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What Happened in the UK Blackouts?

mitchoneill.com

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Re: What Happened in the UK Blackouts?

#41

Post by aurbano »

It actually sounds like this was really useful though, as a lot of the systems involved will be improved in the future.

I'm not sure if the grid is already doing this, but they should trigger failures randomly, including Low Frequency Demand Disconnection schemes from time to time to ensure that all downstream systems are also ready (like the hospital someone mentioned that had an issue with the backup generator, or the trains that stopped working when the frequency failed). A bit like caos monkeys in dev environments.

Re: What Happened in the UK Blackouts?

#42

Post by Zenst »

mytailorisrich wrote: post #31
tripzilch wrote: post #23

Earlier quoted context omitted.

Do you have background in the field of giant power supply fault tolerance backup mishap management strategies, or something? Or are you just stating and assuming all of this is obvious, covered by standard planning, instead of easy to say in hindsight? Cause you're making a lot of statements, saying it is such, without backing it up. Maybe it is super obvious, but personally I'm impressed by the strategies that were…

Would you not prioritise an airport, a hospital, the railway, over residential areas? Do you not think that trains should be able to resume ASAP? Do you not think that "it never happened before" is not a valid reason to be unprepared? Do you not think that "we never had to use it before" is not a valid reason to explain why an emergency generator might not work when needed? What backing up do you need?

"Would you not prioritise an airport, a hospital, the railway, over residential areas?" Yes and they do.

As mentioned, things get added to the grid all the time, case of the airport was that it was not on a priority list. Yes that is an oversight, but who's fault and accountability we do not know. The onus would of been in the airport to inform the power distribution and if that failed to happen then the airport would be the ones with the hands up, if they was and the distribution failed to add it, then their hand would go up.

But hospitals as I mentioned operate and a designed and planned for such issues with them having backup power supplies. Which is the solution for many installations as many will not have or justify the cost of being upon their own distribution spur.

As for the "we never had to use it before" that's down the testing and covered in previous comments fairly well without repeating it again.

But if you wish to focus upon being able to point a finger at somebody and say it is there fault, then fine. But I and I'm sure many others would not be focusing upon that, though I can appreciate that mentality due to the way media/tabloids cover such and all issues in life. After all, power cuts today are not that common on this scale, decades past and in less developed countries they would be so common that they wouldn't even make the news.

But remember, if the weather forecaster says it will not rain and you go out and a light shower makes you wet - would the forecast be wrong or would we have the mentality to go, that mistake was within acceptable parameters and just one of those things. It gets down to what we are used to and what we accept. So yes, I get that blame need to be lain in many eye's but is that fair all the time?

But then - nothing is perfect - better to focus on getting closer to perfection than expending energy stagnating as too busy pointing the finger.

Re: What Happened in the UK Blackouts?

#43

Post by techsupporter »

rwmj wrote: post #33

Why does frequency drop when the system is overloaded?

Imagine if you are running on a conveyor belt at 60 steps per second. This belt is turning a crank that, let's say, moves water. You are the energy input (the sun for solar, heat energy for steam turbines, movement of wind for windmills, and so on), the crank is the generator, and the water is the load.

Now imagine the water is suddenly turned into vegetable oil (more load has come on). It is more difficult to move. For a brief moment, your energy input is still the same but you can't push as much of the new liquid so your pace slows down a bit, to 58 steps per minute. You increase your exertion (add more energy input) and your pace climbs back to 60 steps per minute.

Finally, imagine that you're running as hard as you can. That 60 steps per second to push that vegetable oil is as much as you can do. But the vegetable oil turns to heavy cream (even more load). You've put in as much energy as you can but your pace falters and drops to 49 steps per second.

That's why the frequency falls.

Re: What Happened in the UK Blackouts?

#44

Post by radiowave »

pedrocr wrote: post #27

Isn't this kind of fault a good argument for synchronizing the UK grid to the rest of Europe? They seem to already have an interconnect that's of the scale of demand needed here, but it's a DC link.

If they were synchronized, it would mean that in the case of any larger failure that would draw too much current over the undersea link, the link itself would have to trip out.

Re: What Happened in the UK Blackouts?

#45

Post by FPGAhacker »

rwmj wrote: post #33

Why does frequency drop when the system is overloaded?

For the same reason a car engine’s RPMs will drop when you start going up a hill (unless you increase the throttle).

Spinning up the generators, and keeping them spinning, takes energy on top of whatever the load is. If the load increases, but the input energy does not, the difference is robbed from the momentum of the spinning mass. This slows the generators down thus the frequency drops.

Re: What Happened in the UK Blackouts?

