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Re:Why does the alarm clock snooze button give you nine extr... by X-Istence on Thursday October 31, 2013 @01:59AM (#6645488)
Equipment being out of phase has nothing to do with the timing. The timing of the 50/60 Hz signal actually changes throughout the day. On average the signal over 24 hours will equal about 24 hours so you can keep time with it, but as the load changes on the grid it will actually slow down and then speed back up when people turn off their devices at night.

The phases of the grid as a whole actually get synched up automatically. For example when they spin up a new turbine at a power plant if it is not within a certain percentage of the phase cycle it can actually cause massive amounts of damage as it gets pulled into the phase automatically.

The electric grid companies actually want to lower the current requirements for the 50/60 Hz cycle to be accurate in a 24 hour period to longer, such as possibly a week. This could mean that the clock in your oven for example may be a minute or two slow and slowly catch up over time as the grid has moments where it is clocked faster than 50/60 Hz.

For example see this graph of the last 60 minutes: http://www.nationalgrid.com/uk/Electricity/Data/Realtime/Fre... and here it is in real time for the whole US: http://fnetpublic.utk.edu/gradientmap.html

And here is the experiment that the power companies wanted to run/still are running regarding the relaxing of keeping the grid at 60 Hz: http://www.nbcnews.com/id/43532031/ns/technology_and_science...

Re:Why does the alarm clock snooze button give you nine extr... by cnvogel on Thursday October 31, 2013 @04:14AM (#6645717)
For reference, the specification for the European power grid is in the "Continental Europe Operation Handbook", Part "P1, Load-Frequency Control and Performance".

https://www.entsoe.eu/publications/system-operations-reports...

It's actually a pretty elaborate system (who would have guessed?) with phase-stiffness between subsystems specified, because this basically defines the amount of power drawn/sourced. Timing is just the "outermost" regulation loop.

Re:Why does the alarm clock snooze button give you nine extr... by gk1 on Thursday October 31, 2013 @02:45AM (#6645558)
> as the load changes on the grid it will actually slow down and then speed back up when people turn off their devices at night.

When I sailed on ships we knew not to use alarm clocks that plug into an outlet, because the load on the ship's generators is always changing, thus making plug-in alarm clocks less dependable than wrist watches.

Re:Why does the alarm clock snooze button give you nine extr... by X-Istence on Thursday October 31, 2013 @01:31PM (#6648229)
This is also the reason why a lot of clocks like that won't work on inverters that convert 12 VDC to 120 VAC since any load and most of them fall below spec.
Re:Why does the alarm clock snooze button give you nine extr... by epsylon on Thursday October 31, 2013 @12:26PM (#6647749)
> On average the signal over 24 hours will equal about 24 hours so you can keep time with it, but as the load changes on the grid it will actually slow down and then speed back up when people turn off their devices at night.

Yes, the load changes the frequency over the course of a day. In Great-Britain there's even a special peak after the afternoon TV shows finishes and people start turning on their electric kettles to prepare tea.

http://www.bbc.co.uk/britainfromabove/stories/people/teatime...

In fact, the exact frequency of the power grid can be used to identify precisely the time of the day!

http://en.wikipedia.org/wiki/Electrical_network_frequency_an...

Re:Why does the alarm clock snooze button give you nine extr... by X-Istence on Thursday October 31, 2013 @01:26PM (#6648178)
That is really cool that they can use it as a sort of fingerprint!