Somebody attacked an electrical substation in California last year. This should make you concerned.

When we think about threats to America's energy infrastructure, we usually think about hackers. Hackers, or maybe, somebody taking a bomb to a nuclear power plant.

What we don't usually think about is some guys with guns.

According to a Wall Street Journal report by Rebecca Smith, last April a group of snipers cut the phone lines and internet access near a major electrical substation in San Jose, California, and then fired on the substation for 19 minutes, knocking out 17 transformers.

This is a big, big deal. The former chairman of the Federal Energy Regulatory Commission, Jon Wellinghoff, has been trying to draw attention to the little-discussed incident. Although the FBI doesn't think it was the work of a terrorist group, a retired VP of transmission for the utility company says that the attack was clearly well-organized and targeted at specific components of the substation. Although the utility, PG&E, called the attack the work of "vandals" in a press release, military experts told Wellinghoff that it looked more like a professional job. Now, Wellinghoff, and others, are worried that it could have been a dress rehearsal for a larger attack.

Why should you be worried about some people firing on a substation? Because the electric grid is a careful balancing act. A couple of years ago, I wrote a book about the creation of the grid, how it works, and how it affects our energy options today. One of the key things I learned is that electricity must be actively managed, 24 hours a day, 7 days a week. There are always people working to make sure that electric supply — the amount of electricity being produced by power plants — is essentially equal to electric demand — what you and I and the rest of the country are using at any given moment. If that balance gets out of whack, even by fractions of a percent, it creates instabilities in a fragile system that can lead to blackouts.

When this substation, which serves Silicon Valley, went offline, electricity had to be rerouted from other places, to keep the tech industry working. The attack happened between 1:30 and 2:00 in the morning, when electricity demand is extremely low. If it had happened in the middle of the afternoon — the peak in electricity demand — that rerouting would have put a lot more strain on the system. And there's a risk that it could have created a blackout that spread to other places, far from the original substation.

Back in 2012, I explained here at BoingBoing how seemingly local events can become massive blackouts. That very thing happened in 2003, when most of the East Coast lost power.

I like to say that the grid is a lot like a lazy river at a waterpark. It’s not a line, it’s a loop—power plants connected to customers and back to power plants again. And like the lazy river, it has to operate within certain parameters. The electricity has to move at a constant speed (an analogy for what the engineers call frequency) and it has to flow at a constant depth (analogous to voltage). In order to maintain that constant speed and constant depth, you have to also maintain an almost perfect balance between supply and demand … everywhere, at all times. So when one generator goes out, the electricity it was supplying has to come from someplace else. Like a stream flowing into a new channel, the load will shift from one group of transmission lines to another.

But, the more electricity you run along a power line, the hotter the power line gets. And the hotter it gets, the more it droops, like a basset hound in a heat wave. If nearby trees aren’t trimmed, the lines can slump too close to the branches—which creates a short circuit. When that happens, the loads have to shift again. All of this disrupts the speed and the depth on the river of electrons. The more lines you lose, the more likely it is that the remaining lines will, themselves, droop into something. The more lines that short, the more power plants have to shut down to protect themselves from fluctuations in frequency and voltage. The more times you have to shift load around, the more the grid starts to get away from you. In 2003, six transmission lines went down in a row, several of them major channels for the flow of electricity. Those losses were what turned a small series of mistakes into a catastrophe.

If somebody took out the right combination of substations, all at the same time, they could trigger a huge blackout, simply by stressing the grid too much as it tried to reroute itself around the outage. And that would be relatively easy because most substations have very little security. A chainlink fence. A couple of security cameras. That's about it.

Edit: My first draft of this made it sound like the solution, the only solution, would be to hyper-securitize all the substations in the US. Frankly, that's pretty much impossible. Instead, this should be another reminder that we need to be upgrading our electric grid. We need storage. We need smart grid technologies that enable us to more easily react to disruptions. We need microgrids that allow parts of the grid to function separate from the rest. These are same technologies and upgrades that we need to deal with the threat of unpredictable weather. And the same ones we need to allow us to build more renewable energy into the grid. The potential risk of direct, intentional attacks on the grid is just one more reason to be concerned about a decaying infrastructure that hasn't seen serious upgrades since the 1970s.

Meanwhile, no suspects have ever been identified in the April 2013 attack.

Image: South Prarie substation, a Creative Commons Attribution (2.0) image from vax-o-matic's photostream