[time-nuts] 60Hz More or Less

[Eric Lemmon]

Ed,

Perhaps it is more important that the mains have long-term accuracy, rather
than short-term stability.  That is, there should not be any increasing
error in the time shown on an analog clock, and ideally it should never be
more than a few seconds slow or fast.  Major load shifts that cause grid
generation to fall behind should be corrected gradually.

I am reminded of the power generation plant on Johnston Island, where I
accumulated nearly three years of temporary duty back in the early 70's.
There were seven very large Diesel generators, and four were usually
operating in sync at any time.  In the control room, there were two analog
clocks- one was an electric clock that you might see in a classroom, and
next to it was a spring-wound marine chronometer.  Both clocks had large
dials and sweep second hands that could be seen from a distance.  The
chronometer was checked against WWVH every shift and wound at the same time
every day.  Due to its high quality, the chronometer seldom gained or lost
even a second, and it was hacked back to WWVH whenever it strayed.

I mention these details to illustrate that the power plant operator was
concerned not only that the generators were spinning at the correct speed to
produce exactly 60 Hz, but he also maintained zero accumulated error.  At
least once each hour, the operator would observe the relative positions of
the second hands of the two clocks.  If he saw that the electric clock was
lagging or leading the chronometer, he would move a knob to very slightly
increase or decrease the speed of the generators, until the second hands
were in alignment.  As a result, all of the electric clocks on the island
were always correct.  Of course, it is vastly more complex to accomplish the
same adjustment on a power grid that comprises a combination of fossil fuel,
nuclear, wind, and hydro power producers that are separated by hundreds of
miles.  The challenge becomes even more complex when the varying time
constants and reaction times are put into the mix.  Moreover, connecting the
Nation's power system into a gigantic grid is not necessarily a good thing.

73, Eric Lemmon WB6FLY

 
----- Original Message ----- 
From: "Ed Mersich" <wa6rzw at comcast.net>
To: <time-nuts at febo.com>
Sent: Sunday, April 01, 2012 3:18 PM
Subject: [time-nuts] 60Hz More or Less


> My Heathkit, and other AC clocks have been broken for months now. I
started
> a project to figure out how bad it was. It's getting interesting as I am
> approaching my goal of coding a software emulation of an AC line clock.
> During the process I developed a couple of web pages to help me understand
> the problem better. Frequency meter:
> http://wa6rzw.homelinux.net/addon/grid/gauge/hertz.html 
> 
> Grid history graph:
> http://wa6rzw.homelinux.net/addon/grid/graph/wgraph_1.html 
> 
> 
> 
> The meter requires a real HTML5 browser, anything but MSIE.  
> 
> 
> 
> When I started this my goal was to provide an external reference source to
> the Heathkit CG-1005, so that it will keep correct time.  Since I began I
> have considered a number of hardware solutions to correct or modify the
> Heathkit.  I think I am dragging my feet because there are no replacement
> clock chips (in case of disaster,) to be found for this model. At the
moment
> I am thinking about modifying a DC-AC inverter and syncing it to an audio
> oscillator, (don't laugh, my Heathkit 30 year old audio generator is way
> better, more stable, than the grid). 
> 
> 
> 
> 73, Ed - WA6RZW



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