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From: Martin Brown <'''newspam'''@nonad.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: The Spanish Grid Drop-out - recently released information.
Date: Mon, 12 May 2025 15:36:05 +0100
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On 10/05/2025 17:58, John Robertson wrote:
> On 2025-05-10 9:46 a.m., Bill Sloman wrote:
>> One of my LinkedIn contacts - an IEEE contact in this case - posted 
>> some new data on LinkedIn, from a "Simon Gallagher, Managing Director 
>> at UK Networks Services | CEng | FIET | FEI | MBA "
>>
>> "We have had an update from ENTSO-E on the Spanish complete power 
>> failure. It is limited, but it helps to build the picture. I have 
>> updated our charts with the new information.
>>
>> Updated timeline:
>>
>> 1. Large generators in the South of Spain started to trip at 12:32:57 
>> CET. Over a period of 20 seconds a total of 2.2GW was lost – this is 
>> well beyond largest infeed so not secured against
>>
>> 2. The frequency looks to have been contained by system reserves until 
>> what looks like a large trip at 12:33:16
>>
>> 3. At this stage, the frequency falls at about 0.5 Hz/s for 4 seconds, 
>> until a rapid collapse starts
> ...

That is not unlike the failure in the UK Aug 2019 where an apparently 
inconsequential minor power station dropping off due to a lightning 
strike started a cascade failure that spread until they shed enough load 
to get a balance again. Wide area power cut resulted.

Green energy systems often react badly to frequency deviations. Whilst 
there is no reason why this should be the case it is frequently shown to 
happen. Some BESS systems *are* configured to maintain grid frequency 
but by no means all. They have the advantage of fast response but for 
that to be true they must not also be already running at full capacity.

Problem in the UK is that daytime load is such that everything that can 
is running close to the limits during the daytime with an evening peak 
that stresses the N-S interconnectors even in summer. I noticed last 
week one evening at peaktime that the supergrid power cables were 
visibly sagging as a result of the current flowing through them. I'd 
never really noticed that before but I expect it happens all weekdays.

>> "While I think a lack of inertia had an impact here, that does not 
>> mean that the level of solar and wind was to blame - rather it is how 
>> it has been integrated - more grid forming inverters, more rotating 
>> mass is needed, I suspect."
>>
> 
> Perhaps for systems that have large solar or wind arrays they could use 
> a number of large rotating masses to smooth over these burps? Vacuum and 
> magnetic bearings...

They are intrinsically dangerous if they store enough energy to really 
matter. We had such a steel reinforced lead flywheel and motor generator 
configuration on big radio telescopes storing just enough energy to stow 
them in the event of a storm taking out 3 phase mains power. The dishes 
can only reliably survive storms if they are pointed at the zenith.
(sometimes not even then)

Working out how far it would travel if it ever broke free from its very 
substantial bearings was used as an exam question. It was installed 
pointing so that it would not hit any property if it did.
> 
> I imagine a series of rotating masses so if any single or several fail 
> (earthquake, etc.) the system wouldn't collapse.

Magnetic levitation vacuum pumps were all the rage when I was in Japan. 
That was until one day the entire world moved an inch to the left. Every 
last one of them crashed with shattered titanium blades everywhere and 
no vacuum/moist summer air in the chambers. Hell of a mess. After that 
we went back to conventional bearings in all earthquake countries.

> As you say, there is little inertia in these solar systems unlike water 
> or fuel generated power.

The advantage of gas turbines or diesel generators is that when the 
rotor starts to slow it automatically increases the gas supply to try 
and maintain frequency. The stored energy in the rotor is significant 
but it it have the ability to output a bit extra or a bit less in 
response to changing load that makes them so handy for stability.

The other alternative is to have loads of last resort that can be shed 
at any time to compensate for loss of generating capacity, but losing 
2.2GW in a single shot over 5s would severely test most networks.

-- 
Martin Brown