The kit preserving electric powered wires above the song within the four-mile (6km) tunnel is failing due to the salty situations below the Severn Estuary.
Network Rail has spent 3 years and what’s concept to be near £20m to put together the tunnel for electrification.
Specialists in electric rail had been delivered in to assist remedy the problem.
The UK Department for Transport has said it’s far “privy to an issue inside the Severn Tunnel works” and insist Network Rail is presently “carrying out investigations to remedy this as speedy as viable”.
Network Rail’s leader working officer Alison Thompson said she is “confident” the primary electric powered teach will run between Cardiff and London early in 2020 – after production and testing takes vicinity q4 and over Christmas and new year.
The line is already electrified among London Paddington and Bristol Parkway
The 133-year-old tunnel between Wales and England has its very own pumping station which brings out an expected 14 million gallons of water (sixty four million litres) a day to save you it being flooded by way of an underwater spring.
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Network Rail conceded it’s miles a “very hard operating surroundings to run 25 kilovolts of electrical through” however insisted trips will now not be affected because the new multi-million trains that serve the direction are diesel and electric hybrids.
Trains journeying into and out of the tunnel could be powered by way of the overhead wires but they will transfer to diesel to journey under the Severn Estuary – so passengers interior will not realize the distinction.
Stuart Cole, emeritus professor of shipping on the University of South Wales, defined the salty situations have been more of an trouble due to the fact the tunnel is not within the outdoors.
He introduced that switching to diesel within the tunnel isn’t always a massive hassle, given the period of a few passengers’ journeys.
“It’s no longer the give up of the sector if they don’t find a answer, but the chances are they may,” he instructed BBC Radio Wales.
Electrification of the south Wales line was supposed to be finished by means of this 12 months however Network Rail final year said it could not give a particular date due to the fact paintings remains ongoing.
The difficulties are the today’s blow to the task, after delays, teething issues for the new trains and the selection to scrap electrification of the road from Cardiff to Swansea.
Former Prime Minister David Cameron introduced the electrification of the Great Western line in 2012 and the tunnel changed into close for 6 weeks in 2016 to begin the electrification venture.
But in 2018, the then UK delivery minister Jo Johnson admitted that electrification device in the tunnel had began to go to pot.
Earth straps – a protection function at the overhead connectors maintaining up the energy line – have been corroding inside the salt water environment within months when they’re alleged to have a 25-12 months lifespan, that means the line thru the tunnel could not be electrified competently.
It means the electrification machine within the brickwork tunnel – the longest underwater tunnel within the world for greater than 100 years after it opened in 1886 – struggles to preserve voltage and frequently trips.
Network Rail shriveled experts from Swiss enterprise Furrer and Frey, specialists in developing strength cables inner tunnels, to design a solution however none have so far labored inside the salty weather.
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Engineers need to affect the line to carry the new bi-mode Hitachi trains – a part of the United Kingdom government’s £5.7bn educate fleet – which entered carrier in 2017.
“The new intercity electric powered trains function in both diesel and electric powered,” said a Network Rail assertion.
“Their operation via the tunnel isn’t affected and we are on course to introduce the new better timetable in December 2019 that is the end result of the modernisation and electrification over the last few years.
“The timetable will deliver large blessings to passengers in south Wales, with reduced adventure instances of up to 14 mins to London and considerably improved capacity.”
Franchise holders GWR may be operating electric powered trains thru the tunnel and say they’re “conscious” of Network Rail’s upgrade, however insist the works remain on track to allow them to introduce their advanced timetable in December.
The Welsh Government said Network Rail had confident them the problem could not have an effect on passengers.