Rail network disruption from outer space

Les McCormack | 27 Apr 2017 | Comments

In the early hours of 13 March, 1989, a space weather event caused a nine-hour power outage in Quebec, Canada. A solar wind storm induced such intense currents to flow in Hydro-Québec’s power lines that circuit breakers across the network began to trip. Ninety seconds later, the entire power grid had been rendered inoperable. This one space weather event caused CAD$10 million worth of damage and left six million people without power over night.

The event prompted a number of governments to study the effects of space weather on their power infrastructure. In the UK’s National Risk Register, space weather now ranks lower only than pandemic flu in the potential severity of its effects and is considered more likely than a major flooding event. In the United States, the National Academies of Sciences has estimated that a severe space weather event would cost the country $2 trillion in the first year alone – that’s 20 times the damages of Hurricane Katrina. But there remain areas and sectors where its impact is still uncertain.

Domino effect
The study of space weather effects on infrastructure is relatively immature, so we don’t know what the impact could be in certain sectors. The UK rail network, for example, is a very large, complex transit system, with around 12,000 single track kilometers of electrified rail lines. This lack of certainty regarding the impact of space weather on infrastructure prompted Atkins to author a pioneering report on the subject, in conjunction with RAL Space, a scientific research laboratory, and The University of York, both based in the UK.

The study identified several elements in railway networks as potentially vulnerable. First, there is the question of power: if the electrical grid goes down, normal railway operations would be severely affected. The good news is that the UK’s National Grid has a strategy for hardening their infrastructure against severe space weather. For example, during current and future upgrades, the large transformers will be made more resilient to space weather. Where specific assets have been identified as vulnerable, the National Grid has looked at how to re-configure the system to make it more robust.

There are also specific responses lined up in the event of any anticipated major space weather incidents. All maintenance would be cancelled, for example, and assets would be switched in to spread the load of any “phantom currents”.

Even if the electrical grid stays up, trains could still lose power due to space weather. Transformers on the railway network distribute power up and down the line; lose these and electric trains will grind to a halt just as surely as if the entire grid had failed.

It should also be noted that disruption scenarios could escalate quickly. In the event of a severe space weather event, many things we rely on in our day-to-day lives could be affected across our infrastructure, not just within the railway, and these combined effects on resilience need to be understood and planned for.

Even if the trains could somehow limp into a nearby station, the stations themselves need electricity to run the lifts, ticket barriers, information screens, lighting – overcrowding could become a real concern very quickly.

And if the power stays up and the trains keep moving, there are other potential problems – disruption of train detection systems, for example. In most cases, railway networks are divided into fixed blocks and managed using a signalling system. Signalling systems typically rely on some form of train detection to know when trains have entered or left a block. A common form of train detection, the track circuit, uses a small current in the rails and when a train enters a block, its axle shunts the circuit. The signal guarding the block then turns to red to show that the block is now occupied. When the train leaves the block, the circuit is no longer shunted and the signal returns to unoccupied. Some track circuits could be vulnerable to geomagnetically induced currents, present as a result of space weather, and interference to track circuits in Russia and Sweden, thought to have coincided space weather events, have previously been reported.

And modern signalling innovations are not necessarily less vulnerable – in Europe, a new initiative known as the European Rail Traffic Management System (ERTMS) is being introduced. This can use moving block signalling where the safe distance required between trains is based on their speed and ability to brake. It is more efficient because more trains can be added to the network, but it relies on knowing exactly where the trains are on the track and how fast they are moving at any time. In some configuration states of ERTMS such information is collected using GSM-R, a railway specific adaptation of the mobile phone technology which many of us carry around in our pockets. In the future, a Global Navigation Satellite System (GNSS) may also be used to locate trains. Both GSM and GNSS technologies can be affected by space weather.

Then there is the elephant in the room: single event effects. These are thought to occur when a high-energy particle from the solar wind makes it to the ground and passes through an electronic circuit. This could cause havoc by triggering them to do unexpected things. The problem is that the effects of these events, and the mechanisms by which they happen, are not well understood, so investigating them is extremely difficult.

Next steps
Atkins’s research largely focused on the effects of a modern re-run of the most severe space weather known to date. Called the Carrington event, it took place in September 1859, when the aurora covered two-thirds of the Earth’s skies and was visible from Hawaii and Cuba in an apocalyptic display.

There was little electrical infrastructure at the time apart from the telegraph network. Currents induced by the space weather event surged along the wires and into offices across the globe. Operators felt electrical shocks and at least one was stunned unconscious. Some offices were set alight as sparks flew from the instruments. But the trains, running on steam, kept moving. These days, the same would unlikely be true – even the toilets on a train need electricity to work.

The next step is to take these findings and learn from industries that have experience mitigating the effects of space weather, such as the satellite industry and the power sector. Once vulnerabilities have been identified, appropriate levels of protection can be recommended. For example, a vulnerable piece of equipment that can be easily replaced and is only needed once a week will not need as much protection as a less critical but constantly used component.

The threat of space weather has crept up on us due to society’s increasing reliance on electronics. Now that this vulnerability has been identified, the job of boosting our resilience can begin in earnest. Then, we can return to viewing the aurora as one of nature’s treats, rather than a cause for concern.