#46

Post by pm215 »

kzrdude wrote: post #22

At one stage, they have to shed load (turn power off), and that sounds totally reasonable. How are these areas divided, how does one turn power off for a whole area, and how is it decided who to cut from power (temporarily)?

https://www.westernpower.co.uk/downloads/4093 is a pdf for one of the local power distribution companies that includes an explanation. The short answer is that they have frequency-sensitive relays that automatically disconnect some or all of the feeders downstream of 132kV substations as frequency drops through various specified limits.

Re: What Happened in the UK Blackouts?

#47

Post by guerby »

mitchoneill1 wrote: post #28
pm215 wrote: post #20

The article says near the bottom "At the time [the GT1A generator tripped] there was 4000MW of unused generation in reserve, and if only a fraction of this reserve was instructed to dispatch within 60 seconds of the initial loss it’s very likely that load shedding would have not occurred." My understanding was that having reserves available within 30-60s was pretty expensive, and that that would have been what was us…

Hey! (author of the article here). I'm not happy with how I phrased this with the 4GW of capacity -- and while I suspect generation could have increased by hundreds of MW within 60 seconds I may be wrong. I've updated how I've phrased it in the blog to hopefully give a bit more clarity to my position. I don't meant to suggest that plants could ramp full within 60 seconds, it's that 4GW means there's a bunch of headro…

I assume battery based grid power stations like the Tesla one in Australia are amongst the best in class to help in this kind of crisis situation? Compared to the gaz turbine the system it is simpler (no mehanical/heat/fluid parts) and depending on design will likely never be completely off since made of dozens or hundreds of independant equipement (batteries and inverters).

Thanks for the article and comment!

Re: What Happened in the UK Blackouts?

#48

Post by mytailorisrich »

Zenst wrote: post #42
mytailorisrich wrote: post #31

Earlier quoted context omitted.

Would you not prioritise an airport, a hospital, the railway, over residential areas? Do you not think that trains should be able to resume ASAP? Do you not think that "it never happened before" is not a valid reason to be unprepared? Do you not think that "we never had to use it before" is not a valid reason to explain why an emergency generator might not work when needed? What backing up do you need?

"Would you not prioritise an airport, a hospital, the railway, over residential areas?" Yes and they do. As mentioned, things get added to the grid all the time, case of the airport was that it was not on a priority list. Yes that is an oversight, but who's fault and accountability we do not know. The onus would of been in the airport to inform the power distribution and if that failed to happen then the airport woul…

You protest a bit too much at this point, methinks.

I am commenting that the scale of the disruption resulting from (only) a 5% drop does not seem reasonable and that some of the issues should have been better handled or avoided altogether.

> But I and I'm sure many others would not be focusing upon that, though I can appreciate that mentality due to the way media/tabloids cover such and all issues in life

That's a personal attack quite out of order.

Re: What Happened in the UK Blackouts?

#49

Post by timthorn »

pbhjpbhj wrote: post #32
pm215 wrote: post #20

The article says near the bottom "At the time [the GT1A generator tripped] there was 4000MW of unused generation in reserve, and if only a fraction of this reserve was instructed to dispatch within 60 seconds of the initial loss it’s very likely that load shedding would have not occurred." My understanding was that having reserves available within 30-60s was pretty expensive, and that that would have been what was us…

Might be pumped water storage like "Electric Mountain" in North Wales (there's some in Scotland too, not sure what the total pumped storage on the grid is). They pump water to remove excess power from the grid and then run in reverse to generate. Their 0-100% is O(1minute) IIRC, actually on the website they say: >"Synchronised and spinning-in-air emergency load pick-up rate from standby: 0 to 1,320 MW in 12 seconds"…

It's also one of the plants capable of restarting the grid from a complete blackout.

Re: What Happened in the UK Blackouts?

#50

Post by pm215 »

aurbano wrote: post #41

It actually sounds like this was really useful though, as a lot of the systems involved will be improved in the future. I'm not sure if the grid is already doing this, but they should trigger failures randomly, including Low Frequency Demand Disconnection schemes from time to time to ensure that all downstream systems are also ready (like the hospital someone mentioned that had an issue with the backup generator, or…

Triggering demand disconnection randomly is saying "we should provide consumers a service including deliberate random blackouts". That's OK in contexts like Netflix where the downstream systems are supposed to be able to be resilient to faults and failures are comparatively low-stakes anyway. But almost all grid consumers aren't resilient to power loss (would your house continue to be fully functional without noticeable ill effects if power to it went out? Mine wouldn't...) and even for industrial scale consumers who do have generators the costs of finding out in a deliberate blackout that their generator was faulty could be anything from expensive to life-threatening.
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