13.07.17
East meets west
Source: RTM Jun/Jul 17
Louise Moore, engineering manager for HV power at Crossrail, tells RTM how two great railways will be joined by electrifying at 50kV under central London.
A dedicated team of engineers is working around the clock on Crossrail – Europe’s largest infrastructure project – to install the 5.5MW per train traction power supply to the new Elizabeth Line trains. With the new railway, which opens fully in 2019, running over 100km from Reading and Heathrow in the west to Shenfield and Abbey Wood in the east, the Great Eastern and Great Western main line electrified networks will be joined under central London, connecting new and existing traction power systems through 42km of new tunnels for the first time.
Elizabeth Line services through central London will operate from December 2018 and “the technical complexities of seamlessly integrating the existing Network Rail 25kV electrified open route systems at either side of the new railway, with the new 25-0-25kV Elizabeth Line sub-surface system, provides a multitude of challenges for all involved”, said Louise Moore, engineering manager for HV power at Crossrail. “The project requires a great deal of co-ordination between the Crossrail, Network Rail and National Grid teams.”
The electrification system for the new sub-surface central section of the Elizabeth Line, from Paddington to Abbey Wood, consists of four key locations from east to west:
- Pudding Mill Lane Bulk Supply Point (BSP) and Autotransformer Feeder Station (ATFS)
- Stepney Green Autotransformer Site (ATS)
- Westbourne Park ATS and Kensal Green BSP and ATFS
- A further ATS at Plumstead in south east London
The main power supply for the central section is located at Pudding Mill Lane in the east. In order to deliver this, National Grid has been contracted to provide the main BSP by connecting into its 400kV network and to provide two 88/104MVA ONAF 400/50kV traction transformers. “At the same location, we’re building a new ATFS to feed the Elizabeth Line tunnels as well as Network Rail’s Great Eastern Main Line,” explained Moore.
“The Great Eastern Main Line is currently electrified using a classic 25kV AC system and will be converted to a 25-0-25kV system as part of the upgrade which is necessary to supply the Elizabeth Line trains up to Shenfield.”
The power is then distributed from Pudding Mill Lane through the new Elizabeth Line tunnels to the west and south-east sections of the railway.
“It’s not possible to use a conventional overhead catenary system (OCS) so a rigid overhead conductor (ROC) beam system has been employed extensively for the first time in the UK. This technique has only previously been used in short lengths in the Thameslink tunnels, some depots and swing bridges,” noted Moore. “The conductor beam is made up of extruded aluminium in which is inserted a 150mm copper contact wire. This contact wire is also used in the conventional flexible overhead contact system, which provides a smooth interface with the Network Rail OCS at the east and west ends of the tunnels.”
Stepney Green is the only sub-surface ATS. Here, there are two outdoor 15MVA autotransformers with indoor metal clad gas insulated switchgear.
Heading west of Stepney Green to Westbourne Park, an outdoor ATS will provide an alternative 25-0-25kV supply, from Kensal Green ATFS constructed as part of the Crossrail programme by Network Rail for the Great Western Electrification Project. Included in these works are the two 25kV circuits that supply power to Westbourne Park.
The Great Western Main Line is also in the process of being converted by Network Rail from a classic 25kV AC system to a 25-0-25kV autotransformer system, as part of the Old Oak Common and Paddington Approaches and Great Western electrification projects.
“Paddington is a key interface point,” said Moore. “It’s the lynchpin between our works, National Grid’s West London Upgrade, Great Western electrification, Old Oak Common and Paddington Approaches, Network Rail and London Underground’s sub-surface Four Lines Modernisation programme. Each could ultimately impact on the Elizabeth Line electrification. Works such as power, OCS, earthing, track and signalling system upgrades are going on while existing services must not be affected from Paddington, and National Grid continues to provide power to west London. On top of this, joint commissioning sessions are required.
“The key is timing and synergy; each project has dependencies on the success of the others.”
Last but not least, on the south-east section of the Elizabeth Line route, where the services will terminate at Abbey Wood, is the Plumstead outdoor ATS with two 15MVA autotransformers. This provides 25-0-25kV supply to Abbey Wood station.
Joint commissioning events between Crossrail, National Grid and Network Rail have already started at Kensal Green and Pudding Mill Lane. Commissioning will then continue apace through the new Elizabeth Line tunnels in the run-up to testing and passenger trains running from December 2018.
FOR MORE INFORMATION
W: www.crossrail.co.uk