Re: [time-nuts] Features of a Precision Clock?
Although I have nothing to add to the discussion, I want to say that I too found it fascinating. I became interested in AC power grid systems through the exploration of several abandoned power plants and have been doing a lot of reading recently into their theoretical and operational details. It was very nice to read this discussion coming from people who actually know what they're talking about as compared to my relatively uninformed speculation :). Finally, if anyone would like to take care of some of the mistakes and inaccuracies in the 'synchroscope' article I wrote on Wikipedia some time back, you're more than welcome to do so :). It could certainly use the attention and it sounds like there are many people here more than capable of doing so. http://en.wikipedia.org/wiki/Synchroscope Cheers, Rusty On 10/8/06, JayHolovacs [EMAIL PROTECTED] wrote: I have found this utterly fascinating.I've learned a great deal from this exchange. Jay ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
i guess i have to add my thanks to the list also, where else could i find this info and from people who are in the business. thanks tom[EMAIL PROTECTED] - Original Message - From: JayHolovacs [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, October 08, 2006 6:49 PM Subject: Re: [time-nuts] Features of a Precision Clock? I have found this utterly fascinating.I've learned a great deal from this exchange. Jay Bill Hawkins wrote: O Since control is not precise, the subject is probably off topic for this list. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
In message [EMAIL PROTECTED], Bill Hawkins writes: Think of the incredible amount of energy stored in many rotating generators linked by the synchronous network. This is actually far less than you seem to think. If the load suddenly increased 10% [...] Then all generators would trip and disconnect from the grid. No reasonably sized turbine driven generator survives a 10% load jump without exensive repairs. Your explanation was true about 30 years ago, not so any more. After deregulation, electrical grids run very close to the edge because nobody makes money on the reserve capacity and therefore everybody only produces exactly what they are legally required to. The main reason for all the research into UTC locked grids is that it would prevent produces from cheating at the scale. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Poul-Henning Kamp wrote: In message [EMAIL PROTECTED], Bill Hawkins writes: Think of the incredible amount of energy stored in many rotating generators linked by the synchronous network. This is actually far less than you seem to think. If the load suddenly increased 10% [...] Then all generators would trip and disconnect from the grid. No reasonably sized turbine driven generator survives a 10% load jump without exensive repairs. Your explanation was true about 30 years ago, not so any more. After deregulation, electrical grids run very close to the edge because nobody makes money on the reserve capacity and therefore everybody only produces exactly what they are legally required to. The main reason for all the research into UTC locked grids is that it would prevent produces from cheating at the scale. Whilst it may be reasonable to run close to the edge in large grids where no one generator provides a large proportion of the power, it is not so for smaller grids with a few generators providing a large proportion of the power. In the local (NZ) market generators are paid to supply spinning reserve capacity. Since we only have 2 separate AC distribution systems connected by a bidirectional dc link and one operator coordinates the distribution from all the generators cheating at the scale isn't likely. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Well, 10% is extreme, but in the NE USA it is possible to do that by losing one tie line. During the NE blackout on Nov 9, 1965, less than 10% fell off the line. The remaining generators slowed down and tripped under-frequency relays at about 57 Hz or tripped overload breakers. This split the network into islands in about 4 seconds. The resulting instability took out most of the remaining generators inside 5 minutes. See http://www.cmpco.com/about/system/blackout.html Please do not discredit all of my explanations by saying they are old. The control engineer that I talked to in 2002 worked in a 2,400 megawatt coal-fired plant built in the 70's. Many of the US plants are that old. Also, Newton's F=MA and Ohm's law are much older, but still quite valid (for large numbers of atoms). Similarly, the laws of control and stability still apply to mechanical systems. The governor for a hydroelectric turbine operates the same as the governor for a steam turbine. There can only be one integrating controller for a coupled network to be stable. The fuel incremental cost for atomic energy is a lot cheaper than the cost of coal, oil or gas. Power dispatchers also hold down costs by assigning extra load to stations in order of fuel cost. Producers bill for megawatt-hours delivered to the grid. This introduces the element of time. It is tempting to use extremely accurate time, but the measurement of watts is not much better than 0.1%. The bean counters will tell you that 0.1% of a US billion dollars is a million dollars. They would like to be accurate to the penny. Is this the cheating at the scale problem that you mentioned? Regards, Bill Hawkins Never attribute to malice what can adequately be explained by the limitations of a three pound brain. Ah, unless the person is known to be a psychopath with a damaged brain. