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LONDON UNDERGROUND & OVERGROUND


Not


only one of the world’s busiest sub-surface railways, but also


the earliest to be electrifi ed, the London Underground system presents some unique challenges – not least due to a long history of underinvestment until Transport for London’s Tube Upgrade Plan. Compounding this is the sheer scale of the traffi c that it handles and the fact that much of the infrastructure is no longer easily accessible – decades of building and over-building have woven it into the fabric of the city.


This being the case, the challenges that faced UK Power Networks Services on the Victoria Line Upgrade (VLU) and those that are now being met on Sub-Surface Railway Power Upgrade Package 2 (SSR2) are not confi ned to electrical alone.


The Victoria Line Upgrade (VLU)


The VLU was part of a wider power traction upgrade programme that prepared the system for new rolling stock that would permit faster station-to-station run times and higher train frequencies. This required increased AC/DC equipment and UK Power Networks Services were responsible for the design, system integration, procurement, supply, construction, commissioning and hand-over at four substations. In addition it also required major cabling works and it was these that posed some of the greatest challenges.


Some 30km of 11kV feeder and pilot cables were needed and barely one followed a straightforward route. They ran along tunnels and rail tracks already congested with cabling; one required installation in a watercourse culvert, laid beneath footpaths and buried beneath major arterial roads.


In addition, the major new equipment included 22kV/11kV 2.5MW transformer rectifi ers, HV, LV and 750V DC switchboards, and a complete SCADA system needed to be installed in areas with limited access and often requiring structural reinforcement.


As a result of the work put into the VLU, London’s passengers now enjoy energy effi cient trains that run more frequently, have greater accessibility, CCTV coverage of the carriages and on-board information systems as well as being brighter, cleaner and altogether more pleasant to travel in.


All this was accomplished on time, on budget and with minimum disruption, which led to UK Power Networks Services being invited to be involved in the next stages of London Underground’s


66 | rail technology magazine Jun/Jul 11


UK Power Networks Services here describes the challenges it faced on the Victoria Line Upgrade and other London Underground projects - and the innovative solutions it came up with to overcome them.


Above: DC switchboard at a traction substation on Victoria line


Below: DC trackfeeder cables at a substation on the Victoria line


modernisation programme – the sub- surface line upgrades. The VLU project had shown that UK Power Networks Services could bring their international resources to bear on the kind of major schemes that modern capital cities need to operate effi ciently and do so in a way that kept the infrastructure running smoothly at all times.


SSR2: a signifi cant undertaking


The sub-surface lines (SSR), comprising the Circle, District, Metropolitan and Hammersmith & City lines are undergoing one of the largest ever upgrades planned on London Underground. UK Power Networks Services is responsible for the SSR2 package of power supply works, of which the electrical infrastructure alone includes two completely new substations as well as 13 signifi cant substation upgrades, 12km of 11kV cabling and over 20km of fi bre optics for advanced signalling systems.


Once again, this has to be carried out in diffi cult working conditions, with many operational changeovers occurring in the hours of darkness, in a way that the general public barely notices. Despite the wide range of the project, not one single shutdown affecting the general public is either planned or expected. Due for


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