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What Happened in the UK Blackouts?

mitchoneill.com

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Re: What Happened in the UK Blackouts?

#161

Post by generatorguy »

7952 wrote: post #93
mitchoneill1 wrote: post #28

Earlier quoted context omitted.

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…

Is grid frequency not a good enough signal in its own right to increase production?

It is a perfectly good signal to increase production.

Re: What Happened in the UK Blackouts?

#162

Post by generatorguy »

fyfy18 wrote: post #3

What affect does the frequency drop have to home users? Is there protection in the substations near to homes that will cut off the power completely if the frequency goes out of range?

Not every substation but definitely the system is protected against over and under frequency and voltage so that loads can’t be fed 45 Hz for a minute.

Re: What Happened in the UK Blackouts?

#163

Post by growse »

caf wrote: post #155
growse wrote: post #119

Earlier quoted context omitted.

> Trains put into operation without the ability to survive a power transient without intervention. The trains were built to a environmental tolerance spec, and shutting down when that spec is exceeded seems like a reasonable thing to do. Having an expert test that all the safety systems are still working properly after they've been exposed to conditions they weren't designed for also seems prudent. Do you think peopl…

The GP says that the frequency drop was within-specification, not exceeding spec.

Which specification though? At the time they were being designed and procured, I think the specified tolerance for frequency change rate on the grid was 0.125Hz/s, but this was relaxed in 2014 to 1Hz/s (see https://www.nationalgrideso.com/document/10771/download). How much the effects of relaxing this on existing equipment was considered, it's not clear.

Similarly, the grid's license gives them a ±1% variation around 50Hz (so ±0.5Hz from https://www.nationalgrideso.com/balancing-services/frequency...).

So we have a power anomaly where the frequency moved >0.125Hz/s and dropped well below the 49.5Hz license threshold. I don't know what the procurement spec was, but I'd be very surprised if this event was "in-spec" for the trains, so in the absence if this it's probably reasonable to say that GP is incorrect.

Transformers get quite unhappily melty if you drop the frequency too much, so if your cooling system isn't designed to cope with this, it's probably better to shut down than have an exciting fire.

Re: What Happened in the UK Blackouts?

#164

Post by kalleboo »

circular_logic wrote: post #62
eDISCO wrote: post #10

Most traditional generators (think CCGT, nuclear, hydro) run in synchronous mode. Which means the generators spins with rpm proportional/equal to the network frequency. For 50Hz that would be 3000rpm. When the total electricity demand exceeds the supply, the kinetic energy of spinning generators is converted to electricity which slows down the generator rpm, which reduces the frequency. All synchronous generators on…

That makes me wonder, if you were standing next to these turbines would you be able to here them slow down?

This is kinda unrelated (it involved a line frequency slowdown from 60 Hz to 51 Hz), but I always found this radio recording of the US northeast blackout of 1965[0] fascinating as the DJ is grappling with records/tape cartridges slowing down and lights dimming live on the air https://www.musicradio77.com/images/ing11-9-65blackout.mp3

[0] https://en.wikipedia.org/wiki/Northeast_blackout_of_1965#Rad...

Re: What Happened in the UK Blackouts?

#165

Post by makomk »

growse wrote: post #163
caf wrote: post #155

Earlier quoted context omitted.

The GP says that the frequency drop was within-specification, not exceeding spec.

Which specification though? At the time they were being designed and procured, I think the specified tolerance for frequency change rate on the grid was 0.125Hz/s, but this was relaxed in 2014 to 1Hz/s (see https://www.nationalgrideso.com/document/10771/download ). How much the effects of relaxing this on existing equipment was considered, it's not clear. Similarly, the grid's license gives them a ±1% variation aroun…

The grid's license only requires them to be within ±0.5Hz of the nominal 50Hz for at least 95% of the time. Anyone designing a system which needs to operate reliably ideally ought to design it to operate over the full 47.5-52Hz range, or at least not fail so completely it cannot be restarted. Low frequency demand disconnect only starts at 48.8 Hz, ao any system that can't handle that is effectively setting itself up to be the first thing to fail when there's a power shortfall. This is utterly inexcusable for a train given the amount of disruption caused by multiple lines being clogged by failed trains in multiple places.

Re: What Happened in the UK Blackouts?

#166

Post by tripzilch »

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?

I am NOT a safety engineer, and I'm aware how complex that field is, so no, I don't believe that my personal hunches about what might have been a good idea intuitively are somehow better than these people whose actual job it is.

