One of the Doomsday scenarios that continues to fascinate is the possibility of the nation's electric grid being laid low by an electromagnetic pulse (EMP) or other attack.
In a House hearing last May, experts described the dire consequences that might result from a high-altitude nuclear detonation by a rogue power – North Korea was prominently mentioned, naturally. For example, Dr. Peter Pry from the Task Force on National & Homeland Security testified about an “existential threat”, with a 90% fatality rate through “starvation, disease, and societal collapse.”
For a more nuanced analysis, check out these articles written by a then-Harvard astrophysicist, which discusses the three types of electromagnetic pulses, E1, E2 and E3, caused by a nuclear burst at 25 – 35km altitude.
Each type has a different effect on electrical systems. An E1 pulse, the fastest, has a rise time in the nano-second range. It only lasts for a microsecond, but during that time can induce fields of up to 30kV/m at ground level. E1 affects primarily integrated circuits, and can damage relays, computer controls, and communications.
An E3 pulse is the lowest amplitude and has the lowest frequency, less than 1Hz. It can last up to 1,000 seconds, though, and poses the highest risk to the electrical grid since it can induce large currents even in buried cables. An E3 pulse can destroy HV and EHV transformers due to internal heating.
Unsurprisingly, publically-available real-world data is limited. One unclassified study of US Cold War test describes power outages in Hawaii after the Starfish series of high-altitude tests in 1962. Although no unambiguous electronic failures were noted, the sensitivity of current-day electronics is up to one million times greater than in the 1960s.
That hasn't stopped Hollywood. Systemic electrical grid failure is a popular plot element in post-apocalyptic TV shows. Take Revolution, in which weaponized “nanites” spread beyond their original target and permanently disable all electricity, not just the grid.
Following the event, the US splits up into six republics, whose members go about hacking each other up with knives, swords, spears, and so on. Hey, it's a TV show – write the science consultant, if you can find one. Or become one yourself. For the inside scoop on that option, go here.
But I digress. The relative amount of the three EMP lpulses is heavily dependent on yield, altitude, and other factors. Even apart from the technical difficulty, one drawback for a potential aggressor is that nuclear-powered EMP attacks are likely to leave identifiable clues such as a distinctive IR signature from the launch vehicle, inviting a massive retaliatory strike.
Terrorists are far more likely to employ easier, cheaper, and more readily-available methods such as explosives.
There's no doubt, though, that a large-scale failure of the electric grid would have serious, even fatal, consequences. The most likely cause of such a failure isn't to be found on Earth at all – it's a large solar flare followed by an extreme geomagnetic storm.
Ground currents induced during geomagnetic storms can melt the copper windings of transformers. Long power lines act like antennas, picking up the currents and spreading the problem over a wide area.
Geomagnetic storms are fairly common and correlate with the 11-year solar cycle. The most famous recent geomagnetic power outage occurred during a geomagnetic storm in March 1989 when six million customers in Quebec lost power for 9 hours. Since then, grids have become interconnected, allowing the coast-to-coast transmission of power but also exacerbating the effects of a similar event.
The geomagnetic storm of 1921 produced ground currents up to ten times stronger than the 1989 storm. Figure 1 shows the predicted loss of transformers per state from an event of similar magnitude today, with a 4800 nT/min exposure. More than 350 EHV (345 to 765 kV) transformers in the US would be at risk of permanent damage, leading to system collapse in the northwest and eastern regions of the country, and leaving 130 million without power.
The loss of electricity would cause water shortages, loss of perishable food and medications, disruption in sewage disposal, failure of telecommunications, and more.
The strongest geomagnetic storm on record occurred in August1859 during Solar Cycle 10 (1855 – 1867). Known as the Carrington Event, it wreaked havoc even with the technology of the day, shocking technicians and setting fire to telegraph papers.
The Carrington Event is estimated to be at least 50% more powerful than the storm of 1821; although systems such as radio and GPS would recover quickly, a repetition could have an economic impact of $2 trillion or more in the first twelve months.
Luckily, day-to-day threats to the electric grid tend to be more prosaic. Damage from terrestrial storms or trees are the two leading culprits, but the bronze medal position goes to squirrels, which cause around 12% of all electricity outages by shorting out equipment as they use poles and wires to go about their daily business foraging for nuts.
The squirrel problem is significant enough that many utility companies have installed squirrel deterrents including rotating baffles and bushings to cover sensitive points on the pole and transformer. See them in action in these “Mission Impassible” videos from CritterGuard.
As a weapon of mass destruction, squirrel-induced carnage may be lacking in the “Shock and Awe” department. But it does have the advantage of plausible deniability.