How damaging would a major solar flare induced EMP event really be?

Question

With specific attention to national electricity power grids.

Some pertinent details needed to answer the question might be.

1. What parts of the power grid get damaged by such an event
2. How do they get damaged
3. How quickly & easily can damaged components be replaced
4. What is the expected effect on nuclear power plants.

I suspect myself that other than potential meltdowns of the nuclear power stations this is probably all fixable in reasonably short order?

Here's a Quora answer to some of those questions, one of my first Google hits, I don't know how accurate it is but it ties into my suspicion it's a less than fall-of-government worldwide apocalypse scenario.

My own suspicion is it's likely the fried components can all be replaced within 12 months & aside from any loss of electricity production capacity from the loss of nuclear power plants to meltdowns when their monitoring & control systems got fried everything would be more-or-less back to normal by then.

Naturally I'd also expect a decade or more of increased brown-outs caused by the loss of any nuclear power plants that went into meltdown while replacements where built.

You just have to look at Chernobyl to know that a few nuclear power plant meltdowns aren't going to cause an apocalypse either, just provide us with a few really good nature reserves most poachers will be less than enthusiastic about going into.

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Howsoever, my own knowledge of the appropriate technical terminology to generate suitable search results in Google & elsewhere to confirm or disprove my hypothesis to my own satisfaction is it would seem sadly lacking, so I've come here for an answer.

Answer 1

The thing about solar flares is that they do not hit by surprise:

It usually takes days for the solar plasma ejecta to reach Earth. (Wikipedia, s.v. Solar flare)

Although the minimum time between a the emission of a solar flar and its arrival on Earth can sometimes be less than one day, nevertheless, there is time to prepare. And people around the world are actively looking for them, because the probability of a damaging solar flare hitting Earth is estimated at 12% per decade.

Note that as far as we know, the only solar flare of the size of the 1859 solar storm happened in 2012; it missed Earth by 9 days.

Moreover, the massive influx of plasma is preceded by a one-two punch of X-rays and fast charged particles; even if we somehow miss the flare, all communications satellites going offline would give a strong hint that the hammer is coming down.

Extreme solar storms pose a threat to all forms of high-technology. They begin with an explosion--a "solar flare"—in the magnetic canopy of a sunspot. X-rays and extreme UV radiation reach Earth at light speed, ionizing the upper layers of our atmosphere; side-effects of this "solar EMP" include radio blackouts and GPS navigation errors. Minutes to hours later, the energetic particles arrive. Moving only slightly slower than light itself, electrons and protons accelerated by the blast can electrify satellites and damage their electronics.

Then come the CMEs, billion-ton clouds of magnetized plasma that take a day or more to cross the Sun-Earth divide. Analysts believe that a direct hit by an extreme CME such as the one that missed Earth in July 2012 could cause widespread power blackouts, disabling everything that plugs into a wall socket. Most people wouldn't even be able to flush their toilet because urban water supplies largely rely on electric pumps. (NASA Science, "Near Miss: The Solar Superstorm of July 2012")

So, on to the questions.

1. What parts of the power grid get damaged by such an event?

   It depends. If the event came without warning then things are bad. But this is extremely unlikely. Under normal circumstances one can assume that in those parts of the world where the deleterious effects of a massive solar flare are to be expected the grid will be shut down in advance.

   Thus, the reasonable expectation is that the power grid won't be damaged. Although people will be warned to unplug their appliances, some won't. Expect a surge in demand for refrigerators, air conditioning units, television sets and laptop power sources; also, since some people won't disconnect their building distribution network from the grid, expect a surge in demand for the services of electricians.

   But let's say that due to the solar flare coinciding with an unexplained sudden epidemy of gross carelessness the grid is not shut down in advance. In this case, a solar flare of a size comparable with the one that produced the Carrington event in 1859 would induce large direct current voltages in any long unshielded electric cable in the affected part of the world.

   • The massive voltage spike, combined with the unexpected presence of DC voltage, would trip lots of of automatic breakers, breaking up the grid into small islands. In response to this, all power plants will enter emergency shut down. After an emergency shut down, nuclear power plants won't be able to restart for several days; gas and coal fired power plants may take several hours to restart, depending on how long the shut down period lasts.

   • More damaging, quite a few transformers may suffer damage, ranging from melted coils to spectacular explosions. Since the grid cannot be brought back until all substations are checked, this may make the duration of the black-out extend to one or two days.

   • It is also possible that quite a few generators will be damaged. Replacing them will take quite a while, since few shops keep hundred megawatt generators in stock.

   • Lots of electric appliances will be damaged. Expect large demands for refrigerators, air conditioning units, television sets and laptop power sources.

2. How do they get damaged?

   They get damaged by a sudden upsurge in voltage (combined with the most unexpected presence of large direct current voltage on alternating current lines), causing breakers to trip, laptop power sources to fry, small consumer electric motors to give up the ghost, etc. If the event hits and precautions are not taken, quite a lot of electric power infrastructure may be put out of service by the sudden voltage spike.

3. How quickly and easily can damaged components be replaced?

   Small appliances can be replaced quickly and easily. Residential grids can be checked and repaired relatively quickly. Large infrastructural equipment such as substation transformers and power generators will be painful to replace. We don't keep them in stock, and the manufacturers are not geared to make thousands of them in a short time.

4. What is the expected effect on nuclear power plants?

   This one is the easiest: solar flares are not expected to have any effect on power plants, other than causing their managers to shut them down. But, if the event hits in a week where all people on Earth are drunk (global Carnival?), the plants can suffer great damage to their geneators and to their connections to the grid.

   Once the event has passed and the grid is restored, hydroelectric power plants can resume producing power immediately, gas and coal fired thermoelectric plants can resume producing power in a few hours, and nuclear-powered thermoelectric plants can resume producing power in a few days. (Nuclear-powered thermoelectric plants do not like being shut down; they take their time to restart.)

   What this means is that in countries where nuclear power plants provide a large part of the electric energy production, grid service will have to be restarted gradually. Elsewhere, grid service can resume in a few hours after the even has passed.