[time-nuts] Mains frequency

Hal Murray hmurray at megapathdsl.net
Wed Mar 12 15:23:48 EDT 2014

> So we know there are deviations in line freq. But it seems strange in this
> era of very accurate and inexpensive freq references. How much is related to
> the generation?

Controlling the line frequency is a giant PLL, with horrible complications.

The simple setup for a big generator is that if you add load, the generator 
will slow down slightly.  You can feed it more fuel to get it back up to 
speed.  I think that part is classic PLL theory.  Given the inertia of the 
generator and time delay around the loop, you can predict the response to a 
simple change in load, watch for instabilities and such.

In the real world, there are at least two levels of complications.  The first 
is that you are doing it with many generators rather than one.  When load is 
added, you have to decide which generator(s) will work harder.

The other nasty complication is that you want to do it as cheaply as possible 
as well as follow all the rules from regulators.

One of the complications from regulators is a requirement to make clocks that 
depend on the line frequency keep good time.  There was a proposal a while 
ago to remove that constraint.  I think it got dropped, but I could easily 
have missed an interesting announcement.


Has anybody collected data from a typical few-KW portable generator?  It 
would be interesting to see if "interesting" things happen if you turn some 
lights on/off at the right frequency.

Here is the Aurora video:
  Staged cyber attack reveals vulnerability in power grid 
(1 min)

These are my opinions.  I hate spam.

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