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posted by martyb on Tuesday March 06 2018, @10:12PM   Printer-friendly
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.


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  • (Score: 4, Interesting) by Geezer on Wednesday March 07 2018, @06:46AM (3 children)

    by Geezer (511) on Wednesday March 07 2018, @06:46AM (#648905)

    Not sure about the clock thing, but my gut feeling is that has it's roots as an inside engineer joke. Pretty sure utility companies don't give a rat's ass whether somebody has to adjust their clock once in awhile, but they do care about power factor coefficients on large inductive loads.

    I worked in old-school heavy industry for awhile, often with 4160/2300 systems, before solid-state VFD's came along, where we used big synchronous motors and monstrous autotransformers to keep things playing well together.

    I learned synchronization in the Navy, operating from two to six turbo-generators in a loop. It was a mark of uberness to be adept at manually paralleling the plant via a keen eye on a "synchroscope" and a deft hand on the bus tie breaker, with little to no frequency variation to freak out the electronics twidgets. Causing an outage (known to Navy snipes as "dropping the load") caused much hate and discontent.

    Fun times.

    https://en.wikipedia.org/wiki/Synchroscope [wikipedia.org]

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  • (Score: 3, Interesting) by Nuke on Wednesday March 07 2018, @11:33AM (2 children)

    by Nuke (3162) on Wednesday March 07 2018, @11:33AM (#648951)

    Pretty sure utility companies don't give a rat's ass whether somebody has to adjust their clock once in awhile

    In the UK they did, and my parents' house had several synchronous clocks. They were exact to the second (comparing with the Greenwich time signal which you could call on the phone). However the electricity companies announced about 25(?) years ago that they would cease to guarantee an average frequency as by then few people used such clocks.

    I did engineering watch keeping in the Navy at one time and in the engine control room there was both a propellor rpm indicator and a revolution counter. If the bridge had called for say 150 rpm we took a pride in getting the exact number of corresponding revolutions over a 4 hour shift.

    • (Score: 2) by RS3 on Wednesday March 07 2018, @03:05PM

      by RS3 (6367) on Wednesday March 07 2018, @03:05PM (#649004)

      Agreed- the good old days of quality for quality's sake are gone. I just did some more research and found postings from power company workers in most of the world's more developed countries, and 20 years ago they were saying they stopped caring about long-term frequency stability.

      Very stable quartz oscillators exist, and you can design devices such that the crystal is located in a fairly thermally stable area of the device. The associated oscillator circuitry can have a lot to do with phase noise, jitter, and long-term stability too.

      For very serious stability, crystal ovens https://en.wikipedia.org/wiki/Crystal_oven [wikipedia.org] exist. Not super cheap, but if you need it... https://www.mouser.com/Search/Refine.aspx?Keyword=crystal+oven&Ns=Pricing%7C0&FS=True [mouser.com]

      Now I'm feeling inspired to design an inexpensive but stable AC sine wave generator for keeping synchronous motor electric clocks on time. I could envision 1 master station that could even be tied to ntp, and simple slave stations that you'd plug your beautiful analog clocks into.

      Reminds me, I had read somewhere that more and more children can't read analog clocks.

    • (Score: 2) by Geezer on Wednesday March 07 2018, @08:42PM

      by Geezer (511) on Wednesday March 07 2018, @08:42PM (#649162)

      Propellers? That makes for an odd bit of trivia.

      On airplanes, Americans refer to propellers, or just props, while the Brits call them airscrews.

      Now flip that around. You say the RN calls the spinning bronze bits in the back propellers, but in the US Navy we called them screws. Go figure.

      At least I think a deck is still a deck...isn't it? LOL