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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 DannyB on Wednesday March 07 2018, @04:53PM (2 children)
I was not aware of HVDC. My mention of transformers was in regard to high voltage AC transmission.
Yes, I understand we using switching power supplies. And maybe that is an effective way to step down your 200 or 350 VDC to a stable 12 V or 5 V for many common uses. Although real isolation from the the electrical outlet would desirable. So maybe a DC to DC converter as you say. But this introduces additional inefficiency.
All this talk of DC only would please Edison.
Tesla would be spinning in his grave. (which would generate an AC current.)
I'm a software guy. I don't remember which end of a soldering iron to pick up. So maybe I'm all wet (and grounded), but it occurs to me that what if you could have a 2-stage switching power supply. You switch the main 350 VDC to a capacitor, and as its charge reaches the "stage 1 voltage" (> 5VDC) you disconnect the main, then as capacitor discharges below "stage 1 voltage", it is re-connected to the 350 VDC power. Now during the period while this first stage capacitor is disconnected from the electrical line, it is then possible to connect it to a 2nd stage capacitor to keep it charged up to a stable 5V. This 2nd stage is another switching power supply. At no point in time is the 5V output ever electrically in contact with either of the 350 VDC input wires. There is probably some reason why this won't work or is impractical.
The lower I set my standards the more accomplishments I have.
(Score: 2) by Grishnakh on Wednesday March 07 2018, @06:43PM (1 child)
I was not aware of HVDC. My mention of transformers was in regard to high voltage AC transmission.
They've been using HVDC since the 1950s now. It's not new technology.
Yes, I understand we using switching power supplies. And maybe that is an effective way to step down your 200 or 350 VDC to a stable 12 V or 5 V for many common uses.
Maybe???? That's the ONLY way it's done now, powering any 12V or 5V (or less) system. Everything uses a switching supply now.
So maybe a DC to DC converter as you say. But this introduces additional inefficiency.
No, it doesn't (at least not any inefficiency that could be avoided in some other feasible way). Again, everything now uses a switching converter for stepping down 120VAC to whatever your small device uses. They wouldn't be doing this if it were inefficient. Efficiencies for these things are well into the 90% range. High-quality DC-DC converters are well over 95%.
At no point in time is the 5V output ever electrically in contact with either of the 350 VDC input wires.
Switching power supplies already do not have outputs electrically in direct contact with inputs, and many designs use transformers for galvanic isolation. Maybe you're thinking of those cheap little transformerless power supplies that you can implement with basically a diode and a couple capacitors. Really you should go look up switching power supplies and read about them before you talk any more, if you're worried about or interested in safety aspects, feasibility in modern power systems, etc. Wikipedia [wikipedia.org] has a decent article to start with, though it does look like it's a little dated in places to me.
(Score: 2) by DannyB on Wednesday March 07 2018, @09:29PM
What you say is interesting. I am clearly uninformed about switching power supplies. And HVDC.
The lower I set my standards the more accomplishments I have.