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?
One quirk of synchronous generators is you can think of the whole grid like all of the generators in it are geared together. If demand rises, the torque on the generators starts to increase and if the power plants don't feed more mechanical power in then they will start to slow down in unison. Likewise their speed will increase as the demand drops. So the frequency is the main indicator of the health of the grid and so the grid operators will monitor it closely.
So I thought and then we had a multi week frequency shift in the EU and various clocks started lagging behind. This does show up for consumers as well.
So sometimes they will run slightly above target and sometimes they will let it run slightly below target. Ordinary daily demand cycles help.
The problem is mostly at the generation end. The electrical grid is essentially distributed transmission locking all the generators across country together. They will all rotate in sync at the same speed/phase, it might as well be a mechanical linkage.
The entire system is under too much load and the generators are all physically slowing down. Unfortunately the generators are all designed to operate over a very narrow frequency range. If the frequency continues to drop, the safety systems will kick in to protect the generator.
If the load isn't reduced, more and more generators will drop off the network and there will be less and less supply to meet the demand. The frequency will drop lower and lower. Eventually the whole network will drop to zero and nobody will have power.
It's basically the same thing as stalling an engine.
The emergency response kicks in not because 49 is innately very bad and 48 is some horrible evil by itself, it kicks in because if you do nothing, then in a few minutes you're going to see 40, 30 and the whole system is going to stop - or, more realistically, every connected subsystem (both generators and consumers) will have their emergency responses kicking in and either shutting down or automatically disconnecting from your system.
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.
>"In Japan, the western half of the country runs at 60Hz, and the eastern half of the country runs at 50Hz – a string of power stations across the middle of the country steps up and down the frequency of the electricity as it flows between the two grids." //
That's, err, curious.
> Eastern Japan (including Tokyo, Kawasaki, Sapporo, Yokohama, and Sendai) runs at 50 Hz; Western Japan (including Okinawa, Osaka, Kyoto, Kobe, Nagoya, Hiroshima) runs at 60 Hz. This originates from the first purchases of generators from AEG for Tokyo in 1895 and from General Electric for Osaka in 1896.
https://en.wikipedia.org/wiki/Electricity_sector_in_Japan#Tr...
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...