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from the you're-not-just-bored:-the-wall-clock-IS-slow dept.
Electric clocks on continental Europe that are steered by the frequency of the power system are running slow by up to 5 minutes since mid-January according to a news release from the European Network of Transmission System Operators for Electricity ('entsoe'). The transmission system operators (TSOs) will set up a compensation program to correct the time in the future.
Many electric clocks rely on the transmission system frequency to provide a source that minimises long-term drift. Quartz crystals have good short term stability, but dreadful long term stability, so plant and machinery that requires power to be turned on or off at a specific time each day without maintenance over a long period historically used clocks slaved to the power-system frequency, which is kept long-term stable by the system operators to prevent problems in power generation and transmission across national and supra-national grids - for example, attempting to switch supplies to generators that are not synchronised to the grid frequency can severely damage the generator.
It is normal for transmission system operators to allow the frequency to drop slightly at periods of high demand, thus slowing clocks, but usually, the frequency is increased during periods of low demand to ensure the long-term average frequency remains stable.
(Score: 2, Informative) by Anonymous Coward on Tuesday March 06 2018, @10:40PM (1 child)
Those giant spinning generators slow down under heavier loads and the line frequency is directly proportional to the rotation rate of the generators.
(Score: 5, Informative) by Nuke on Wednesday March 07 2018, @11:49AM
Former power station engineer here. No they do not generally slow down. More power is applied to them (like opening the trhottle valves more, leading to burning fuel faster) to keep the speed up. It that is not sufficient, in the UK at least more power stations are switched in (old coal and oil burners kept in reserve, some actually kept spinning at idle power, and gas turbine stations). If even that is not enough the grid controllers start shedding load (ie some areas get power cuts). If the overload is long term, voltage might be reduced, but frequency is always maintained; for one thing the steam turbines used in some power stations hit resonant vibration frequencies at lower than design speed, and with a national grid everthing runs at the same speed.
I am talking about the UK where almost the entire country (except Northern Ireland) is wired together with the National Grid. I understand that some countries with poorer systems and small local networks can have "brownouts". I don't think the UK grid has reduced voltage since the 1980's coal miners' strike, and I have never seen a dynamic brownout; but I expect there will be more in future now there is a fashion to move back to localisation.