Blackout: What's wrong with the American grid

It began with a few small mistakes.

Around 12:15, on the afternoon of August 14, 2003, a software program that helps monitor how well the electric grid is working in the American Midwest shut itself down after after it started getting incorrect input data. The problem was quickly fixed. But nobody turned the program back on again.

A little over an hour later, one of the six coal-fired generators at the Eastlake Power Plant in Ohio shut down. An hour after that, the alarm and monitoring system in the control room of one of the nation’s largest electric conglomerates failed. It, too, was left turned off.

Those three unrelated things—two faulty monitoring programs and one generator outage—weren’t catastrophic, in and of themselves. But they would eventually help create one of the most widespread blackouts in history. By 4:15 pm, 256 power plants were offline and 55 million people in eight states and Canada were in the dark. The Northeast Blackout of 2003 ended up costing us between $4 billion and $10 billion. That’s “billion”, with a “B”.

But this is about more than mere bad luck. The real causes of the 2003 blackout were fixable problems, and the good news is that, since then, we’ve made great strides in fixing them. The bad news, say some grid experts, is that we’re still not doing a great job of preparing our electric infrastructure for the future.

Let’s get one thing out of the way right up front: The North American electric grid is not one bad day away from the kind of catastrophic failures we saw in India this week. I’ve heard a lot of people speculating on this, but the folks who know the grid say that, while such a huge blackout is theoretically possible, it is also extremely unlikely. As Clark Gellings, a fellow at the Electric Power Research Institute put it, “An engineer will never say never,” but you should definitely not assume anything resembling an imminent threat at that scale. Remember, the blackouts this week cut power to half of all Indian electricity customers. Even the 2003 blackout—the largest blackout in North America ever—only affected about 15% of Americans.

We don’t know yet what, exactly, caused the Indian blackouts, but there are several key differences between their grid and our grid. India’s electricity is only weakly tied to the people who use it, Gellings told me. Most of the power plants are in the far north. Most of the population is in the far south. The power lines linking the two are neither robust nor numerous. That’s not a problem we have in North America.

Likewise, India has considerably more demand for electricity than it has supply. Even on a good day, there’s not enough electricity for all the people who want it, said Jeff Dagle, an engineer with the Pacific Northwest National Laboratory’s Advanced Power and Energy Systems research group. “They’re pushing their system much harder, to its limits,” he said. “If they have a problem, there’s less cushion to absorb it. Our system has rules that prevent us from dipping into our electric reserves on a day-to-day basis. So we have reserve power for emergencies.”

None of this means the North American grid is a perfect, or even an ideal, system. The electric grids that exist today evolved, they weren’t designed by anybody. Every electric grid on Earth is flawed, but they’re all flawed in different ways. So we can talk about serious problems with the North American grid—but that doesn’t mean that you should be stocking up on home generators and canned peas in preparation for an India-like event. The scale is different, and the problems are different, too.

All the Small Things

So what did cause the 2003 blackout? There were a couple key issues, but at least one is likely to surprise you. First Energy, the conglomerate that owned both the broken generator and the failed alarm system, had also been lax on trimming trees near their power lines. It’s an amazingly simple, non-techy, problem, but it mattered.

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.

A Failure to Communicate

Even more important than the untrimmed trees, though, was the lack of communication.

The North American electric grid is a patchwork quilt, not a single entity. It’s made up of chunks controlled by different—and often competing—utility companies. Those chunks are aggregated into management districts. In the case of the Eastern part of the continent, all of the management districts are aggregated into a larger joint district. There are a lot of hands working to make sure the grid operates the way it should. But those hands don’t always know what the others are doing, at least not fast enough.

The issue is something that grid experts call situational awareness—basically, the big picture. In 2003, the people trying to stop the blackout didn’t have a clear view of it. Partly, that had to do with the faulty software program that wasn’t turned back on and the alarm system failure that apparently went unnoticed. But it was also just how the grid worked. The systems in place to tell grid controllers what the electrons were doing moved a lot more slowly than the electrons themselves.

