[time-nuts] Line Frequeny Stablity
bill.iaxs at pobox.com
Thu Apr 6 00:59:07 EDT 2017
Perhaps I should have clarified that while the synchronous machines all
run at the same frequency, that frequency depends on the balance of
steam (or hydraulic) power to the turbines that spin the generators and
the aggregate power demand. When the power is not balanced, the
frequency of the coupled system will change, but very slowly in
proportion to the size of the network of generators.
I don't know the effects of the DC tieline inverter, which can run at
any set frequency, but any difference in frequency has to affect the
power out of or into the tie line.
As to doing the clock adjustment around quitting time at 5 PM, my
experience is different. A system that took a frequency input and showed
it as a function of time revealed that the frequency sagged during the
workday and the air conditioning day, but was increased to make up the
lost cycles during the minimum load time around 4:30 AM.
In 1955 or so, The Air Force determined that the time of minimum human
activity (and hence the maximum probability of attack) was at 4:30 in
the morning. Independent research with traffic counters revealed a sharp
dip in traffic at that time of day. Adjusting the cycle count at the
time of minimum activity also minimized the cost of making that
adjustment. Sorry, I have no recent data, but it sure feels lonely to be
up at 4:30 AM.
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Jeremy
Sent: Wednesday, April 05, 2017 6:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Line Frequeny Stablity
A fun way to monitor the state of the grid is to watch the web site of
the Power Information Technology Laboratory <http://powerit.utk.edu> at
the University of Tennessee <http://www.utk.edu>, Their site lists in
both tabular and graphical (map) form the frequency of the grid. Most of
it is USA-based but there are a few other countries also monitored.
I have one of the monitors (in the table display page <
http://fnetpublic.utk.edu/tabledisplay.html> my monitor is #853 in the
Western Interconnection-I'm in California).
The monitors, about the size of a thick hardback book, plug into a
convenient AC line outlet, connect to your Internet router, and have a
small puck-style GPS antenna so that it knows the time and where it is.
The unit has an LCD display of date, time, line voltage, and line
The voltage is shown to 3 decimal digits of resolution and the frequency
to four digits.
I got my monitor from the U of T after I sent them a report on my
home-made monitor's results. It's interesting to watch the frequency
wander up and down but always average very close to 60.000 Hz. They saw
I had an interest and offered me one of their toys. The only thing it
doesn't do is connect to my PC so I can monitor it long-term. I suppose
if I were clever with network stuff there'd be a way to tap into its
On Wed, Apr 5, 2017 at 2:12 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> Back in high school, one of the radio club members figured out that
> the "clock adjustment" took place locally between 4:30 and 5:00 PM.
> Needless to say, pretty much everybody spent the next week listening
> to WWV and watching the clock's second hand go out of sync with the
> This was back in the late 1960's
> and the idea of a grid was a bit looser than it is today. Indeed it
> was post 1964 so there *were* grids big enough to take out the whole
> north east section of the US. Since we were very much in that area the
> topic of grid sync came up. Nobody ever really had a good answer to
> that question. That included the guys who ran the local power company.
> > On Apr 5, 2017, at 3:05 PM, Hal Murray <hmurray at megapathdsl.net>
> > preilley_454 at comcast.net said:
> >> When I installed power plants in the 1970's they has a special
> >> showed the cumulative error in terms of clock time.
> > How big were the grids back then?
> > What was the typical range of error over a day or month?
> >> If the generator ran a little too fast the clock would move
> >> the operator observed the clock moving away from zero he would
> >> reduce
> >> plant's power and the clock would move backward toward zero. ...
> > Does that operator control a single generator or a whole grid?
> > Does having a human in the loop help the control loop stability?
> > --
> > These are my opinions. I hate spam.
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