemes. An interface management plan would be needed and construction would be managed in line with the ability to access the infrastructure. Commissioning should
be considered during design and previous experience would allow contingencies to be built in. A useful tip was also to make the electrical control room operator your best friend!
As before, Ellen referred to “Safe by Design” and usefully reminded the audience of an incident which had occurred around a piece of switchgear that had never been used – optimise the design and reduce risk by ensuring only essential elements are designed into the system.
The process was neatly summed up in four bullet points:
- Open communication
- Continuous improvement
- Challenge and engage with others
- Share your experiences.
Finally, a very useful reference point for system development is the Rail Electrification Development Programme (REDP). This cross- industry group has been formed to identify and implement initiatives that will enable the industry to meet the challenges of delivering the forward programme of new electrification.
To close, Ellen put the following words up for digestion:
- Understanding performance, operating and maintenance requirements from the outset.
- How do you capture and share lessons learned along the way?
- It’s all about behaviours!
Matters then moved to the London Underground as Phil Carmichael gave the audience a case study on power supply upgrades and lessons learned. The talk was delivered in the context of the plan that all lines would be upgraded in the next 10-20 years, with the sub-surface lines receiving the most extensive upgrade. The system would gain new rolling stock, new track, new signalling systems and enhanced train services, but there would be a corresponding increase in electricity demand of up to 80%.
Technological advances would include raising the traction rail voltage from 650V to 750V, installing composite conductor rails and upgrading rectifier capacity in substations. All of this in a world where the private finance initiative had gone away.
Phil outlined several lessons that had been learned from history. First off was to challenge standards. Requirements may have been in place and accepted by default but, as time moves on, there could be many new options whilst still retaining compliance with safe and effective working.
Secondly, those present were treated to a description of what is known in the underground as ‘Substation Chess’. Previous experience had shown that, with careful planning and staging, the best installation results could be achieved when installing switchgear and rectifiers by continuously creating space in a building and installing in series.
The likelihood is that AC and DC traction systems will continue to run together and what has been described as an ‘inconvenient coexistence’ would therefore still be the case. There has been considerable experience of this inconvenience in recent years and it is painfully apparent that the interface must be considered at the design phase. The transition from AC to DC running is well-understood, but inter-running is not so. Nevertheless, the designer has to remember that, on a DC railway, the running rails are insulated with traction currents of around 2-8 kA whilst on the AC railway the running rails are effectively earthed with traction currents typically around 300-550 amps.
In connection with the thoughts around extending the ‘Electric Spine’ of 25kV electrification to the south coast, these issues have been put together and built into a model which not only has technical value but also identifies risks to the programme, communications and operations.
Analysis leads to change
Once again, the need for a good consciousness of system integration was introduced by Andy Power and Rowan Joachim in regard to the central section of Crossrail. The scale of this development is huge and,
for successful implementation, needs to call upon experience from around the country. A particular highlight was the interface between electrical systems and the combined impacts on bonding and earthing. Initial thoughts were to separate the systems electrically, but analysis quickly dictated that this was just not practicable. There is obviously a requirement to model further and, in particular, confirm that modelling by extensive testing.
Auto transformer feeder systems continue to spread and the programme returned to the subject with Martin Sigrist and Chris Wilson who looked at the Thameslink project. It quickly became apparent that here was a project from which many positive lessons could be learned. As ever, these lessons should be applied during the design phase.
The initial designs and assumptions needed early rework which actually led to a concept rethink and the decision to adopt a completely new strategic approach to switchgear replacement and different approaches to electrical distribution. All of these would have been hugely expensive had procurement and construction phases been under way. Of particular interest was the description of the staging strategy adopted.
The day was rounded off by a panel session led by Peter Dearman of Systra, John Morris of Parsons Brinckerhoff and David Hartland of Brecknell Willis. A lively discussion ensued and the assembled audience finally went home with a robust selection of lessons learned and a consciousness to search for new historical data when preparing their projects!