In 2003, it took about 30 seconds for data about what was happening on the grid to be gathered, compiled, analyzed, and displayed in a way that grid controllers could use. That sounds pretty fast, until you consider the fact that changes on the grid happen much, much faster***. If a power plant goes offline in Arizona, it can create a measurable effect in Canada in about a second. If your view of the grid is updated only every 30 seconds, you miss important details. After the 2003 blackout, grid experts went back and essentially replayed the whole thing in a computer modeling program. The idea was to try to get a better idea of where things went wrong and how a similar event could be prevented in the future. They found that, about an hour before the blackout, the grid was showing signs of stress that controllers didn’t see at the time, said Carl Imhoff, manager of the Energy and Environment Sector at PNNL. It wasn’t the controllers’ fault. They simply didn’t have the technology to see the big picture.

Fixing the Grid

Today, that technology exists. Phasor Measurement Units are kind of the opposite of sexy. Also known as PMUs, they’re just anonymous little boxes that sit on server racks in electrical substations. But phasors are linked into transmission lines. They see what’s happening on the line—how well supply and demand are balanced, whether voltage and frequency are stable and within the normal range. That’s just one point of data, recorded in one place. But a network of phasors can tell you a lot. It can show you, for instance, if the stability of the grid is changing as electricity moves from Cleveland to Columbus. And the phasors process that information far more quickly. Today, our grid can give controllers information about the big picture in less than 10 seconds. Researchers like Massoud Amin are working on getting that response time down to fewer than 3 seconds.

If we’d had a phasor network in 2003, grid controllers would have had that hour warning about the problem. There’s a good chance they’d have been able to fix it, or, at least, make the resulting blackout smaller and more localized.

When it comes to PMUs, 2003 was really a wake-up call. It led utilities and the government to team up to install a true phasor network throughout the United States. That effort is currently ongoing. In 2009 there were maybe 200 phasors in operation. By the end of 2013, there will be more than 1000 installed throughout this country. Over the last five years a partnership between federal Recovery Act funds and private industry dollars has invested $7.8 billion in upgrading the grid, Massoud Amin said.

The problem, he added, is that this isn’t nearly enough.

Our grid is old. The average substation transformer is 42 years old—two years older than the designed lifespan of a substation transformer. For the most part, our grid hasn’t been modernized—it’s largely mechanical equipment operating a digital world, Clark Gellings said. Perhaps most importantly, the grid isn’t being prepared for the future.

”From 1995-2000, the electricity sector put less than ⅓ of 1% of net sales into research and development,” Massoud Amin said. “In the following six years, that number dropped to less than 2/10 of 1%. We are harvesting the existing infrastructure more and investing less and less in the future.”

Phasor networks are a success story in the making. So are new national rules Gellings told me about, which put a much higher penalty on utility companies that don’t keep their trees trimmed. One untrimmed tree can cost $1 million in fines. All of this will help prevent blackouts of the size we had in 2003. But it doesn’t help deal with what’s coming 20-30 years down the road.

It’s not just that the infrastructure itself will eventually age out. Where we get electricity from, who uses it, and how much we use is all changing. In the future, we’re going to have more electricity production happening in the rural Midwest, where wind resources are most abundant, but the people will still live far away. We keep using more electricity, in general, and we’re more dependent on it now. We’re only going to become more dependent in the future. Jeff Dagle told me that improvements are being made, but they might not be moving fast enough if there’s a major change in energy use—for instance, if Americans start buying electric cars at higher rates than they do today.

The frustrating thing is that this isn’t simply a technology problem. It’s also social and political. Just like the national grid is really a patchwork of grids, it’s also a patchwork of regulatory systems. That uncoordinated mixture of regulation and de-regulation often fails to incentivize the investments the grid actually needs. Building transmission lines, for instance, is a job that crosses multiple states. Many of those states aren’t going to get a direct benefit from the line, even if that’s what’s best on the whole. Local regulators may understand that, but when they have to operate in the best interests of their state or county, they might still challenge the line, Gellings said. This is part of why it can take as long as 12 years to get a single new transmission line built. In another example, de-regulation in many states has created a confused system where there are now lots of stakeholders in the electric grid, but nobody has an incentive to think about, or invest in, the long term.

