[time-nuts] Daft idea with the National Grid

[Poul-Henning Kamp]

--------
Andy Talbot writes:

> Not sure what the time constant of the grid control is, but for* small
> signals* I doubt it can be faster than a few minutes.

There are generally spaking two time constants, the physical and the human.

The physical time constants are probably best understood as water in a
bucket:  If you kick it, complex ripples happen but eventually die out.

The timeconstant is generally order of five or ten cycles, unless you
make a short, those are much faster.

Mechanisms: Huge lumps of rotating iron, lots of switch-mode equipment
(including solar, wind mills and HVDC converters), magnetic hysteresis
in really big transformers, Maxwells/Telegraphers equations on long cables.

Unless the grid is on the verge of collapsing, the human time constant
is around 15 minutes.  Mechanism: People making mostly financial decisions.

As for your experiment, unless you use a psedurandom pattern, you stand
no chance of detecting a pattern.

I expect you may be able to show a bigger effect than you hypothesize
because the grid is not that "stiff".

Unless your house is right next to a big plant, there are five to ten
transformers between you and the power producer, and all of those "delay"
the phase in response to increasing load.

Your primary singal will therefore be phase-shift rather than frequency-
shift, which means your switching will have to be slow enough that
you can measure the difference between them.

PS: If you get friendly with people at grid control, they will send
you a copy of a pile of laplace equations from hell, which they use
to model the grid, and you can start by plugging your experiment
into them.  It wont be pretty.

-- 
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.