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Poul-Henning Kamp Sent: Sunday, October 08, 2006 1:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Features of a Precision Clock? In message [EMAIL PROTECTED], Bill Hawkins writes: Think of the incredible amount of energy stored in many rotating generators linked by the synchronous network. This is actually far less than you seem to think. If the load suddenly increased 10% [...] Then all generators would trip and disconnect from the grid. No reasonably sized turbine driven generator survives a 10% load jump without exensive repairs. Your explanation was true about 30 years ago, not so any more. After deregulation, electrical grids run very close to the edge because nobody makes money on the reserve capacity and therefore everybody only produces exactly what they are legally required to. The main reason for all the research into UTC locked grids is that it would prevent produces from cheating at the scale. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
In message [EMAIL PROTECTED], Bill Hawkins writes: Please do not discredit all of my explanations by saying they are old. The control engineer that I talked to in 2002 worked in a 2,400 megawatt coal-fired plant built in the 70's. Many of the US plants are that old. The hardware may be old, but the control strategy is new. Most regulating entities have updated their modus operandi after the big blackouts we have seen in the last couple of years. In particular, most places the frequency tolerance have been increased, both in frequency and duration. Active research in this area is for the net to fall apart into self-sustaining 'cells' but nobody has even dared suggest a live test of this concept yet. But since nobody has any better ideas, they keep trying to make it look plausible somehow. The major trouble in this area is that they never get to run a live test so nobody knows what works until it (usually) is too late. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
OK, I think the important things to know for people on this list are the following: 1. A power grid has no natural frequency. 2. The rate of change of frequency for small changes is determined by the unbalance between generated power and the amount of load demand. This is because the grid can't store much energy, not the way a water tower can store water. 3. It is the actions of those people or automation programs that apportion load to generation plants that sets a mean frequency, by using spare capacity at night to catch up. Since control is not precise, the subject is probably off topic for this list. Regards, Bill Hawkins ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
In message [EMAIL PROTECTED], Bill Hawkins writes: Since control is not precise, the subject is probably off topic for this list. It all depends on your integration time. I was told from Stockholm that they hadn't lost track of a single cycle in 50 some years, so that's: 20msec / 50 y = 12.675e-12 As far as I know, no other frequency reference can do that. Obviously the numbers are highly suspect, because he didn't know what they measured against... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
From: Poul-Henning Kamp [EMAIL PROTECTED] Subject: Re: [time-nuts] Features of a Precision Clock? Date: Sun, 08 Oct 2006 21:12:16 + Message-ID: [EMAIL PROTECTED] In message [EMAIL PROTECTED], Bill Hawkins writes: Since control is not precise, the subject is probably off topic for this list. It all depends on your integration time. I was told from Stockholm that they hadn't lost track of a single cycle in 50 some years, so that's: 20msec / 50 y = 12.675e-12 You rarely need that kind of stability for tau = 50Y. As far as I know, no other frequency reference can do that. Obviously the numbers are highly suspect, because he didn't know what they measured against... Not counting the times we have been WITHOUT cycles at all I assume? We had a large outage in the 80thies. I remember it clearly as I just came out of the subway when it all shut down. I don't think they run high in frequency to come back cycle-wise, do you? Outage isn't common, even if my office have experienced it a little too often, and certain other areas (Kista) also have experienced it my home have been spared most of the times. The Kista incidents have been the result of lack of redundancy, which is a bit annoying since it is such an IT-industry concentrated place. Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Hi guys, power grids are very large, consider for example the continental US or Europe, grids can probably extend 1000km's easily. At the speed of light, that's 3ms transition time! Electric current travels much slower than that so the time for a wave to propagate from Berlin to Marsielle is probably more like 10ms or so. Impressive how they keep it all in sync. Bye, Said ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