If we want the grid to work as well three decades from now as it does today, we need to put some money into it. Massoud Amin has estimated the cost of grid improvements. To make the grid stronger—adding more high-voltage lines and upgrading the existing ones—he says we need to spend about $8 billion a year for 10 years. To make the grid smarter—digital, centralized, automated, and with the kind of big-picture communication that helps us stop blackouts before they happen—it’ll take an investment of $17-20 billion a year for 20 years.

That sounds like a lot of money. That sounds completely undoable. And maybe it is. But Amin says you have to think about what you’re saving, as well. Remember how much the 2003 blackout cost us? Most blackouts that happen aren’t that big. They’re local things, that happen to your neighborhood, or your town, or your county. But they happen a lot. Depending on what part of the United States you live in, the grid averages 90-214 minutes of blackout time per customer, per year*. And that’s not even counting the blackouts that happen because of extreme weather or other disasters, like fires. All that downtime adds up. Amin says the average cost is more than $100 billion per year.

And that’s the difference between an expense and an investment. Over time, the investment pays for itself.**

*Japan, in contrast, averages 4 minutes of interrupted service per customer, per year.

**Massoud Amin estimates that these investments would save $49 billion a year that would otherwise be lost due to blackouts. The improvements would also make our grid more energy efficient, which he says could save an additional $20 billion annually in energy costs. You can read more about this in the reports he’s written about his research.

Learn about how the grid works and what grid controllers do by reading a free chapter from my book, Before the Lights Go Out.
Read the full report on the 2003 blackout

***The original version of this story stated that electrons moved at almost the speed of light. This is a misunderstanding on my part. I've changed the wording to reflect what's really going on.

Image: Untitled | Flickr - Photo Sharing!, a Creative Commons Attribution Share-Alike (2.0) image from krunkwerke's photostream


  1. On the upside, being in Toronto during that blackout was one of the most surreal and wonderful experiences of my life. We scavenged wood from alleyways and cooked chicken in the parking lot behind our building. We had dance parties in the streets and aboard stalled street cars, under a starry sky that we never get see anymore. 

    1. shops were giving away ice cream, and patio beer parties everywhere.

      Shame I had to walk most of the way home since the streets were jammed, it was amazing how many people volunteered to be impromptu traffic wardens.

      Cell phones all worked, though busy.

  2. While actual cause of the North Indian blackout is still under investigation (the leading cause is over-drawing from certain States), I’d like to point out a few  factual errors here. 

    1. India’s grid is sub-divided into Northern, North Eastern, Eastern, Western and Southern grids. There’s no one national grid as such where power goes from Kashmir to Kanniyakumari. The Southern grid is not synchronous with the other four grids but is connected. This week’s blackout saw only the Northern, North Eastern and Eastern grids fail.

    2. The majority of India’s population is in fact, in the “North”, specifically in the states in which the grids failed. More power plants are actually in the East where the coal is abundant and a few along the major rivers, higher up in the Himalayas. See this map for list of thermal power plants (which form the bulk of India’s electricity output)

    3. As of 2011, the five states with the largest demand were mostly in the South and West (2 in the South and 2 in the West) and only 1 was in the North Four out of the five biggest electricity consuming states were actually not affected by the blackout last week. These four states are also among India’s most industrialized.

    1. United States’ power grid is also subdivided as well.  There are only three regions though – East, West and Texas.  (Yeah Texas has its own).  The three aren’t synchronous either. I know Texas has built some interconnects with the western grid and with some of the Mexican grid if ever necessary.

  3. “90-214 minutes of blackout time per customer, per year”
    That’s appalling.

    I’m curious as to what the stats are for the UK, because maybe I’ve been exceptionally lucky, but I haven’t experienced a power-cut at home (excluding lights flickering) since I was a kid, I think January 1990.

    We had a couple at work, but that was due to people digging up the road cutting through the wrong cable, which has nothing to do with the resilience of the system

    1.  As far as I know, The UK’s electrical grid, like Japan’s is one of the best. According to the latest grid figures less than a thousand kW/hours were dropped over the whole system last year.

