Following energisation of the overhead line equipment between St Brides, Newport, and west of Cardiff Central, the first GWR electric train arrived at Cardiff on Tuesday 7 January 2020. This was the culmination of the major portion of a truly strategic electrification project as Brunel’s Great Western Railway route to Wales finally joined the ranks of electrified main lines in the United Kingdom.
The project has been running for some time. Originally announced by the Labour government in 2009, the line would be fully electrified to both Bristol Temple Meads and Swansea “within eight years”.
After the election of a Conservative/Liberal Democrat coalition in 2010, the programme was reviewed. In November 2010, electrification was confirmed from London Paddington to Didcot. In March 2011, this was extended to Bristol Temple Meads and Cardiff, including the line between Bristol Temple Meads and Bristol Parkway. This was extended from Cardiff to Swansea in July 2012.
As is now well known, the project ran seriously late and over budget. While electrification to Cardiff would continue, it would not reach Bristol Temple Meads as the sections from Bristol Parkway to Bristol Temple Meads, and from Thingley junction (Chippenham) to Bath and Bristol were to be “deferred indefinitely”. Cardiff to Swansea electrification was cancelled in July 2017.
Still, the main part of the project continued. Electric running from Paddington to Didcot was introduced in January 2018, then to Swindon and as far west as Bristol Parkway in January 2019. The same month saw electric services between Reading and Newbury. Electric running to Newport commenced in December 2019.
Work continues between Swindon and Chippenham, and there is a significant technical challenge to overcome in the Severn tunnel, where Network Rail and its project partners are working hard to overcome challenges caused by unusual conditions inside the tunnel.
Rail Engineer was invited to the Network Rail office in Cardiff to meet David Hewing, the electrification and plant lead engineer for the Wales and West Route. David has been involved with the Great Western Project since its inception in 2009, first taking the client technical role, then supporting system design and finally enabling the scheme to be taken into operation and maintenance by the Network Rail route. He was pleased to relate the story of how the current stage was reached, summarising the various challenges and opportunities along the way.
Historical background
At the start of the 21st century, the Great Western main line was one of the last two of the major main line routes in the UK using diesel as the main source of traction power. When the announcement was made in July 2009 to electrify the Great Western (along with the Liverpool-Manchester line), it represented the first big rail electrification project in the United Kingdom for around 20 years.
The South Wales section of the Great Western Main Line was set to be the first significant electrified cross-country railway mainline in Wales.
Prior to 2009, the only electrified portion of the Great Western was between London Paddington and Airport Junction (west of Hayes & Harlington station). This portion is equipped with a 25kV AC overhead system which was implemented in 1997 in readiness for the Heathrow Express service that commenced early in 1998.
Electrification was extended from Airport junction to Maidenhead under the Crossrail scheme. Further electrification west of Maidenhead was announced by the DfT separately, though the work west of Airport junction (to take Crossrail to Maidenhead) and west of Maidenhead was to be undertaken as one scheme.
The parallel plan to upgrade the rolling stock on the Great Western was included in the Intercity Express programme announced in 2007, a Department for Transport (DfT) led initiative to replace the ageing fleet of InterCity 125 (HST) and InterCity 225 train sets then in use on much of the UK rail network.
Planning Construction Methodology
As this was the first major electrification schemes in the UK for a long time, thoughts turned to more productive methods of electrification than had been previously applied. Safety risk assessment had also shown that a more rigorous attitude to construction safety was required and the result was the High Output Plant System (HOPS) train, used for the project to electrify the Great Western main line.
Based at the High Output Operations Base (HOOB) in Swindon, the £40 million state-of-the-art HOPS train built a significant proportion of the overhead line equipment (OLE) on the route. The train works for seven to eight hours – depending on where it is being used – for six nights a week. With a top speed of 60mph while travelling to the worksite – but only 5mph during a possession, or 15mph if it is the only activity on site – the HOPS train can build the electrical contact system and associated infrastructure at an average of around 1.6km per night.
However, the high output plant is not suitable for all aspects of an electrification scheme and alternative methodology has also been implemented across the project, with lessons also being learned on the use of the train itself.
The Project
Much has been said about the cost and timescale of the scheme. Having worked on it since its inception, David was able not only to review lessons learned but also the not-insignificant successes and sheer achievement of the works.
The Great Western scheme progress has to be looked at in the context of the long gap between previous major electrification schemes and the need to regenerate the skills and knowledge that had faded away in the meantime. A major national programme of electrification had been proposed in 1979 that would have progressively electrified all significant routes in the country, but the proposal was not taken forward.
A programme of electrification is not just about the core electric traction equipment, it also involves signalling, control system immunisation and gauge clearance. These require considerable design, construction, and commissioning work on top of the basic electrification.