The electric grid is all a myth Below is the truth. (Presented for your comical enjoyment) ** ** DARK CONSPIRACY INVOLVING ELECTRICAL POWER COMPANIES SURFACES Rewritten by the Quantum Mechanic (Author Unknown) Updated 8/7/88 W0PN ** ** For years the electrical utility companies have led the public to believe they were in business to supply electricity to the consumer, a service for which they charge a substantial rate. The recent accidental acquisition of secret records from a well known power company has led to a massive research campaign which positively explodes several myths and exposes the massive hoax which has been perpetrated upon the public by the power companies. The most common hoax promoted the false concept that light bulbs emitted light; in actuality, these 'light' bulbs actually absorb DARK which is then transported back to the power generation stations via wire networks. A more descriptive name has now been coined; the new scientific name for the device is DARKSUCKER. This newsletter introduces a brief synopsis of the darksucker theory, which proves the existence of dark and establishes the fact that dark has great mass, and further, that dark particle (the anti-photon) is the fastest known particle in the universe. Apparently, even the celebrated Dr. Albert Einstein did not suspect the truth.. that just as COLD is the absence of HEAT, LIGHT is actually the ABSENCE of DARK... scientists have now proven that light does not really exist! The basis of the darksucker theory is that electric light bulbs suck dark. Take for example, the darksuckers in the room where you are right now. There is much less dark right next to the darksuckers than there is elsewhere, demonstrating their limited range. The larger the darksucker, the greater its capacity to suck dark. Darksuckers in a parking lot or on a football field have a much greater capacity than the ones in used in the home, for example. It may come as a surprise to learn that darksuckers also operate on a celestial scale; witness the Sun. Our Sun makes use of dense dark, sucking it in from all the planets and intervening dark space. Naturally, the Sun is better able to suck dark from the planets which are situated closer to it, thus explaining why those planets appear brighter than do those which are far distant from the Sun. Occasionally, the Sun actually over sucks; under those conditions, dark spots appear on the surface of the Sun. Scientists have long studied these 'sunspots' and are only recently beginning to realize that the dark spots represent leaks of high pressure dark because the Sun has over sucked dark to such an extent that some dark actually leaks back into space. This leakage of high pressure dark frequently causes problems with radio communications here on Earth due to collisions between the dark particles as they stream out into space at high velocity via the black 'holes' in the surface of the Sun. As with all manmade devices, darksuckers have a finite lifetime caused by the fact that they are not 100% efficient at transmitting collected dark back to the power company via the wires from your home, causing dark to build up slowly within the device. Once they are full of accumulated dark, they can no longer suck. This condition can be observed by looking for the black spot on a full darksucker when it has reached maximum capacity of untransmitted dark... you have surely noticed that dark completely surrounds a full darksucker because it no longer has the capacity to suck any dark at all. A candle is a primitive darksucker. A new candle has a white wick. You will notice that after the first use the wick turns black, representing all the dark which has been sucked into it. If you hold a pencil next to the wick of an operating candle, the tip will turn black because it got in the way of the dark flowing into the candle. It is of no use to plug a candle into an electrical outlet; it can only collect dark.. it has no transmission capabilities. Unfortunately, these primitive darksuckers have a very limited range and are hazardous to operate because of the intense heat produced. There are also portable darksuckers called flashlights. The bulbs in these devices collect dark which is passed to a dark storage unit called a battery. When the dark storage unit is full, it must be either emptied (a process called 'recharging') or replaced before the portable darksucker can continue to operate. If you break open a battery, you will find dense black dark inside, evidence that it is actually a compact dark
Re: [time-nuts] Features of a Precision Clock?