      Of course, the UK has a number of things in its favour A small, compact island means that generation is never too far from supply. A grid that was designed as a single entity, back in the days when power was nationalised.and an absolutely insane amount of peaking capacity, put in place because of the regular stress tests run on the system as the entire nation puts the kettle on during ad breaks.

    2. In my experience in Canada (living in two reasonably big cities with what I assume are fairly modern grids), 90 minutes of power outage a year is probably a reasonable guess.  I suspect rural customers would experience longer delays in repairs to their power lines.

      Almost all of the outages were during storms with heavy winds.  In pretty much every neighbourhood where I’ve lived, the power lines have been above ground, and the trees much taller than the power poles, so it’s not surprising when power goes out in a storm.

      As you note though – 90 minutes’ outage to the average residential customer, in outages that typically cover only a few city blocks, is very different from 90 minutes’ outage to a whole city or region.

    3. Growing up in Massachusetts, we had a blackout pretty much every afternoon in the summer, when the thunderstorm broke. In Southern California, outages seem more likely to be from traffic or digging accidents. I was out for two hours a couple of weeks ago. And we’ve had a planned eight-hour loss of service almost annually.

  4. That sounds pretty fast, until you consider the fact that electrons move at close to the speed of light.

    Maggie, this is actually not true at all.  From wikipedia electric current article:

    Typically, electric charges in solids flow slowly. For example, in a copper wire of cross-section 0.5 mm2, carrying a current of 5 A, the drift velocity of the electrons is on the order of a millimetre per second.

    Electrons move through wires slower than most people walk.  What moves at the speed of light is changes in the electric field.

    Otherwise, great post.

    1. Drift velocity is not instantaneous velocity. The RMS voltage of that copper wire is 120V, meaning a peak voltage of ~170V. At 170V, an individual electron would be moving at over 7 million m/s, about 2-3% of the speed of light. On a 10kV distribution line you’re at ~20% the speed of light, or 60% for a 100kV transmission line.

      I’m a physics guy, not an electrical engineer, so I don’t have a firm grasp of whether this number or drift velocity is the relevant one for grid performance. But on first principles it looks to me like Maggie is not wrong, just referring to something different.. 

      1. I’m not sure about your interpretation there.  I think Maggie’s talking about electrons actually physically moving through the wires from one spot to another.
        1. This is not directly relevant to electricity transmission; the only part relevant to that is the change in the electric field.
        2. Instantaneous velocity is not relevant to the speed at which electrons actually, physically move through wires; drift velocity is. For similar reasons, we do not determine the speed a car is moving by figuring out how fast its molecules are vibrating.
        Also a physics guy, not an electrical engineer, but from what I understand neither the drift velocity nor the instantaneous velocity is relevant, just the changes in the electric field.

        1. Surely Maggie can clarify herself.

          But it seems to me that for the purposes of her article, the salient point is how quickly the effects of a disturbance at point A are transmitted to point B.

          In that scenario, the movement of actual electrons isn’t nearly as important as the change in electrical potential.

          That said, it does seem that the article’s wording clearly discusses the actual velocity of electrons. That may not be what Maggie meant to discuss, but surely from a pedantic point of view (and pedantry in science is highly useful) your original comment was accurate.

          1. Hey guys, 

            I haven’t been able to verify the electron thing with my sources, as they’re all off for the weekend. But it sounds as though I’m getting something confused here, so I’ve changed the wording in away that side-steps electrons and just talks about how quickly changes happen on the grid. The change is noted in the story with “***”. Thanks for catching this. 

  5. While most of the Northeastern US lost power in the 2003 blackout, our home (located in Northeast Ohio) never lost power. I have no idea how or why our portion of the grid did not go down. The odd thing is that our block of homes oftentimes does lose power every now and again while the rest of our neighbors do not. Go figure.

  6. It’s frustrating to me how all of this infrastructure is invisible and only handled by experts far away from me. With air traffic control we have some idea at least what it might be like, but no one has made a movie yet AFAIK about power balancing.

    If appliances could be controlled through the same wire that powers them, we could evolve a more robust way of prioritizing power demands. Kind of like the ‘niceness’ flag in unix software that determines how much CPU time each job should get.

