Anatomy Of A Power Outage: Explaining The August Outage Affecting 5% Of Britain

Without warning on an early August evening a significant proportion of the electricity grid in the UK went dark. It was still daylight so the disruption caused was not as large as it might have been, but it does highlight how we take a stable power grid for granted.

The story is a fascinating one of a 76-second chain of unexpected shutdown events in which individual systems reacted according to their programming, resulted in a partial grid load shedding — what we might refer to as a shutdown. [Mitch O’Neill] has provided an analysis of the official report which translates the timeline into easily accessible text.

It started with a lightning strike on a segment of the high-voltage National Grid, which triggered a transient surge and a consequent disconnect of about 500MW of small-scale generation such as solar farms. This in turn led to a large offshore wind farm deloading itself, and then a steam turbine at Little Barford power station. The grid responded by bringing emergency capacity online, presumably including the Dinorwig pumped-storage plant we visited back in 2017.

Perhaps the most interesting part followed is that the steam turbine was part of a combined cycle plant, processing the heat from a pair of gas turbine generators. As it came offline it caused the two gas turbines feeding it to experience high steam pressure, meaning that they too had to come offline. The grid had no further spare capacity at this point, and as its frequency dropped below a trigger point of 48.8 Hz an automatic deloading began, in effect a controlled shutdown of part of the grid to reduce load.

This is a hidden world that few outside the high-power generation and transmission industries will ever see, so it’s very much worth a read. It’s something we’ve touched on before with the South American grid shutdown back in June, and for entirely different reasons in 2018 when an international disagreement caused the entire European grid to slow down.

Header image: Little Barford combined-cycle power station against the sunset. Tony Foster, (CC BY-SA 2.0).

18 thoughts on “Anatomy Of A Power Outage: Explaining The August Outage Affecting 5% Of Britain

  1. Many years ago I was working in the offices of a major chemical company next to one of their manufacturing sites. They had their own power plant (partially because they used a lot of steam, so they could use the exhaust from the turbines). One day one of the turbines failed, and as part of the shutdown process dumped its load onto the next turbine in the row. This overloaded that turbine, which shut down and cascaded down the whole plant. The first thing we knew about it was PCs browning out and shutting down. Recovery from that event took days, not from getting the electricity back, but from cleaning out and unblocking the processes that used the steam.

    1. “The technical term for “deloading”, which is a made up word, is “load shedding”.”

      Maybe that’s British English, they make up words, and misuse many, almost like they aren’t speaking English at all…

      I’m wondering if our own power grid might be heading toward similar problems, same age, or older. Similar low priority for upgrading. Britain has been doing the ‘green’ think, a little more enthusiastically, than Trump, guess that turn out to be a good thing. Least we know we need to do some work, as we incorporate renewable sources, with our fossil grid. The ‘wait, until breaks’ mindset of Congress, sort of leads me to believe the ‘Green New Deal’, is going to be a catastrophic mess, and way more expensive than estimated. Hopefully, the democrats will take the next 5 1/2 years, to work out some of these details, maybe figure out how to pay for it all.

    2. Both terms are legitimate, but describe different things. Deloading is when a generator disconnects from the grid, either manually or automatically. Load shedding is when customers are cut off from the grid, usually as an automatic measure to restore mains frequency.

  2. I’m seeing a few things come out of this.

    1) The increasing use of smaller plants (wind/solar/other) are causing a decrease in grid stability. Each individual system is less able to accommodate unexpected changes in load leading to tripping off-line.

    2) The automatic systems are in place to protect the hardware and prevent damage to the grid (loss of power is not damage, having to buy a new generator is damage). The recovery process is manual and not automatic as the operators will need to figure out if it is safe to return to normal operation and not cause additional issues. (Computers are stupid and fast, humans are smart and slow)

  3. Twenty years in steam and gas turbine gen sets, (Small ones, 50MW and smaller) we had the occasional load shedding event. It can get exciting, but not as exciting as the Nukes.
    Some failures are here:

    And back in the day: The solar storm of 1859 (also known as the Carrington Event) was a powerful geomagnetic storm during solar cycle 10 (1855–1867). A solar coronal mass ejection (CME) hit Earth’s magnetosphere and induced one of the largest geomagnetic storms on record, September 1–2, 1859. The associated “white light flare” in the solar photosphere was observed and recorded by British astronomers Richard C. Carrington (1826–1875) and Richard Hodgson (1804–1872). The storm caused strong auroral displays and wrought havoc with telegraph systems. The now-standard unique IAU identifier for this flare is SOL1859-09-01.

    A solar storm of this magnitude occurring today would cause widespread electrical disruptions, blackouts and damage due to extended outages of the electrical grid. The solar storm of 2012 was of similar magnitude, but it passed Earth’s orbit without striking the planet, missing by nine days.

    1. Thank you for this most probable report of the Carrington Effect that could have happened in more recent times if only more read up about these happenings as a probable cause to more modern times of mass power lines outrages now and with these recent times of heavy geomagnetic solar storms now the sun has turned into a solar minimum and replaced by solar flair maximum that occasionally come our way when the flair direction and our country do line up which can and dose happen. But as it’s invisible and only tracked be electromagnetic radiation meters that people do not use these stoms are not blamed for these vast area of more than one power sources like solar, wind and turbine power generation. It’s More probable that this libe onethe case than one lightening storm to make all three power sources cuting out at one time, as solar radiation can cover wider areas than a single electrical storm strike.

  4. Interesting read. I was stuck in the middle of this on a train heading for London, and never made it. The power outage didn’t seem to be the main issue, as it was restored quite quickly. According to the driver of our train, it was the ‘more modern’ trains ahead of us weren’t able to restart as their control systems were upset by the glitch and they couldn’t reboot them! Our train was a bit more vintage and made it to the next station when the power was restored, but couldn’t go further due to the other trains blocking it. Another example of a failure cascade, I guess.

    1. That’s the same as what I heard from one of my colleagues stuck on one of those modern trains. Engineers had to travel one by one to each of those trains to restart the control systems in some manual fashion.

  5. We had a similar event here in Adelaide a year ago: wind took down a major transmission line and caused a bunch of wind generators to trip offline either due to not actually being on the grid anymore, or grid frequency fluctuations. A few minutes later, the whole state (about 1.7M people) lost power entirely, and it was about 5 hours before it began to be restored.

    But of course here in Australia, we have a coal-powered government and significant anti-renewables lobby so they instantly (before the power was back on) blamed the wind generators for the blackout because South Australia has a lot of wind turbines. It caused a lot of really dumb internet arguments and even dumber right-wing television.

  6. Incredibly strong parallel to the cascade failures with cloud infrastructure. All very well designed, but when the s hits the fan, the fallout can be bigger than expected. Maybe we (as engineers) need to be trained to be more pessimistic about the base layers we depend on. :)

  7. When the power blinks I count’ that’s one, that’s two, and that’s three. When get to three I know the power is going to be off for awhile, unless it’s a simple repair. One time when fueling my pickup the power cut. I wrongly assumed that place had a backup generator. Because of all the refrigeration, and whoever had back up power would be the one supplying fuel to first responders if needed.

  8. I don’t know if this report mentions it specifically but the trains that failed to restart were modern (Siemens?) ones which were (by the sound of it) fairly hard-coded not to start if the frequency was below a fairly tight tolerance, and they had to send a man out with a laptop to reset (or possibly reconfigure) every individual train.

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