I have found this utterly fascinating.I've learned a great deal from this exchange. Jay Bill Hawkins wrote: O Since control is not precise, the subject is probably off topic for this list. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Over that time period, maybe a calendar :-) Didier Poul-Henning Kamp wrote: In message [EMAIL PROTECTED], Bill Hawkins writes: Since control is not precise, the subject is probably off topic for this list. It all depends on your integration time. I was told from Stockholm that they hadn't lost track of a single cycle in 50 some years, so that's: 20msec / 50 y = 12.675e-12 As far as I know, no other frequency reference can do that. Obviously the numbers are highly suspect, because he didn't know what they measured against... ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Hi there, Having worked with the folks who operate the power utilities (I designed protective relaying and recorder electronics for several years), I can advise that they do take the long-term accuracy of their power seriously. However, the short-term is not a big concern, and in fact, they cannot control it all that well. It turns out that power flow on an AC line requires a phase difference between end points (as opposed to a DC system where it is resistance that counts). The resistance of the line is not important. This is because power transmission lines are almost pure inductive reactance - in power systems terms, the line angle (impedance angle) is generally near to 90 degrees. Systems are connected at multiple points, like a mesh of rubber bands connecting weights and support points. Some of these points are heavier (down) or pull stronger (up), some have stronger bands, some have very weak bands. When the load changes, or when a line opens or closes, the phase angles of the power through all these interconnected ties will shift to establish a new equilibrium. In so doing, your power will advance or retard somewhat. If you have a clock running on the phase of AC power, your clock will gain or lose a bit of time. It is unclear whether you will ever be corrected - the new equilibrium might just be a fact of life. The prime movers of the systems (generators) are almost all physical moving devices, like hydro-electric (water dams) or thermal (coal, natural gas, or nuclear powered turbines). When they are loaded down, they slow down - and when less loaded, they speed up. This isn't as bad as it sounds - the rest of the system rolls along at the system frequency, and the generator's slight frequency change actually becomes a phase change, which, as per above, changes its power output. Then the generator gets back into sync, but with a phase angle different than before. As you can imagine, it is a challenge to maintain tight control of the phase, with all the changing conditions on the power grid. In the case of our utility (Manitoba Hydro), they keep power system clocks at the big 24 by 7 staffed power stations and in the main control room, and will, under their rules of operation, tweak things slightly over time. I am not certain of the rules of operation, or of the way they tweak things (generator bias?), but could find out from friends and colleagues, if you wish. Here in Manitoba, we are blessed to have much of our power supplied from the hydro-electric generators in the north, through a DC link. It turns out that this is economical above a certain distance and power level - related partly to the skin effect (yes it becomes important, even at 60 Hz). At the south end of the link, we have a DC-to-AC inverter system (huge - pretty impressive), fibre optic fired thyristors (equivalent to triacs? SCRs?). We can change the firing angle on a cycle-by-cycle basis, adjusting the power flow in and out, and exerting extraordinary control of the system phase. We use it to stabilize the system more than for power frequency correction, but I assume that this could be done too, just unsure of the algorithm. Of course, the system is a lot more complex than I describe it here, with phase shifting transformers, tap changers, and more modern back-to-back DC links, wind generation at the distribution (lower voltage) level, etc. More complex than I understand, to be sure. But those are the basics. Regards, Dean Weiten, Elecsys Solutions, Winnipeg, Manitoba. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Dean, Thank you so much for your detailed and authoritative note about power utilities. I am not certain of the rules of operation, or of the way they tweak things (generator bias?), but could find out from friends and colleagues, if you wish. If it wouldn't be too much to ask, yes, I think several of us would be interested in how, and under what rules, they tweak the frequency. My look at 60 Hz here in the US suggests there are short-term (on the order of hours and days) changes for power flow as you desribed, but also long-term forces that tend to maintain semi-accurate time in spite of the short-term variations. Surprisingly, here in Washington at least, a mains clock is accurate to a few seconds a month, even if on a day to day basis it varies up to 10 seconds. http://www.leapsecond.com/pages/mains/ /tvb ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock - Grid