  7. Domestic infrastructure including the grids, bridges, locks and dams, roads, public schools, public transportation, are all suffering under the impossible weight of our military budget. The notion that 20 billion a year is impossible to attain for the corrections and improvements needed in the grid is directly tied to the political reality that until military spending is drastically reduced any and all major domestic infrastructure overhauls are fiscally impossible. We are a nation of citizens held to the narrow confines of goals inherent in our ( their ) military-industrial complex . These include a militarized domestic police force, a vast domestic intelligence gathering operation, Northcom and so much more; all to the tune of hundreds of billions of taxpayer dollars. To write about and discuss energy and infrastructure and domestic funding without at least a mention of our nascent police state and overextended military foreign policy is to in effect discuss the details of the broken table that the dead elephant is laying on without mentioning the elephant. Science is political because the goals of scientific institutions are primarily guided by funding and profit for corporations over the needs of civility and humanity.  I dont think its the responsibility of scientist to make complex political statements in connection to their practice but given the starkness of the economic priorities of today, taking note of the imbalance is stating basic and objective facts. This is where the truth becomes unspeakable if you want published and you want accolades without being marginalized as controversial. Below is an excellent breakdown of where the federal tax money goes in this country. Now see where 20 billion might be freed up.

  8. $30 billion a year sounds like a lot of money, but it’s not. There are a third of a billion of us. $30 billion a year is less than $100 per person per year, less than $8 a month per person living in the house if we added it to everybody’s electric bill. Except that, in practice, it’s half that, because more than half of our electrical consumption is commercial and industrial.

    (It can quite fairly be pointed out that if you added that much to companies’ electrical bills, they’d pass it along in the product costs, so if you want to use the $8/month figure, I won’t object. But that’s not the number people would actually see, they’d see $4/month or less plus a tiny, tiny uptick in the inflation rate.)

    Against the lights going out and staying out? Against America eventually having the kind of electrical grid problems that post-war Iraq experienced? We ought to just suck it up and pay it.

  9. In 2003, I was working in an old garment factory building that had been converted into an open, spacious office environment. Nice, if a little run down and patchwork. In particular, the power was sometimes…odd. 60V potential between the grounds of different circuits, things like that, but mostly if you just plugged something in, it worked.

    The lights on my floor were entirely run by one light switch. This means that the switch actually flipped a relay by the breaker box, and the relay could handle the current necessary to run the lights. My desk was in a cluster of four, along with my boss and two coworkers on my team, and our cluster was right next to the fuse box.

    On the morning of August 14th, the relay, enclosed in a metal box, started buzzing. It stopped, then started again, louder. My boss walked over to the wall with the fuse box and relay, said “What’s wrong with this damned thing now?” and smacked the relay box with his fist.

    At that exact moment the lights went out, and didn’t come on. The look on his face was priceless – “Oh, man, what did I do?” Except it wasn’t just the lights, it was the computers, too. Minutes passed, and nothing came back on. We looked out the window – the street lights were out! Every building was out, from both local providers!

    More time passed, and we got a few phone calls and slowly pieced together that the entire eastern seaboard was down. By that time, it was pretty clear that the blackout wasn’t caused by smacking a relay on the wall. But for that one brief moment, before reason kicked in, it was a heady thought!

    It was only much later that we learned it was from overburdened lines arcing to trees, at which point smacking the relay didn’t feel quite so far of as we’d figured.

    1. How large a flash would one need to illuminate those buildings? I saw someone just last night taking pictures of a sunset where the foreground mountains were 30 miles away – with his on-camera flash blasting away. I suspect someone standing on a hillside looking back would never see that flash go off…

      Cropping/framing would have been more easily done. Unless the point is to contrast the unlit foreground with the extravagantly-lit skyline…

  10. I did research about this. It wasn’t that the monitor program didn’t get restarted, it couldn’t be restarted— the bug continued to gum things up.

  11. I don’t think syncrophasors would have solved the problem, First Energy was blind because their state estimator went down and couldn’t be brought back online while their operator displays/SCADA hung up and showed them the same data for several hours. They had neighbouring operating centres telling them that their data was wrong, based on load flows, but they didn’t believe them.