Several noteworthy innovations, that utilise state-of-the-art design methodologies and apply current international standards, have produced a very resilient system. This had been amply demonstrated recently when the system was run, on a full weekday timetable, with one new feeder still not available for service and it still achieved contact system voltages across the project that complied with the Technical Standard for Interoperability.
The new feeder at Bramley has yet to be commissioned and, although sited off the main route on what was the now-cancelled Reading to Basingstoke electrification, will provide extra resilience for not only the GW scheme but Crossrail as well.
At the London end of the line, power is taken from Kensal Green, which is integrated with supplies for Crossrail.
In fact, the traction supply side of the system has the capacity to deal with, not only the original scope that has currently removed from the scheme, but also any further expansion that may be required.
This excellent performance has vindicated the decision to go forward with an autotransformer (AT) system, which is much easier to install in a new electrification scheme such as this one than to retrofit into an existing system. However, AT is not necessarily the universal solution for all lines and it is interesting that, for the Reading to Newbury portion, a classic system has been designed.
David also suggested that having a robust relationship with National Grid had assisted in achieving both good electrical performance and achieving a cost of power provision in line with original estimates.
RATS
In 2014, ABB and its partner UK Power Networks Services were appointed to deliver the trackside power infrastructure for the modernisation programme. During the project, ABB’s scope included designing and delivering 31 trackside feeder substations along 235 miles of electrified track between London Paddington and Cardiff. These receive power from National Grid’s 400kV network and step it down to a 25-0-25kV power supply for catenary lines.
The conventional approach to rail electrification is to divide the railway line into sections, each of which is controlled by at least one circuit breaker. However, Network Rail’s design engineers spotted the potential to reduce costs during the early stages of the project by using load-break switches instead of circuit breakers in some instances. Less costly than circuit breakers, load break switches are not designed to tolerate high-level fault currents.
To enable the use of load break switches, Network Rail put together a new concept called the Rationalised Autotransformer Scheme (RATS). This is an innovative approach to protection and control based on IEC 61850 smart grid communications.
Under RATS, load-break switches are protected from ever experiencing high-level fault currents by circuit breakers. These are controlled by Intelligent Electronic Devices (IEDs) that will open circuit breakers when a fault is detected. In the case of a fault, communication between the IEDs will identify its location to within a few kilometres. The scheme will then reconfigure the network to isolate the fault and re-connect healthy sections of track. This three-stage process of tripping, reconfiguration and restoration must all take place within a few seconds.
The RATS concept minimises the length of track affected, as well as the resources needed for inspection, rectification and restoration of power to the railway lines. The overall result is less outage time and shorter possessions, with less risk to operating staff working along the rail corridor.
RATS uses digital communication over fibre-optic lines, based on the IEC 61850 protocol – the international standard that governs the protection and control of substation automation equipment. It is based on the philosophy of using a single future-proofed communication protocol, a common format for storing data and compatibility across equipment that has been supplied by different vendors.
Also mentioned was a new approach for GWEP in the form of ABB SMOS (structure-mounted outdoor switchgear) Light. This modular switchgear is designed for straightforward installation and maintenance at trackside substations.
The switchgear is delivered to site as modules that are ready to plug and play. It integrates all the components required to isolate the power supply to the catenary line and to sectionalise individual parts of the track for maintenance and inspection. Individual components are all factory-mounted on a steel structure.
Integrating the FSK II+ (frequency shift keying) into the SMOS Light concept has reduced project risk and cost in the construction phase of rail electrification projects. It saves time on-site by up to 30 percent as there is no need to install and commission separate components.
A major benefit for Network Rail is its use of vacuum as an insulating medium. This eliminates the need for SF6 (sulphur hexafluoride) gas in trackside substations. As this gas has an elevated global warming potential, adopting vacuum-insulated switchgear supports the operator’s environmental credentials.
While RATS was developed for use with autotransformer systems, the concept provides significant efficiencies for both classic 25kV and autotransformer 25-0-25 kV system designs. Network Rail is now looking at how this may be employed to reduce electrification costs on new systems. This was obviously a bold move to introduce to the project but did not, in fact, increase substation costs.
Contact system
Another result of the long gap between electrification projects was that the standard British overhead line contact system was out of date. The Mark 3 system dated back to 1974 while the newer UK1 was designed for the West Coast Route Modernisation that took place between 1998 and 2009.
For the Great Western scheme, Network Rail decided to have a complete rethink on contact system design, one suited to the high-speed requirements of the new project (reputedly defined by the Department for Transport as having to power trains travelling at 140mph and fitted with two pantographs). The new Series 1 concept set out to remove what had been viewed as points of weakness in the Mark 3 design. The opportunity was also taken to optimise the design to the use of the high-output system for installation. Development took longer than expected and an alternative system for non-high-speed lines was put in place for the North West electrification and similar schemes.
Much has been made of the apparent size and presence of the Series 1 system, but David emphasised that, on open line, the system is quite unobtrusive – the bulky nature becomes more apparent in four-track areas. Newer installations certainly seem to look less obtrusive than earlier, with lighter fashion OLE structures.