Does anybody in this group look at power line frequency drift? Somebody once told me that they tried to get frequency info from the Palo Alto utilities. When they finally got through to somebody who knew what was going on, the answer was We aren't tariffed for that. Does anybody have a URL for the frequency specs? (US or California.) I'm also interested in the voltage specs. I poked around on google a while ago but didn't find anything interesting. For the UK grid there's info at : http://www.nationalgrid.com/uk/Electricity/Data/Realtime/ Which contains real time frequency data for the last 60 minutes. it also says: Quote Frequency The normal system frequency is 50Hz. As electricity cannot be stored, the instantaneous generation must match the demand being taken from the system. If the instantaneous demand is higher than the generation, the system frequency will fall. Conversely, if the instantaneous generation is higher than the demand, the frequency will rise. System frequency will therefore vary around the 50 Hz target and National Grid has statutory obligations to maintain the frequency within +/- 0.5Hz around this level. However, National Grid normally operates within more stringent 'operational limits' which are set at +/- 0.2Hz. /Quote Roj ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Tom Van Baak wrote, If it wouldn't be too much to ask, yes, I think several of us would be interested in how, and under what rules, they tweak the frequency. It helps to have a mechanical understanding of the problem. By the time you get to the end of this, you should know why the frequency can't be continuously regulated. If you deliver steam to a turbine from a large boiler, the speed of the turbine is limited by the rate of steam flow and the pressure drop across the turbine. Flow times drop gives you the power from the boiler to the turbine, just like amps times volts. A throttling valve is put in the steam line to regulate the power to the turbine. The turbine will rotate at a speed determined by the power balance between the steam and the shaft load. Increase the load and the turbine slows down. The load is a synchronous generator. This doesn't mean much for an isolated turbine and generator combination. If you connect thousands of generators to a common distribution system, they are all locked together in speed, but not phase angle. As Dean said, the phase angle varies with the power flow. The frequency varies with the power balance. To emphasize the common speed aspect of the power system, if one generator is disconnected from the system (perhaps because its hydrogen cooling gas has developed a leak) then it must be re-connected very carefully. The steam throttle is adjusted to bring the speed of the generator (and its frequency) up to match the distribution network frequency. Then a phase indicator is used to detect the phase angle difference. The breaker connecting the generator to the power system can be closed when the phase angle is zero. If the angle is not zero, the power of thousands of generators tries to bring the one generator into phase alignment instantly. The mechanical forces can do great damage before the breaker trips. So here we have this network of thousands of turbines and generators all locked to the same frequency because they are synchronous machines. In effect, we are back to the simple case of the speed being determined by the power balance between steam and electrical load. But we really have a network, and the ability to measure power flows at various points in the network. Electric utilities have joint power dispatching centers. The dispatchers work to balance the power in the system by telling power generation stations how much power to generate. This works in large scale systems. You can't tell the users how much to consume, you just try to meet the demand. Small generating plants and large networks maintain a clock attached to the power line and another from a standard, like WWV before GPS. The station manager adjusts the fuel flow to the boilers to alter the power balance to change the turbine speed. The throttling valve can't be adjusted with sufficient precision to do frequency control. Large or small, the power line clock loses time when there isn't quite enough fuel and gains when there's a bit too much. Large networks barely stay ahead of demand with new power plants. There are peaking plants that only generate when the demand exceeds the base capability of the boilers. They use expensive fuel for rapid response (gas turbines) but they hold the power balance. If you measure the difference between power line time and GPS time over 24 hours, you will see the line clock lose time during the day, when loads are highest, and regain that lost time in the very early morning, when loads are low. The dispatchers tell generating stations to add a bit more fuel to bring the line clock back to match GPS or a little ahead, anticipating the day's demand. Why not use automatic frequency control? Because the controllers in the different stations would fight each other, because they are tied together by the synchronous network. In other words, it is not possible to regulate a stable speed/frequency with more than one integrating controller - and one controller can't regulate enough power to stabilize the network - unless the controller is a dispatcher able to tell many stations what to do. More than I intended to say, but I hope someone finds it useful. None of the above is guesswork. I've been interested in this since a summer job on an island in 1955. I've not talked to a dispatcher, but I have confirmed the details with a control engineer at a large power station. Regards, Bill Hawkins ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock - Grid
