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. Bill Hawkins -----Original Message----- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jeremy Nichols 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 frequency. 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 data stream. Jeremy, N6WFO On Wed, Apr 5, 2017 at 2:12 PM, Bob kb8tq <kb...@n1k.org> wrote: > Hi > > 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 beeps. > 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. > > Bob > > > On Apr 5, 2017, at 3:05 PM, Hal Murray <hmur...@megapathdsl.net> wrote: > > > > > > preilley_...@comcast.net said: > >> When I installed power plants in the 1970's they has a special "clock" > that > >> 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 forward. > As > >> the operator observed the clock moving away from zero he would > >> reduce > the > >> 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. > > > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > > https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow > the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.