4 ms·

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 frequ

by fyfy18 7y ago

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?

bonzini 7y ago
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.
- Zenst 7y ago
  Nice article covering frfequncy importance at grid level:- https://www.drax.com/energy-policy/need-whole-country-frequency/ 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.
  - bonzini 7y ago
    That website has had me nerd-sniped. Another great one is on "black start": https://www.drax.com/technology/black-start-important-back-plan-youve-never-heard/ https://www.drax.com/technology/black-start-important-back-p...
    - spzb 7y ago
      You might also enjoy this one http://www.gridwatch.templar.co.uk/index.php http://www.gridwatch.templar.co.uk/index.php
  - pbhjpbhj 7y ago
    From that article: >"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.
    - stordoff 7y ago
      It's largely a historical artifact: > 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#Transmission https://en.wikipedia.org/wiki/Electricity_sector_in_Japan#Tr...
snops 7y ago
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 https://en.wikipedia.org/wiki/Universal_motor [2] https://www.irishtimes.com/news/world/europe/clocks-in-25-countries-to-make-up-for-lost-time-1.3421280 https://www.irishtimes.com/news/world/europe/clocks-in-25-co... [3] https://electronics.stackexchange.com/questions/23999/effects-of-changing-the-frequency-of-a-transformer https://electronics.stackexchange.com/questions/23999/effect...
phire 7y ago
Most things in a modern home don't care about frequency. 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.
rcxdude 7y ago
The grid frequency itself doesn't matter much as far as consumers are concerned, the deviations mentioned in this article would not cause any problems for a home user directly (or even generators, but as mentioned below if it is too far out of range generators start to need to cut out) but it is a far better indicator of the general balance of supply and demand of power in the grid than any other metric, because it can be measured very precisely, isn't subject to local effects like voltage, and correlates well with the state of the generators. 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.
- the_mitsuhiko 7y ago
  > The grid frequency itself doesn't matter much as far as consumers are concerned 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.
  - jacques_chester 7y ago
    Generally grids try to average out to their target frequency over some period (24hrs, for example) because so many timekeeping systems rely on counting cycles. So sometimes they will run slightly above target and sometimes they will let it run slightly below target. Ordinary daily demand cycles help.
PeterisP 7y ago
A small frequency drop doesn't have a major impact to home users as well, but it's a symptom of a generation/consumption mismatch - the frequency dropping from 50 to 48.8 is a sign that the consumption is draining energy that's not generated by essentially taking it from the inertia of the major generators, and temporarily reducing consumption as all the large phase-linked motors are suddenly slowing down slightly... both of which are temporary, short-term, unsustainable effects. 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.
generatorguy 7y ago
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.

by fyfy18 7y ago

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?

bonzini 7y ago

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.

Zenst 7y ago
Nice article covering frfequncy importance at grid level:- https://www.drax.com/energy-policy/need-whole-country-frequency/ 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.
- bonzini 7y ago
  That website has had me nerd-sniped. Another great one is on "black start": https://www.drax.com/technology/black-start-important-back-plan-youve-never-heard/ https://www.drax.com/technology/black-start-important-back-p...
  - spzb 7y ago
    You might also enjoy this one http://www.gridwatch.templar.co.uk/index.php http://www.gridwatch.templar.co.uk/index.php
- pbhjpbhj 7y ago
  From that article: >"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.
  - stordoff 7y ago
    It's largely a historical artifact: > 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#Transmission https://en.wikipedia.org/wiki/Electricity_sector_in_Japan#Tr...

snops 7y ago

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 https://en.wikipedia.org/wiki/Universal_motor [2] https://www.irishtimes.com/news/world/europe/clocks-in-25-countries-to-make-up-for-lost-time-1.3421280 https://www.irishtimes.com/news/world/europe/clocks-in-25-co... [3] https://electronics.stackexchange.com/questions/23999/effects-of-changing-the-frequency-of-a-transformer https://electronics.stackexchange.com/questions/23999/effect...

phire 7y ago

Most things in a modern home don't care about frequency. 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.

rcxdude 7y ago

The grid frequency itself doesn't matter much as far as consumers are concerned, the deviations mentioned in this article would not cause any problems for a home user directly (or even generators, but as mentioned below if it is too far out of range generators start to need to cut out) but it is a far better indicator of the general balance of supply and demand of power in the grid than any other metric, because it can be measured very precisely, isn't subject to local effects like voltage, and correlates well with the state of the generators. 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.

the_mitsuhiko 7y ago
> The grid frequency itself doesn't matter much as far as consumers are concerned 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.
- jacques_chester 7y ago
  Generally grids try to average out to their target frequency over some period (24hrs, for example) because so many timekeeping systems rely on counting cycles. So sometimes they will run slightly above target and sometimes they will let it run slightly below target. Ordinary daily demand cycles help.

PeterisP 7y ago

A small frequency drop doesn't have a major impact to home users as well, but it's a symptom of a generation/consumption mismatch - the frequency dropping from 50 to 48.8 is a sign that the consumption is draining energy that's not generated by essentially taking it from the inertia of the major generators, and temporarily reducing consumption as all the large phase-linked motors are suddenly slowing down slightly... both of which are temporary, short-term, unsustainable effects. 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.

generatorguy 7y ago

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.