Thanks, Roj The data from the UK grid show the daily cycle of loads in the 8 day chart. Minimum load is about 4 AM. Back in the 50's we were told that the time of minimum human activity was 4:30 AM, so that's when we could expect an atomic bomb attack. Too bad they didn't plot the delta time (integrated frequency) for 24 hours. Regards, Bill Hawkins -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Roger Glover Sent: Saturday, October 07, 2006 2:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Features of a Precision Clock - Grid Does anybody in this group look at power line frequency drift? Somebody once told me that they tried to get frequency info from the Palo Alto utilities. When they finally got through to somebody who knew what was going on, the answer was We aren't tariffed for that. Does anybody have a URL for the frequency specs? (US or California.) I'm also interested in the voltage specs. I poked around on google a while ago but didn't find anything interesting. For the UK grid there's info at : http://www.nationalgrid.com/uk/Electricity/Data/Realtime/ Which contains real time frequency data for the last 60 minutes. it also says: Quote Frequency The normal system frequency is 50Hz. As electricity cannot be stored, the instantaneous generation must match the demand being taken from the system. If the instantaneous demand is higher than the generation, the system frequency will fall. Conversely, if the instantaneous generation is higher than the demand, the frequency will rise. System frequency will therefore vary around the 50 Hz target and National Grid has statutory obligations to maintain the frequency within +/- 0.5Hz around this level. However, National Grid normally operates within more stringent 'operational limits' which are set at +/- 0.2Hz. /Quote Roj ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock - Grid
Does anybody have a URL for the frequency specs? (US or California.) Already people have said there are no guarantees, but my experience: instantaneous frequency might go up and down one or two tenths of a percent for periods of time of minutes to tens of minutes and sometimes (but not often) hours. Over a whole day, they seem to try to average it out and it was rare (over my measurements) for a 60Hz wallclock to lose or gain more than a few seconds a day. My frequency measurements were done with a long-period frequency counters, crystal timebase good to a few ppm, and time measurements was comparing the wall clock to WWV. In other words, not very high-tech by the measurement standards of many here! Tim. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Dean Weiten wrote: Hi there, Having worked with the folks who operate the power utilities (I designed protective relaying and recorder electronics for several years), I can advise that they do take the long-term accuracy of their power seriously. However, the short-term is not a big concern, and in fact, they cannot control it all that well. It turns out that power flow on an AC line requires a phase difference between end points (as opposed to a DC system where it is resistance that counts). The resistance of the line is not important. This is because power transmission lines are almost pure inductive reactance - in power systems terms, the line angle (impedance angle) is generally near to 90 degrees. Systems are connected at multiple points, like a mesh of rubber bands connecting weights and support points. Some of these points are heavier (down) or pull stronger (up), some have stronger bands, some have very weak bands. When the load changes, or when a line opens or closes, the phase angles of the power through all these interconnected ties will shift to establish a new equilibrium. In so doing, your power will advance or retard somewhat. If you have a clock running on the phase of AC power, your clock will gain or lose a bit of time. It is unclear whether you will ever be corrected - the new equilibrium might just be a fact of life. The prime movers of the systems (generators) are almost all physical moving devices, like hydro-electric (water dams) or thermal (coal, natural gas, or nuclear powered turbines). When they are loaded down, they slow down - and when less loaded, they speed up. This isn't as bad as it sounds - the rest of the system rolls along at the system frequency, and the generator's slight frequency change actually becomes a phase