Similarly, foundations were initially designed from first principles without considering previous industry electrification experience, resulting in piles 12 to 15 metres long, which caused significant installation problems. This was addressed by a new 2017 standard that regularised previous empirical methods, as described in our feature “Getting electrification right” in issue 164 (June 2018). As a result, Network Rail now adopts some of the risk in application of design codes by contractors.
A further gain has come from the intense work and evaluation of clearances and a better understanding of the risk associated with lower clearance. Work was first concentrated on the intersection bridge at Cardiff, where a re-evaluation resulted in a significant economy in the electrification provision. Reduced clearances have been specified and obtained with a better understanding of the risk from overvoltage and Network Rail’s development of guidelines for the use of surge arrestors. Work as Southampton University has also crystallised design clearance calculations and robust insulating coatings have built up a further low-risk profile.
Development of electrification has looked at motorised switches for some time and the application has approached maturity on the Great Western scheme. A reliable indication for the position of switches has now been achieved and a wide-ranging review of switching and sectioning arrangements has again reduced the need for staff on site to wrestle with manual switches; retaining manual application if the site is one where the staff will need to be anyway. Earthing and switching arrangements have been revised but the system still requires the comfort for a maintainer of a visible earth adjacent to their workplace.
The Severn Tunnel
In view of the restricted clearance and general environmental position in this unique and historic tunnel, a decision was made early on to install a rigid overhead contact system (ROCS). From historic experience, the extremely wet nature of the tunnel was well known and over 150 years of steam and diesel traction had left their polluting mark. A Furrer+Frey ROCS system was designed and installed in the tunnel, building on the company’s extensive experience in tunnel contact systems.
However, once installed, the installation began to degrade in an unexpected manner. Some galvanic action had been predicted, but one of the Severn Tunnel’s unique features is that most of the extremely wet conditions are due to the Great Spring, a source of fresh water, not salt.
The level of degradation was far greater than had been anticipated, and could not be blamed solely on galvanic action stemming from the wet conditions. Experts were called in, and the cause was identified as a form of anaerobic sulphur-reducing bacteria, more usually encountered ion North Sea oil platforms.
Noel Dolphin of Furrer and Frey explained that aluminium is normally passivated (protected) by the formation of oxide on the surface – once the oxide layer is formed the system stabilises and very little further deterioration occurs. However, the bacteria consumes the oxide layer, exposing bare metal and allowing it to oxidise again, whereupon the bacteria once again consumes it.
This endless cycle never allows the aluminium to form a stable oxide layer, so it is slowly and totally consumed. In addition, having bare aluminium exposed exacerbated the galvanic effect of having the aluminium support structure in close proximity to the copper contact wire.
Furrer+Frey and Network Rail tackled this challenge by replacing the normal copper conductor in the ROCS with an aluminium conductor, thus reducing the galvanic effects. The material of other components was also changed and the whole charged to judge its ability to stand up to the atmospheric conditions. Whilst trains continue to traverse the tunnel on diesel traction at the moment, Network Rail predicts that the system will succeed in holding charge and the aim is to energise the tunnel in the next few weeks, though it won’t be used for electric traction until the current collection system is proven.
A further, more conventional civil engineering solution has also been adopted. Drip trays have been fitted where there is salt-water ingress from the Severn Estuary to avoid direct contamination of the ROCS and this is anticipated to slow down degradation further.
Steventon Bridge
Collin Carr reported in issue 167 (September 2018) on the problem of Steventon bridge. This Grade II listed structure, approximately 4.5 miles west of Didcot station, is an elliptical three-arch brick overbridge which carries the B4017 over the GWML, linking the two halves of the village.
Although Network Rail wanted to demolish and rebuild the bridge to give clearance for the overhead wires, this was fought by the local population as the village would be cut in half for 10 months while the work was carried out.
With two nearby level crossings preventing excavation to lower the track, and no way to safely run live OLE through the bridge as it stands, trains currently have to go through it under diesel-power, so stymying the railway’s ambition to run electric-only.
However, a team from consultant engineer Atkins now believes it has managed to find a solution. Hopefully, Rail Engineer will bring you more on this in the coming months.
Wales Electrified
Talking to David it was clear what a challenge this scheme had been, particularly as it marked a return to significant mainline electrification after a gap of over twenty years.
However, now that electric trains have arrived, Wales can feel proud to be part of this resurgence. The scheme massively increases the percentage of the UK railway that is electrified and it can only be hoped that, in the light of increased environmental awareness, the lessons learned from this scheme can be applied further in England, paralleling the robust growth of electrification in Scotland.
Thanks to Dean Shaw, senior communications manager, and David Hewings, lead engineer, both of Network Rail, and Noel Dolphin of Furrer+Frey, for their assistance in preparing this article.