    That said, syncrophasors are cool, you used to be able to go on the Schweitzer (SEL – big proponent of syncrophasors) website and see the various grids (East, West, ERCOT) spin around a bit out of sync with each other.

  12. Hey Maggie- I appreciate all of these articles on energy- incredibly important info for us all. One thing I can’t get a clear answer for- alternative energy. One of the biggest things people can do to help all our greenhouse issues is to switch energy suppliers from the default (ConEd for us New Yorkers) to a “greener” supplier that generates power via wind or hydro (though hydro has its own issues.) It takes a minute to do and costs only slightly more. I’ve heard people express skepticism that this is really doing anything due to the grid’s infrastructure, but I can’t really find more specific criticism than that. It seems simple- the more people that switch to green suppliers, the less we are paying out the coal / nuclear suppliers. Suppliers notice the demand increases, and follow that trend. Eventually, coal-based energy is a thing of the past. Obviously, there would be other issues if the country were to shift like that, but my point is, is the basic theory sound? Does the grid work in such a way that contradicts this theory? Future blog post idea… or  comments open to anyone’s expertise!

  13. what about a sort of crowdsourced grid.  Many points of generation, many points of storage, distribution is more a matter of redistribution of surplus’…its seems that aside from intial investments, it addresse the resiliency issue, and does not require discarding the current system, more of a sort of retrofit.  

    the notion is decentralization

    1. Something like this may be coming as people embrace Solar and Wind power, but generally in most areas the problem is ‘not in my back yard’ – people don’t want the power company telling them to build solar panels on their house.. However as the cost of that technology comes down (and the grid might get more unreliable) it might become more fesible

  14. $20 billion a year for 20 years?  That’s actually chump change when you consider that between September 2008 and February 2009, we pissed away four times as much on a valueless “bank bailout” and an almost equally valueless “stimulus”.

    1. You may want to read this story more closely. The stimulus (aka the Recovery Act) is a key part of why any major improvements are happening on the grid at all. It’s not enough, but at least its something. 

  15. In a story about America’s power grid, what’s with the Toronto skyline??
    What happened to all the pictures of, say Chicago, ferinstance. 

  16. A bit more detail on the 2003 blackout:

    1. So the first thing that happened was that higher than expected temperatures led to higher load than anticipated in day-ahead trading on the Midwest ISO – specifically in northern Ohio and Indiana.  Higher load meant higher power imports and voltage problems b/c local generation was inadequate to meet demand.  Additionally First Energy’s 600MW East Lake plant (Unit 5) removed a significant amount of generating capacity from the region.   This wasn’t a big deal. 
    2.  The real problem – as Maggie points out- is that First Energy had bad monitoring equipment.   Here’s the thing:  At 2:32 – a neighboring utility (AEP) called First Energy to tell them that their own 345kV line had tripped.  First Energy didn’t even know that one of its main Transmission lines wasn’t delivering power! 1950s technology, indeed. 
    3.  Up next, between 3:06 and 3:41, three more 345kV lines tripped off (without reseting) because of contact with ground vegetation.  These failures toppled First Energy’s network of 138kV lines.  Power was trying to find an alternative route around the unavailable 345kV paths and overloaded the 138kV circuits in a cascading fashion. One tipping point came with the trip of the Sammis-Star line (345kV)…which led to much of the Northeast blackout. 
    –Typically on high-load days Ohio and Michigan import power from efficient units to the South. As the 345kV trips started producing instability, islands started becoming disconnected (Cleveland was one of the first).  
    Cut of from the South, larger power draws were sourced from the West.  As these were overloaded, Michigan was quickly cut off from Ohio. Then Eastern and Western Michigan were cut off.  The only power into the state was coming down through Ontario. 
    As power from the South started shifting eastward to reach Michigan counter clockwise around Lake Erie, things started tripping off in PA, NJ, and NY. 
    This is when NY was cut off from its sources of power from the South. 
    Then Ontario–Michigan tripped.  
    Without power coming from the South, NYC started drawing power from Ontario – tripping lines and blacking out NYC. 

    All of this took only about 6 minutes.  

    Source: Electric Power Planning for Regulated and Deregulated Markets. 
    (Sadly, yes, I own a copy of this book.)

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