change, which, as per above, changes its power output. Then the generator gets back into sync, but with a phase angle different than before. As you can imagine, it is a challenge to maintain tight control of the phase, with all the changing conditions on the power grid. In the case of our utility (Manitoba Hydro), they keep power system clocks at the big 24 by 7 staffed power stations and in the main control room, and will, under their rules of operation, tweak things slightly over time. I am not certain of the rules of operation, or of the way they tweak things (generator bias?), but could find out from friends and colleagues, if you wish. Here in Manitoba, we are blessed to have much of our power supplied from the hydro-electric generators in the north, through a DC link. It turns out that this is economical above a certain distance and power level - related partly to the skin effect (yes it becomes important, even at 60 Hz). At the south end of the link, we have a DC-to-AC inverter system (huge - pretty impressive), fibre optic fired thyristors (equivalent to triacs? SCRs?). We can change the firing angle on a cycle-by-cycle basis, adjusting the power flow in and out, and exerting extraordinary control of the system phase. We use it to stabilize the system more than for power frequency correction, but I assume that this could be done too, just unsure of the algorithm. Of course, the system is a lot more complex than I describe it here, with phase shifting transformers, tap changers, and more modern back-to-back DC links, wind generation at the distribution (lower voltage) level, etc. More complex than I understand, to be sure. But those are the basics. Regards, Dean Weiten, Elecsys Solutions, Winnipeg, Manitoba. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts When the length of the transmission line approaches a quarter wavelength at the power line frequency (1250 km/780 miles @ 60Hz) it acts somewhat like an open wire RF transmission line. The line no longer acts like a lumped component and it also acts like a somewhat inefficient antenna radiating at the grid frequency. Some generators are kept continuously spinning and synchronised to the mains but generating little power. These spinning reserve generators are necessary to stabilise the grid against load fluctuations, they can very quickly supply power when required. Here in New Zealand where the length of each of the 2 main islands approaches a quarter at the 50Hz grid frequency a submarine bidirectional dc link connects the power systems of the 2 islands. Both mercury vapour phase controlled rectifier and SCR inverters are used. A thyristor is another name for an SCR, triacs are not used in high power circuits, inverse parallel SCRs are used where a triac like function is required. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Dr Bruce Griffiths said, Some generators are kept continuously spinning and synchronised to the mains but generating little power. These spinning reserve generators are necessary to stabilise the grid against load fluctuations, they can very quickly supply power when required. I hope you don't mean that the reserve generators supply power from their rotational inertia. They do, but not enough to keep the frequency from changing. There's another reason for wasting heat. Spinning reserve is necessary because it takes hours to bring a big turbine up from a cold start. They have to heat up slowly to avoid thermal stress in the blades and the big metal bits. The boiler also has to be hot, but even so it can't change quickly. Quickly means minutes, not milliseconds. Think of the incredible amount of energy stored in many rotating generators linked by the synchronous network. If the load suddenly increased 10% then the rotational energy removed from the generators would supply the increased demand at the cost of slowing down. Then turbine governors open steam valves, causing the boiler pressure to drop, causing more fuel and water to be added to the boiler. The network gradually comes back up to speed until the turbine governors are satisfied, which is not exactly 50/60 cycles. In fact, this group is liable to lose interest (if any) in power line frequency when it becomes clear that the system has no natural frequency. It is not an oscillator whose frequency is determined by physical properties, like a piezoelectric crystal or a cloud of atoms. What you are seeing in the power line frequency is a marvel of coordinated control systems barely restraining enormous energies. Since I'm in the control business, I think that's neat. YMMV. Regards, Bill Hawkins ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Bill Hawkins wrote: Dr Bruce Griffiths said, Some generators are kept continuously spinning and synchronised to the mains but generating little power. These spinning reserve generators are necessary to stabilise the grid against load fluctuations, they can very quickly supply power when required. I hope you don't mean that the reserve generators supply power from their rotational inertia. They do, but not enough to keep the frequency from changing. There's another reason for