You are correct that grid frequency is allowed to wander, but that there is a general requirement to keep it to a long term average of 50 or 60Hz. Grid codes specify the limits,which include the levels at which automated disconnection is supposed to cut in, and the maximum normally permitted limit for larger deviations. In GB they are supposed not to let frequency drop below 49.5Hz for more than a minute, and the first shedding frequency is 48.8Hz. Normal permitted operation is +/-0.2Hz around 50Hz. I'd have to look up the cumulative clock error that requires correction.

Here's a print from Ercot at the key moment of the Texas blackouts 8n Feb 21

https://web.archive.org/web/20210215075245/http://www.ercot.com/content/cdr/html/real_time_system_conditions.html

The print recorded at 59.334Hz is a hair's breadth above the 59.3Hz LFDD level, and you can be sure there were places on the network that thought they saw 59.3Hz and disconnected demand circuits, maybe a second later given the speed of fall of the frequency, although the official report tries to deny that happened and pretends that the control room selected cuts. The cumulative clock error is over 25 seconds slow with 8 successive minutes of increase. There was a cascading trip of generators in progress, likely triggered by the rate of change of frequency as there was no reserve left to arrest the fall, each trip making it worse.

There are attempts to set looser standards for frequency to try to make the grid more robust to the sort of frequency excursions that become a regular feature with increased renewables penetration and dependence on interconnectors that can suddenly trip out, sending frequency suddenly wildly higher or lower. At the same time, grid reinforcement with batteries that are supposed to leap into action and statcoms and synchronous condensers have become de rigeur. Lowered grid inertia speeds the rate at which events get out of control. It's an accident waiting to happen.

GB got close to some blackouts on 22nd December last year. Initially 1GW of IFA interconnector I port tripped our, allegedly followed by a small CCGT generator. However, the frequency fell to 49.275 Hz, which implied a much bigger loss of generation that has not been officially admitted, although some grid traders reckoned it included a bunch of wind in Scotland. It seems that the Grid batteries failed to stomp on the original trip for reasons that are unclear: there are plenty of previous examples where they coped well with even 1.4 GW loss on NSL. Officially it took 59 seconds to restore frequency above 49.5Hz, thus avoiding a rather more in depth official investigation. I do wonder if a print was "corrected". The main correction came from pumped storage about 12 seconds after the initial trip. If that had been 4 seconds later there would have been blackouts.

DaveS,
Well spotted. I hadn't noticed that both links involved Fenix*. Fully agree that the cause of the fire is not that important. When it comes to fires, EV batteries really can turn molehills into mountains. Also agree with your "tangent". The Scottish government wanted power: downwards, or upwards, anywhere they could get it. They're not alone.

(*)Fenix is presumably based on the phoenix, whose link with fire seems appropriate.

It doesn't add up...,
By "grid synchronisation authority" I had in mind a body whose sole purpose was to dictate the phase of the sine wave around the country in a suitably bureaucratic manner. They might come up with something linked to a well-regulated concept like UTC (until they get blindsided by a leap second). There's nobody does that at the moment because it'd be a very stupid idea. And that's why I half expect somebody's going to try to make it happen.

Certainly there needs to be somebody looking after the grid, keeping the waveform as clean as possible, and the lines below power limits, but the waveform necessarily fluctuates in frequency as load varies, so synchronisation comes down to synchronising with what's already on the line. No central authority needed.

When I worked at the NSW Electricity Commission, I recall their key rule for frequency was that the *average* should be 50Hz because so many devices relied on the AC waveform to keep their clocks accurate. I think they typically tweaked overnight generation to compensate for any drift through the previous day. (I wasn't in generation, so may be talking through my hat)

tomo,
I've been interested reading about optimal charge/discharge strategies too. Optimal longevity strategies seem to be holding (roughly) between 50 and 75% capacity. That is only 25% of the whole range, so your 200 mile battery is best recharged (to 75%) after only 50 miles. Or, alternatively, your 200 mile battery really has enough oomph for 800 miles, but a conservative charge management system only makes 200 miles available. Either seems pretty extravagant.

