solar storms a concern for signals?

[whole diary]

[infoman]

https://www.independent.co.uk/news/science/lancaster-university-earth-lancaster-glasgow-preston-b2122573.html

[Electric train]

https://www.independent.co.uk/news/science/lancaster-university-earth-lancaster-glasgow-preston-b2122573.html

Can just see the headlines .......... to miss quote the 11 Feb 1991 BR^▸ (British Rail(ways)) Director of Operations, Terry Worrall .......

"The wrong kind of sunshine" 

[Mark A]

Yup. Not sure it's possible to even predict what a solar storm on the scale of the most notorious, the 'Carrington event' back in was it 1853, would take out. Not sure either of the extent to which the railway made use of electricity at that date either, if anything. If they *did* they'd have had early experience.

Mark

[stuving]

This report (and others elsewhere in the media) comes from a press release from the National Astronomy Meeting (NAM 2022) being held this week at the University of Warwick:

Space weather will delay your trains
Royal Astronomical Society press release
RAS PR^▸ (Public Relations) 22/22 (NAM 9)
13 July 2022

Fluctuations in space weather are disrupting train signals and causing significant delays. A project investigating the effect of solar storms on railway signals will be presented this week at the National Astronomy Meeting (NAM 2022) by Cameron Patterson, a PhD student at Lancaster University.

The sun’s tendency to affect technology on Earth, as well as in space, is known as space weather. In railways, electric currents caused to flow in the earth by solar activity can interfere with the normal operation of signals, turning green signals to red even when there is no train nearby.

Patterson says: “Most of us have at one point heard the dreaded words: ‘your train is delayed due to a signalling failure’, and while we usually connect these faults to rain, snow and leaves on the line, you may not have considered that the Sun can also cause railway signals to malfunction.”

To track the location of trains, a railway line is split into small, consecutive segments called ‘blocks’ with an average length of 1-2 km. Each block is tied to a signal that tells you if there is a train currently in that block. The signals are controlled by relays which detect currents in the system. Synonymous to traffic lights, the signals turn green if the block is empty and a current is detected, or red if the block is occupied and no current is detected.

Solar storms can off-set the balance of currents controlling the light signals on train lines, causing lights to show clear sections as occupied with a red light. Evidence shows that stronger solar storms cause more signals to malfunction, thus increasing the amount time the train is delayed.

A team of researchers at the University of Lancaster have modelled the impacts of solar storms on two segments of the UK^▸ (United Kingdom) railway network: a South-North line from Preston to Lancaster and a West-East line from Glasgow to Edinburgh.

Technological problems can occur as a result of solar storms with a range of strengths: from medium storms with electric field strengths of 2V/km to strong storms at 4V/km. In the past, values of higher than 7 V/km have been detected along railways in Sweden. Estimates of extreme solar storms have predicted events with strengths of up to 20 V/km.

Interestingly, the results suggest that signalling failures can occur even with moderate storms. So, while these estimates are unsettling, there is still cause for concern without these extreme storms.

Describing the future of his work, Patterson says: “We are now working on looking at the case where trains are present on the line, and how strong a storm needs to be to turn a red signal back to green - a far more hazardous scenario potentially leading to crashes!”

I read that as saying he is looking at the effect of "electric field" on track circuits, though would be a big jump from saying that happens to saying it causes wrong-side failures (which I don't think he is). I think this "electric field" is the voltage gradient along the line due to the geomagnetic current and the ground at the transient geomagnetic field due to the solar storm. If the Earth is a uniform conducting sphere these two effects should balance each other; it's not so they don't.

I have not yet worked when this work was - or if tomorrow will be - presented at the meeting, or what form of presentation is involved.

[TonyK]

We may not have experience of massive solar storms and their effect on the railway, but we are not short of experience of signal failures. Any effect will last a day or two at most, and will leave no more lasting damage than the present malign effects of rats, water, cable thieves et al.

I propose we do nothing.

[broadgage]

Solar storms can not be forecast far in advance. A suitably placed satellite can give some near term warning.

At the time of the Carrington event, railways were starting to use electric telegraphs, as was the wider world. Telegraph equipment was damaged and telegraph offices destroyed by fire.

A similar event occurring today would be hugely destructive to modern infrastructure. As well as damage to electrical infrastructure, other long metallic structures are vulnerable including long wire fences and long pipelines.

The effect on railway signaling would be very severe, but this may be less important than it sounds. A modern day Carrington event would result in enormous disruption with much of country lacking food, water, fuel, and modern communications.

It is unlikely that electricity would be available to power electric trains. Diesel or steam engines could run if fuel was available. Modern signaling would have to be dispensed with, alternatives include;
Time interval working.
"one engine in steam" working.
Manual token working.
Something similar to block working but with two way radio replacing bell signals

Some relaxation of safety standards would have to be accepted. Put VERY bluntly, who would care about the odd railway accident when millions of lives would be lost to the wider disaster.

Another Carrington event is inevitable, but we have no experience from which to estimate the probability.
Worst case could be several times in a century ? in which case we have had a very long run of good luck and a repeat is likely in the lives of all our younger members.

Best case would be that such events are very rare, occurring only once on average in many thousands of years, in that case it COULD happen again tomorrow, but probably wont.

[broadgage]

We may not have experience of massive solar storms and their effect on the railway, but we are not short of experience of signal failures. Any effect will last a day or two at most, and will leave no more lasting damage than the present malign effects of rats, water, cable thieves et al.

I propose we do nothing.

I disagree with the first part of the above. I consider that a lot of modern solid state signaling equipment will be destroyed, by excessive voltages introduced into it by long external conductors.
I would expect that the effects would last months or years, not a day or two. How long to manufacture replacement electronics ? Remembering that the factories need electricity, raw materials, and other inputs.

Perhaps surprisingly I agree with "do nothing" simply because not much CAN be done. Stocks of spare signaling equipment only help a little as technology advances and reserve stocks would soon become outdated.

[broadgage]

A solar storm is expected tomorrow, Wednesday 03/08/2022.
Details from news media of your choice.

My PERSONAL view is that serious or widespread consequences are unlikely, but soon we will find out !.

Some disruption to radio communications, GPS signals, and to large grid systems is possible. It is well to be prepared just in case the consequences are more serious than expected.

[broadgage]

As predicted, nothing much happened. No doubt someone somewhere experienced some disruption, but AFAIK^▸ (as far as I know) no significant or widespread effects were observed.

A future solar storm could be much more severe and could result in substantial loss of life, so it is well to remain prepared for a solar storm or any other out of course event. This one was a non event.

[ChrisB]

Strangely, they’ve ALL been a non-event to date….

[broadgage]

Strangely, they’ve ALL been a non-event to date….

And MOST solar storms in the future will also be a non event.
There is however a small but real risk of of a severe solar storm resulting in large scale loss of life. It might happen in a months time, or maybe not for a century or more.

[ChrisB]

So minute that no one bothers to prepare for it