How the U.S. Power Grid Is Like a Big Pile of Sand

And why that puts the country at risk for widespread power outages.

National Journal
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Marina Koren
April 8, 2014, 7:27 a.m.

Last month, The Wall Street Journ­al gave us quite a scare.

“The U.S. could suf­fer a coast-to-coast black­out if saboteurs knocked out just nine of the coun­try’s 55,000 elec­tric-trans­mis­sion sub­sta­tions on a scorch­ing sum­mer day,” Re­becca Smith wrote.

It’s no secret that North Amer­ica’s three massive power grids, the in­ter­con­nec­ted sys­tems that trans­mit elec­tri­city from power plants to con­sumers, are not in­vin­cible. The U.S. power grid is, in fact, big enough to fail.

In oth­er words, the grid may be not be the “right” size — big enough to dis­trib­ute power ef­fi­ciently, but small enough to pre­vent wide­spread black­outs, such as the 2003 black­out that cut power to 50 mil­lion people in the U.S. and Canada for two days. So, break­ing up the sys­tem in­to smal­ler grids could re­duce the like­li­hood of power out­ages, ac­cord­ing to a new study in the journ­al Chaos, pub­lished by the Amer­ic­an In­sti­tute of Phys­ics.

The re­search­ers — Dav­id New­man, a Uni­versity of Alaska phys­i­cist; and Ben­jamin Car­reras, a phys­i­cist at a Ten­ness­ee-based con­sult­ing com­pany — ana­lyzed how the west­ern U.S. grid, one of the big three, re­sponds to vir­tu­al out­ages. The sys­tem has more than 16,000 nodes, in­clud­ing gen­er­at­ors, sub­sta­tions, and trans­formers.

“We found that for the best trade-off between provid­ing backup power and black­out risk, the op­tim­al size was 500 to 700 nodes,” New­man said. The big­ger the grid gets, the great­er the risk of fail­ures.

Need help visu­al­iz­ing the prob­lem? Just think of a sand­pile, New­man says.

“Sand­piles are stable un­til you get to a cer­tain height. Then you add one more grain and the whole thing starts to ava­lanche,” New­man said. “This is be­cause the pile’s grains are already close to the crit­ic­al angle where they will start rolling down the pile. All it takes is one grain to trig­ger a cas­cade.”

That one grain could very well be, like Smith sug­ges­ted, some kind of co­ordin­ated at­tack. Or it could be something as in­no­cent as a hot sum­mer day that makes us crank up the air con­di­tion­ing.


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