[time-nuts] Line Frequency standard change - Possible ?

Bob Camp kb8tq at n1k.org
Thu Feb 9 19:06:51 EST 2017


> On Feb 9, 2017, at 6:55 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> --------
> In message <CANX10hC=ayCN_hs8EdPCt0tK=SZmRS51pm2JXj+Aj_o5W390Eg at mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>> On 9 February 2017 at 21:31, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
>>> The only other possible "balance signal" is the voltage, and it
>>> suffers from a host of noise mechanisms, from bad contacts and
>>> lightning strikes to temperature, but worst of all, it takes double
>>> hit when you start big induction motors, thus oversignalling the
>>> power deficit.
>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>> I'm not sure what you mean by "balance signal" here.
> By "balance signal" I mean "which meter tells you if you need more
> or less power in the grid".
>> He said that he would
>> receive a call from the CEGB, saying they wanted X Watts, and a power
>> factor of Y.
> Exactly.
> Back when it was all rotating iron, they would only have
> asked for the "X Watts" and they would do so because the frequency
> was sagging, because that was the "balance signal" telling them
> that more power was getting used than produced (or vice versa).
> These days it has gotten much tricker, and I think getting into
> all the details may be stretching the patience here on time-nuts,
> but let me just give you two examples of how the consumption side
> has also made the job harder:
> It used to be that pretty much anything which drew power from the
> grid would be (give and take at bit of powerfactor) an ohmic loads.
> That means that if you sag the voltage, consumption drops (motors
> run slower, lamps are dimmer etc, and vice versa, high voltage would
> make consumption increase.  This was a beneficial feedback mechanism
> trying to keep the grid stable.
> These days almost anything, including computers, cars, washing
> machines and lightbulbs, have a switch-mode PSU which makes it a
> constant-power load.
> This means that if the grid voltage increases, current drops,
> reducing transport losses, which increases the voltage further.
> And vice versa.  This can make voltage regulation *much* harder.
> The other factor is batteries.  (This was first noticed during the
> rolling blackouts in California caused by Enrons market manipulations.)
> A city block would drop out at X kW, and usually when you cut it
> in again it would be Y% higher because all fridges and aircons would
> want to start.
> Thesedays when you cut in a cityblock it comes in at the same
> +Y%, and then about five seconds later all the chargers,
> in UPS, laptops, mobile phones and whats not, cuts in, and
> that can more than double the Y% and in some cases takes
> the grid right back out.
> Regulations have been proposed that it would make it illegal to
> change *any* battery if the frequency is below some set limit,
> in order to ensure that the grid can be relit faster and with
> less energy.

One simplistic way to look at all this is that a switcher presents a “negative
resistance” load. If you drop voltage, current goes up. OCXO’s happen 
to share this issue. Negative resistances are *not* what most power source
guys want in their control loop.


> So far no such regulation has been enacted, but everybody expects
> it to happen after the next big urban blackout.
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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