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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) by number11 on Wednesday March 07 2018, @12:30AM (1 child)
And it did exist, of course. That was what Edison built in the US (cue nasty PR battle between Edison as a DC proponent, and Westinghouse/Tesla as AC proponents). And there were places (parts of NYC, at least) that had DC until the mid-20th century. Cheap (tube) AC-DC radios were common ("All American Five", nasty things, chassis was hot to ground, filament voltages selected to work all in series at 115V).
One negative to DC: power switches must be much beefier. AC quenches the arc, but DC tries to keep it going.
(Score: 0) by Anonymous Coward on Wednesday March 07 2018, @01:00AM
I was in a warehouse building near Boston Chinatown in the late 1970s -- the freight elevator was DC. When the DC service finally ended around 1980, the building owner decommissioned that elevator (building no longer used for heavy freight.)