[time-nuts] Re: One-night experiment: empirically verifying that the west coast power grid is actually interconnected

[Jeremy Elson]

>> Wow! I was not expecting the two curves to match up so well. What a
beautiful result!

>The effective impedances of the power grid are very low, so frequency
>discrepancies are almost physically impossible.

I should clarify my amazement (since I've gotten a couple of "of course
they match" messages).  It's not surprising that the power frequency is
synchronized, but it was surprising and delightful to be able to observe
this using a simple experiment from home on the first try. It's sort of
like the thrill of launching your own high altitude balloon and taking
pictures that show the curvature of the Earth and the dark of space: "of
course" the Earth is round and space is dark, but it's fun and educational
to be able to see it for yourself.

On Wed, Mar 9, 2022 at 12:42 AM Poul-Henning Kamp <phk at phk.freebsd.dk>
wrote:

> --------
> Jeremy Elson writes:
>
> > Wow! I was not expecting the two curves to match up so well. What a
> beautiful result!
>
> The effective impedances of the power grid are very low, so frequency
> discrepancies are almost physically impossible.
>
> If you want to see the real trouble, you need to GPS referenced high
> resolution phase measurements in two or more locations, and then
> plot the RMS of their differences.
>
> Traditionally the grid frequency has been stabilized by the inertia
> in the (huge!) rotors in centralized power plant's turbo generators.
>
> Solar power generation is instantaneous and contribute no inertia.
>
> Wind power has lots of small generators, but they are behind electronic
> "frequency converters", (AC->DC->AC conversion) which attenuates and
> delays the response from their generators inertia[1].
>
> With solar and wind taking over, for instance 60% of planned new
> generating capacity in USA next year will be solar and batteries,
> "low inertia situations" have become a real worry.
>
> The UK's grid collapse a couple of years ago is the first documented
> case where "low inertia" was "but for" factor.
>
> The big-iron-wound-with-copper manufacturers have started hawking
> "inertia generators" as a solution:  Huge spinning lumps of iron
> connected to a motor-generator.
>
> Other solutions are to mandate local battery-storage and inertia
> supplying control algorithems at large VE deployments.
>
> NREL has a good article called:
>
>         Inertia and the Power grid: A Guide without the Spin
>
>         https://www.nrel.gov/docs/fy20osti/73856.pdf
>
> Poul-Henning
>
> [1] Different control-algorithms in different wind generators on
> the same grid-radial could cause frequency oscillations, if the
> interactions are not taken into account.  This mandates quite
> conservative control strategies, which further attenuates the
> "inertia contributions".
>
> [2] https://www.eia.gov/todayinenergy/detail.php?id=51518
>
> --
> 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.
>