SEVERN TUNNEL OVERHEAD IS A PROBLEM
NETWORK RAIL has confirmed that electrification at Cardiff Central station and most of the approach from Newport will not be ready for use this year. It is also unable to say when the 25kV equipment in the Severn Tunnel will be energised.
Previously the expectation was that the entire electrification between Bristol Parkway and Cardiff Central would be ready for use in December. In late June, Network Rail said: ‘We have amended our schedule of delivering electrification to Cardiff. Electrification to Newport will be delivered ahead of the December timetable as planned but the 10-mile stretch to Cardiff, which will be built by November, will now be tested and switched on over the Christmas and New Year break.
‘The new schedule for testing and switching on electrification to Cardiff has no impact on the new December timetable changes as GWR’s bi-mode trains can run on diesel between Newport and Cardiff until January, when electric services will start to Cardiff.’
Great Western Railway is pressing ahead with its plans to introduce a post-electrification timetable in December (p62).
Earlier this year, managing director Mark Hopwood said the planned journey time improvements could be delivered reliably with or without completion of the South Wales electrification by December, thanks to the lively performance of Class 800 units under the wires east of Bristol Parkway (p8, April issue).
In June, Alison Thompson, chief operating officer for Network Rail Wales and Borders, said: ‘We are really focused on the smooth introduction of the new timetable in December. The new timetable will bring passengers more frequent [trains], new services and faster journeys [and] provides more capacity on busy routes like Cardiff to Taunton via Bristol.’
SEVERN TUNNEL UNCERTAINTY
In early July, Network Rail was unable to say when the 25kV supply in the Severn Tunnel would be switched on or to provide details about any additional possessions to prepare for energisation. The tunnel’s Overhead Line Equipment (OLE), featuring aluminium conductor rail, was installed in summer 2016 and has already required substantial modifications. The copper contact wire has been replaced with aluminium, following signs of bimetallic corrosion where the copper wire met the aluminium rail. This is the UK’s first use of aluminium contact wire, which has a potentially shorter lifespan than copper.
The concentration of pollutants from diesel exhausts and coal dust, along with saltwater ingress and the tunnel’s dampness, are causing difficulties not encountered in any other electrified railway tunnels in Europe, according to a source who said the conductor rail will require cleaning following three years when the OLE was in situ but not used. This is no minor task, there being approximately 14km of conductor rail in the tunnel.
It is understood that the earth straps, each about 30cm long, will be replaced with straps which have improved sealing against corrosion. Rhodri Clark