Expert: Why wasn't blackout isolated?
(CNN) -- The head of the North American Electric Reliability Council said it appeared that the failure of three transmission lines in Ohio triggered last week's power blackout that spread to Michigan, Canada and New York.
NERC's Michehl R. Gent said Saturday he was "fairly certain at this time that the disturbance started in Ohio. We are now trying to determine why this situation was not brought under control after the first three transmission lines relayed out of service. We will get to the bottom of this."
CNN's Sean Callebs spoke Sunday to the founder of howstuffworks.com -- Marshall Brain -- to explain how a cross-country electrical power grid works and what might cause one to fail.
CALLEBS: Let's talk about how a grid works. I wonder how many people realize that a grid can't store electricity. Power must be used as it comes down the line.
BRAIN: That's exactly right. So you have millions of people demanding electricity and you have dozens of power plants supplying that electricity. And it all has to be perfectly matched every second. And if something goes down and that match gets out of whack, then you can have a problem -- like we saw last week.
CALLEBS: OK. Tell us, basically as you understand it, what happened. We saw this in California a couple of years ago. It apparently was like a domino effect here in the Midwest and in the Northeast.
BRAIN: Right. So in '96, the California crisis was caused when something really simple, the power lines sagged into some trees and just shorted, just like a lightning strike or something to ground. So right now the thought is that three transmission lines went out simultaneously.
And you can imagine the designers were thinking, "OK, we can imagine one going out. We can imagine two going out. But three will never go out." And it just -- you know, something lined up so that all three went out.
And then all their load transferred out to other neighboring lines and then they failed. And the question will be why wasn't it isolated to a cell? You know, to one state or something? How did it spread so far?
And that will probably be because something else might have failed on a smaller basis or maybe some stuff was off line for maintenance.
CALLEBS: But what about this argument the alarms didn't work? I mean, to some, it may sound like "the dog ate my homework."
BRAIN: Well, a lot of times it can happen so quickly. Like I've heard reports that this whole thing, the whole region went dark in nine seconds because of that cascading overload. It may be that there's a need to look at the cellular design of the grid and beef up the capacity so that there is an ability for the alarms to react and actually isolate states or regions more quickly. They don't take months to figure out that. But it will be a design issue like that, where there wasn't an easy way to break or fire-wall off that region.
CALLEBS: You know, it was hot, but it wasn't scorching for a prolonged period of time. Why did it happen so quickly to such a broad area?
BRAIN: Well, we won't know for months, but it could be that -- for example -- three plants were off line for maintenance -- and it was scheduled -- and it was all completely normal, or some transmission pieces were off line at that same time.
And it's just that it was such a big failure, who would have thought that three things would fail simultaneously. So that, in combination with normal maintenance, probably is what caused it to spread so quickly on that particular day.