We'll see in due course how Tesla goes with its warranties. There are plenty of businesses whose "money-back guarantee" has proved worthless when they have gone insolvent as the claims started rolling in. It'll set quite a high-water mark if that happens with Tesla!

All grids have a grid synchronisation authority, usually known as a TSO - Transmission System Operator. They all have their mechanisms for charging out their costs to consumers. In GB these are classified as TNUoS, DNUoS and BSUoS, for high voltage transmission, lower voltage distribution and system balancing respectively. That is in addition to the allocation of billing for electricity supplied which gets refined as meter readings come in. Things like V2G and "Demand Flexibility" depend on aggregated smart meter readings made by retailers at half hour resolution. Some of the local distribution outfits now have quite detailed power flow information across their networks, and some are beginning to make information available publicly to help decide on possible new connections for demand or batteries and generation.

https://www.ssen.co.uk/our-services/tools-and-maps/near-real-time-data-access-nerda-portal/

With talk of locational marginal pricing in future such information becomes essential. So far the government has been scared to go the whole hog on LMP , which could lead to some extreme local prices (both positive and negative), talking of just regional pricing - and ToU pricing.

@Robert

I can't help noticing that the Ayrshire battery recycling plant that had the fire you linked to on Apr 9 is owned by Fenix Battery Recycling Ltd, the subject of one of your links provided on Apr 11. That article was dated 2021. So we know that Fenix is still operating, but can conjecture that they haven't sorted all the problems out yet. Of course, the actual cause of the fire might have had nothing to do with the EV batteries stored on site awaiting processing, but clearly the presence of these batteries in a blazing building caused big problems for the fire fighters.

Going off on a tangent, I was unaware that there is now a Scottish Fire & Rescue Service, which has apparently existed since 2013. It's funny how in Scotland, since 'devolution' services that were once devolved to regional level have systematically been centralised.

tomo,
I wonder how it's going to go with Tesla and their 8 year battery warranty with a promise of still having 70% capacity. That's just the headlines I've read about their warranty. Perhaps there's some fine print about how many miles have been clocked up, or how many recharge cycles.

Agreed on the synch mechanism, but in these days of engineering by government edict, I wouldn't be surprised if some minister somewhere wasn't thinking of creating a "Grid Synchronisation Authority".

I looked at that battery recycler's site. Only read one article (on the challenges of EV battery recycling). A bit arm-wavy about the problems, and their plan was basically we'll work with clever people from Birmingham Uni to sort it all out. They did have an interesting factoid in there that 99% of lead-acid batteries get recycled. They claimed: that recycling rates for lithium-ion batteries could be as low as 5%. I suspect they could be substantially lower than that...

Thanks for the link to the hydro plant catastrophe. Interesting to hear what they were up to when electricity was at peak pricing. Still, what's the point of a margin of safety if you can't abuse it from time to time? (I mean the warp drive always took it in spite of Mr Scott's protestations that it couldnae)

MikeHig,
If V2G were ever to get going, there'd be a question of who pays the grid operator. Even when doing the neighbourly siphoning thing, the wires are providing a service and somebody should be paying. It would seem fair that I pay to put my power onto the grid, and my neighbour pays to receive it from the grid. I suppose this is kind of built into the low feed-in tariffs paid for rooftop solar.

DaveS,
The generators were painted green. Doesn't that take the curse off it?

On a completely different topic, here's a very good video on what exactly is going on under the covers of ChatGPT. It's by 3Blue1Brown, who does brilliant mathematical videos. I remember his earlier introduction to neural nets was very good. The new one gives an insight to the staggering amount of computation going on in ChatGPT.

Anyone who thinks this has anything to do with cognition, or the computer understanding what it's doing, might need their own thought processes looked into.