What Happened in the UK Blackouts?
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What Happened in the UK Blackouts?
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Re: What Happened in the UK Blackouts?
#2"Frequency drops below 48.8Hz which triggers the Low Frequency Demand Disconnection scheme (LFDD). Approximately 1GW (5% of total) of Great Britain electricity demand is turned off."
Is interesting as it highlights the importance of managed failure. Things fail, but the ability to see those failures and control how that fails is important. Had such an action not been taken, the result would of been a far greater outage/impact and more so an outage that you had no idea what parts it would impact.
Re: What Happened in the UK Blackouts?
#3What 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?
Re: What Happened in the UK Blackouts?
#4What an interesting read! I had no idea that a blackout happened in UK recently, so I clicked out of curiosity and was rewarded with this delightful description of the initial events.
It's also interesting to see the interplay of automated and manual systems in such a complicated scenario.
Re: What Happened in the UK Blackouts?
#5What 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?
The main problem with frequency mismatch is that when two power sources "meet" with different frequency the effect can be catastrophic, because the faster generator pulls the slower (think of the "hares" in 3000-10000 m running competitions) and typically both end up breaking.
Re: What Happened in the UK Blackouts?
#6"Frequency drops below 48.8Hz which triggers the Low Frequency Demand Disconnection scheme (LFDD). Approximately 1GW (5% of total) of Great Britain electricity demand is turned off." Is interesting as it highlights the importance of managed failure. Things fail, but the ability to see those failures and control how that fails is important. Had such an action not been taken, the result would of been a far greater outa…
The issue with this specific outage is that it was badly managed.
The main gripe people and authorities have with what happened is that key infrastructures immediately lost power. When (only) 5% of demand is turned off this should not impact railways, airports, and hospitals.
Beyond the initial loss of power other problems amplified the consequences: For example, trains could not just restart but required specialist staff to attend each of them to get them through a specific procedure, which turned a short power loss into hours of delays.
This highlights the importance of looking at systems globally. The grid is just one part of the system.
Re: What Happened in the UK Blackouts?
#7What 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?
For anything powered by a Switch Mode Power Supply/SMPS (TVs, computers etc) then not much effect, as power is rectified immediately and then converted back several 10s of KHz, and so many SMPS devices will actually run from DC.
Heating elements (kettles etc), also don't care, and a lot of motors used in household items are universal motors[1], which will end up running at the same speed even as the frequency drops. Old alarm clocks do use the mains supply as a time reference though, so they will end up having the wrong time, as happened recently in the European grid [2].
For a transformer, efficiency decreases rapidly[3] with falling frequency. For household usage, transformers running directly on mains frequency are only used for linear power supplies (as opposed to the SMPS supply used earlier) which found in things like audiophile level power amplifiers (adds a nice bit of weight), so your Class-A amplifier may get even hotter.
The power grid uses transformers of course, to step down the several kV supply to the 240V used in the UK, and its possible that a big enough frequency shift could cause overheating of these from the decreased efficiency. I would be very surprised if they would not turn off if they got too hot though, it seems like a sensible thing to design in.
In short, not much for small changes, but the frequency is falling as there is more consumption than supply, so the supply gets turned off to decrease demand.
[1] https://en.wikipedia.org/wiki/Universal_motor [2] https://www.irishtimes.com/news/world/europe/clocks-in-25-co... [3] https://electronics.stackexchange.com/questions/23999/effect...
Re: What Happened in the UK Blackouts?
#8What 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?
The main problem with frequency mismatch is that when two power sources "meet" with different frequency the effect can be catastrophic, because the faster generator pulls the slower (think of the "hares" in 3000-10000 m running competitions) and typically both end up breaking.
Nice article covering frfequncy importance at grid level:- https://www.drax.com/energy-policy/need-whole-country-freque...
Though I'm not sure on the details of a frequency drop and impact upon your house in exacting details. Equally I'm not up on substations (did work on IT for large util company many decades ago, but not field engineering). But the first safety control from supply to the home, would be the distribution transformer and those back then had overheat protection. Also had a flag attached by wax at one spot, so if they did overheat and cut out for a while, you could visualy see that due to the flag being visible. But that was more a legacy solution that still prevailed into the 80's, unsure about now. But would not be supprised if such tried and tested things still take place as some form of backup monitoring. I learned about it after coding for a database that stored such records that had the field name SITESHIT, which was short for "SITES HIT", yes - you can see how that gave a young humble COBOL programmer a laugh. But it would be a count of how many times that wax flag had been triggered.
Re: What Happened in the UK Blackouts?
#9[deleted]
Re: What Happened in the UK Blackouts?
#10Most 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 a given network spin at the same frequency, so when the demand is too high all of them slow down a bit.