[time-nuts] Daft idea with the National Grid

[Andy Talbot]

The UK has a standalone frequency locked grid supply, nominal 50Hz, which
typically wanders +/- about 0.15Hz RMS over several minutes , with
occasional short-lived excursions out to 0.2 or 0.3Hz.  Average number of
cycles per period generally is normalised to 50Hz after a few days.
The typical loading for the country ranges over ~25GW to 45GW

Now, I wonder:
I can probably measure the grid frequency to a few micro Hz   over a period
of tens of seconds. So I make a continuous recording of this, averaged over
say 10 second periods.
Now take a 7kW load (the maximum reasonably possible on a domestic circuit)
and switch it on and off at intervals of perhaps 10 minutes, precisely
timed so it can be correlated with the frequency log.  That 7kW load will
be about 0.2ppm of the average for that for the whole of the UK.    By post
processing, and some deep correlation covering days worth of cycles of load
on-off with the frequency, I wonder if it would be possible to see the
loading, the mean frequency changing by a few uHz.
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 was a serious outage on 9 August 2019 that caused frequency to drop
below 49.5Hz and initiate automatic load shedding;   that happened over a
period of a couple of minutes but was a large scale problem.
https://www.ofgem.gov.uk/publications-and-updates/investigation-9-august-2019-power-outage

Andy
www.g4jnt.com