Hence my question about your background. But you implicitly answered that, too.

Re: What Happened in the UK Blackouts?

#167

Post by jhayward »

generatorguy wrote: post #160
jhayward wrote: post #131

Earlier quoted context omitted.

> but that battery in South Australia is only 100MW and the grid lost over 1400 MW I hear this kind of misconception fairly often and so it is worth noting that you don't need 1400 MW of battery to protect from this event. The initial 735 MW drop happened, as I read TFA, when a major generating source took itself offline as a result of the frequency disturbance . The later generator drops are cascades of the frequenc…

If 200 MW of generation trips instantly, which is typical when electrical equipment fails, you need 200 MW to replace it in the next few seconds, and then additional generation to bring the frequency back to Nominal. So far the largest battery is 40 MW? So not really going to help more than 40 MW can, even if it comes online instantly, when 200 MW trips off.

The point is to avoid the generator trip in the first place.

Re: What Happened in the UK Blackouts?

#168

Post by growse »

makomk wrote: post #165
growse wrote: post #163

Earlier quoted context omitted.

Which specification though? At the time they were being designed and procured, I think the specified tolerance for frequency change rate on the grid was 0.125Hz/s, but this was relaxed in 2014 to 1Hz/s (see https://www.nationalgrideso.com/document/10771/download ). How much the effects of relaxing this on existing equipment was considered, it's not clear. Similarly, the grid's license gives them a ±1% variation aroun…

The grid's license only requires them to be within ±0.5Hz of the nominal 50Hz for at least 95% of the time. Anyone designing a system which needs to operate reliably ideally ought to design it to operate over the full 47.5-52Hz range, or at least not fail so completely it cannot be restarted. Low frequency demand disconnect only starts at 48.8 Hz, ao any system that can't handle that is effectively setting itself up…

I don't disagree that a train that can tolerate a wider range is desirable, but lots of things are desirable. It's also desirable to give everyone their own carriage, or have a free bar on every train. But at what cost?

* Wider tolerance means heavier electrical and cooling systems, increasing both capital outlay and operating cost for both track wear and maintenance.

* The trains procured were essentially "off the shelf" from Siemens and would have been designed and manufactured for other operators before the DfT put the tender together. A wider operating tolerance would have therefore either ruled out the Siemens trains, or at least significantly upped the cost as they would have had to redesign them.

An annual season ticket from St Albans to London is about £3,600. How much more should that passenger (as well as the taxpayer) be paying so that they can travel on trains that work when this type of event happens? How often does this type of event happen?

> This is utterly inexcusable for a train given the amount of disruption caused by multiple lines being clogged by failed trains in multiple places.

People being stuck on trains for a few hours is pretty far down the severity list of "things that could go wrong" when the power goes out. That said, what I do think the outcome will be here is they'll figure out if/how the driver can self-reset this type of issue rather than requiring a fitter to travel out.

Re: What Happened in the UK Blackouts?

#169

Post by andygates »

mytailorisrich wrote: post #118
toyg wrote: post #57

Earlier quoted context omitted.

I would go as far as suggesting that these things should be routinely tested. In the UK most public buildings test fire alarms once a week; a programmed plan of localised, managed blackouts, to be carried out once every few years, would probably help in the long run - particularly as the grid is rapidly changing as described at the end of the post.

Of course they should be routinely tested. This is not a new idea and is an established best practice. This is why I am very surprised when I read that hospitals generators failing to take over is just "one of those things". It's like the 'old' saying that you don't have backups until you test recovery from backups...

We didn't hear about all the other hospitals that easily switched over to generators, just the one that failed. There's room for investigation there, but it's on the site, not the system.

Re: What Happened in the UK Blackouts?

#170

Post by dang »

mytailorisrich wrote: post #132
sergioj97 wrote: post #65

Earlier quoted context omitted.

I'm pretty sure there is a lot of people who is interested to know if this is someone's fault, and I don't think it has anything to do with how media covers this issues. I think it's a good thing, in fact. This failure may be within acceptable parameters and it may be simply meaningless to try to find someone truly responsible for it. But you seem to be unreasonably reluctant to believe that maybe it's not. I underst…

> But you seem to be unreasonably reluctant to believe that maybe it's not He seems to be working for National Grid or at least in the field so might be defending his own here or taking my comments personally.

Please don't cross into personal attack here.

https://news.ycombinator.com/newsguidelines.html

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