Celestial Shooting Gallery, Part Three: When a CME Hits the Atmosphere

by Garry R. Osgood on June 15, 2013

in Disasters, Emergency Power Systems, Energy, Grids & Networks, Infrastructure, Planning and Preparedness

Failed GSU transformer at Salem River, NJ

A Generator Step Up (GSU) transformer failed at the Salem River Nuclear Plant during the March 1989 geomagnetic storm. The unit is depicted on the left; some of the burned 22kV primary windings are shown on the right. Though immersed in cooling oil, the windings became hot enough to melt copper, at about 2000 degrees F. John Kappenman, Metatech

Coronal Mass Ejections are mainly charged particles, protons and electrons. When a CME arrives at Earth, the charged protons and electrons come under the influence of the Earth’s own magnetic field, the magnetosphere. Charged particles spin around the lines of magnetic force that comprise the magnetosphere, which diverts most of CME harmlessly around the planet, keeping Earth’s surface tranquil.

If the ejection is large enough, however, it can distort the shape of the magnetosphere, occasionally causing magnetic flux lines to snap and reconnect. When this happens, charged particles leak in and follow the magnetosphere’s flux lines down to the Earth’s ionosphere. There, they strike oxygen and nitrogen molecules and strip them of electrons. These ionized gases glow, giving rise to the ethereal beauty of the auroras around the north and south poles. Unfortunately, these excess charged particles also produce immense electrojets.

Typically millions of amperes in magnitude, these currents of ionized particles vary in both position and magnitude, and as they flow chaotically through the ionosphere, they establish around themselves constantly fluctuating magnetic fields, which, in turn, inductively couple with electrical transmission lines. Upward to a thousand miles long, these transmission lines act like secondary coils of an immense transformer and their coupling with the magnetic fields that surround the electrojets  give rise to geomagnetically induced currents (GICs). These currents surge along electrical transmission lines and force transformers off their sweet spots.

If the bias current is sufficiently large and endures for minutes or hours, then the affected transformers experience half cycle saturation. That is, the alternating current, now riding on top of a large geomagnetically induced current, saturates the transformer on every other cycle, when the two currents reinforce each other. When a transformer core saturates, there are not enough magnetic flux lines to convey energy from primary to secondary coils. The excess energy heats the iron core instead. If the transformer cannot dissipate the excess heat fast enough, it can burn up, meltdown or explode. It’s not a big deal if one or two go, but a dozen transformers blowing up over a wide area in a short period of time can bring down the whole grid.

The most chilling aspect of a grid collapse is its far-reaching scope. When Katrina wiped out New Orleans, there was still a functioning infrastructure in the rest of the country from which aid could be dispatched. But a nationwide collapse of the power grid would impact everywhere, all at once, engaging every first responder available to deal with the local crises.

Then there are spin-off disasters. Within hours after the grid drops, food and medicines begin perishing (no refrigeration), fresh water supplies dwindle (no pumping stations), raw sewage mounts (no filtration systems), personal communications fail (batteries exhausted in cell phones, tablets and laptops). It will get very dark at night, even in urban areas. Toughs will take over the streets. Vigilantes will take government into their own hands. While, over the short haul, critical infrastructure could be supplied by emergency generators, these almost always run on refined hydrocarbons and if the national grid goes wholly down, refinery capacity would be lost and fuel stockpiles would soon deplete. It could get very, very ugly and stay that way for a long time.

The difficulty with rapid recovery lies with the ubiquitous transformer, especially those involved in bulk transmission over long distance trunk lines. These multi-ton devices usually cannot be repaired in the field. Often hand-crafted for a particular locale, they usually require manufacturing lead times of 12 months or more. These estimates presume that, somewhere on the planet, functional infrastructure with appropriate technology is available, but if electrical grid failures are widespread, with Asian and European grid systems compromised as well, then lead times may be significantly longer. Nor is it especially easy to identify and per-emptively remediate suspect transformers. Because they have custom designs, such transformers can contain numerous subtle design variations that complicate the calculation on how they might survive a geomagnetic storm. The ability to assess existing transformer vulnerability or even to design new transformers that can tolerate saturated operation is not readily achievable.

Of course, it is not like everyone is just sitting around waiting for some coronal mass to eject. Gerry Cauley, president of the North American Electric Reliability Corporation (NERC), suggests that paranoia may very well be the first problem to attack: “I am concerned that overstating the issue through hyperbole and trying to motivate action with a picture of solar disturbances causing instant devastation and the ruination of the modern world does not provide a rational catalyst for decision‐making or help prioritize actions, I believe the physical challenges are real but there are practical solutions available.” NERC was empowered in 2006 to serve as a central regulating authority among the five hundred companies that generate or transmit power in the North American distribution grid; it strives to facilitate communication and develop protocols necessary for a stable grid, even one in the midsts of the Perfect Geomagnetic Storm.

So, to quote Douglas Adams: Don’t panic. Put fresh towels in your go bag and buy portable solar panels, as these can charge all kinds of small electronics. But on a larger scale, Cauley’s “practical solutions” are not, by themselves, solutions. The technologies which Cauley would like to transform into practical solutions depend on supporting policy, cooperation across national boundaries,  adequate budgets and seasoned management. Unfortunately, in this era of sequestered budget lines, one wonders how well funded are many of the Federal agencies with key roles in heading off ‘The Katrina of Space Weather.’

The next post in this series will take up the issue of preparedness, or the lack thereof, and what, if anything, our readers can do about it. In the meantime, don’t forget your towels.

Previous – Celestial Shooting Gallery, Part Two: The Physics of Geomagnetic Storms

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