A Cascading Blackout in Florida's Grid

The massive power outage that struck Florida today started when a nuclear power station shut down. Melissa Block talks to NPR's David Kestenbaum, who looks at the mechanics behind the nuclear power stations and the power grid in Florida.

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MELISSA BLOCK, host:

As we've said, the problems in Florida began with the failure of a substation that resulted in eight power plants shutting down or going offline.

NPR science correspondent David Kestenbaum joins me now.

And David, how is it that a problem at one electrical substation can cause such a massive outage every such a broad area?

DAVID KESTENBAUM: Well, as you know, the grid is very interconnected. That makes it stable and redundant. It allows you to send the power over long distances. But it also means that if the system is strained and you lose one part of it, you can get a cascade.

It's supposed to be built with some redundancy in, so that if one thing goes wrong, you really have to - it's supposed to be built so that you lose - you're supposed to have to lose two things in order for you to get a cascade.

My favorite description of the grid is actually of a room with heavy chandelier, filled with heavy chandeliers all attached to each other by one or two rubber bands, and that the rubber bands being the power lines. And that you can cut one or two, but if you're unlucky, you know, the whole thing sags or it starts oscillating, or you lose - you actually lose a chandelier. And here we lost a few chandeliers.

BLOCK: I've never thought of an electrical system quite that way. The nuclear plants that Greg Allen referred too there, why did that shut down?

KESTENBAUM: Turkey Point has two nuclear plants and they have power coming into them off the grid. And that's there for emergency situations. So, if something happened with the nuclear power plant, they would need to run, say, their cooling pumps in order to shut down safely.

So, if there's a problem with that power coming in, they're supposed to shut down immediately. And there was apparently an undercurrent. There's too little current coming in on that one of those lines for some period of time, and so the plants automatically shut down.

They're supposed to notify the Nuclear Regulatory Commission. The Nuclear Regulatory Commission told me they were notified in about 15 minutes (unintelligible), you know, was well within when they were supposed to be notified. And they said there were no problems.

In fact, it would have been a problem if the plant didn't shut down because that's what it was supposed to do.

BLOCK: So, it worked the way it was supposed to.

KESTENBAUM: It did.

BLOCK: David, you covered the huge blackout in the northeast in 2003. How does that one compared to what happened today?

KESTENBAUM: Well, that was the largest in American history was 15 million people. I remember, you know, we drove up to New York, and when we got there, just - I remember seeing a guy standing out in Manhattan with a candelabra. And that went on into the next day.

And that was, you know, that was announced. It started in Ohio and it cascaded up into Canada and all the way down, you know, into New York. So that was - this - by comparison, it was relatively contained and small scale. And they're hoping to get power back pretty quickly to everybody.

BLOCK: We've gone through chandeliers to candelabra. Let's see if we can fit one more light fixture into this. David, is there going to be an investigation into happened today in Florida?

KESTENBAUM: There will. I mean, they were - after that outage, there were standards that were made mandatory to ensure the reliability and instability of the grid. And those went into place sometime this past year. And so, there'll certainly be investigations to see whether everything that was done was supposed to be done.

For instance, the outage in 2003 started with some power lines that sagged and hit trees. So, one of the regulations is, well, you have to trim your trees. And so we don't quite know why this power station failed or exactly how far this thing should have spread, so it's hard to say exactly whether things happened as they were supposed to.

BLOCK: And the authorities in Florida are saying no safety concerns, right?

KESTENBAUM: No, not with the nuclear power plant. The - it shut itself down so there wouldn't be - I mean, there would have been a problem if it hadn't taken itself off. But it did.

BLOCK: Which it - okay.

NPR's David Kestenbaum, thanks so much.

KESTENBAUM: You're welcome.

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