wasting heat. Spinning reserve is necessary because it takes hours to bring a big turbine up from a cold start. They have to heat up slowly to avoid thermal stress in the blades and the big metal bits. The boiler also has to be hot, but even so it can't change quickly. Quickly means minutes, not milliseconds. Think of the incredible amount of energy stored in many rotating generators linked by the synchronous network. If the load suddenly increased 10% then the rotational energy removed from the generators would supply the increased demand at the cost of slowing down. Then turbine governors open steam valves, causing the boiler pressure to drop, causing more fuel and water to be added to the boiler. The network gradually comes back up to speed until the turbine governors are satisfied, which is not exactly 50/60 cycles. In fact, this group is liable to lose interest (if any) in power line frequency when it becomes clear that the system has no natural frequency. It is not an oscillator whose frequency is determined by physical properties, like a piezoelectric crystal or a cloud of atoms. What you are seeing in the power line frequency is a marvel of coordinated control systems barely restraining enormous energies. Since I'm in the control business, I think that's neat. YMMV. Regards, Bill Hawkins ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts In NZ power generation is predominantly hydro with some thermal generation and small amounts of wind generation. Consequently response to load fluctuations can be somewhat faster than when purely thermal generation is used. The frequency is usually held between 49.9 and 50.1 Hz. However when generating capacity is lost the frequency will drop well below 49.9Hz. Operation for more than a few seconds below 95% of design frequency can severely damage some modern thermal generating plant. Another reason for avoiding very long AC transmission lines is the reactive current flowing in the cable shunt capacitance may exceed the load current, especially in non air insulated cables,. this reactive power increases the resistive losses in the cable. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Bill Hawkins said (among other interesting stuff) Why not use automatic frequency control? Because the controllers in the different stations would fight each other, because they are tied together by the synchronous network. In other words, it is not possible to regulate a stable speed/frequency with more than one integrating controller - and one controller can't regulate enough power to stabilize the network - unless the controller is a dispatcher able to tell many stations what to do. I posted brief details here last year (22/8/05) of just such a system that was tried here in NZ some time ago - to reiterate the relevant text *** I have here the remains of an attempt in the early seventies to bring this type of system up to date - it comprised an HP 105 series quartz reference, a K20 - HP 5280A up down counter and an HP 5321B clock. The up down counter was driven from 100 Hz signals derived from both the 105B and the power grid. An HP 6933A D/A converter on the BCD output from the counter had its plus/minus 10 volt output interfaced to the generation plant speed control. The 5321B clock reading was initialised from the local time service (radio time pips) and then used as a reference for fine tuning the 'control system' (the D/A converter to generator speed control coupling) so the up down counter stayed at or near zero reading and power grid time ran in sync with national standard time. I dont know how successful this system was but I think it was in service for several years at a designated system control station. I have the up down counter and the D/A converter almost fully operational again- but only have parts ratted circuit boards from the 5321B clock and I never got the 105B. *** By way of update-- I have some of the original system design docos regarding this scheme, including notes from HP outlining their proposal in response to the original call for tenders etc. Makes interesting reading. And the 5280A up down counter IS now working properly-albeit sometimes erratically, due, I think, to the poor choice of multi pin connectors used between the pcbs and the front panel BCD switch arrays. Cheers DaveB, NZ -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.407 / Virus Database: 268.13.0/465 - Release Date: 6/10/2006 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Good to hear that this project is coming along nicely! (1) Synchronize the 1 PPS output rising edge to be near a 1 PPS input pulse on a one time basis (the 1 PPS edge will have an error of a few instruction cycles which are each 4/Fin long). If this was done the manual setting would be removed. Would this be used to sync a 10 MHz osc to a 1 PPS from a GPS? If yes, then definately. Another idea along these lines: make the clock able to set it's time from a GPS (Oncore would be my choice). (2) Add another mode of operation where the clock runs on it's internal RC oscillator and the timing is determined by an external 1 PPS that needs to always be connected. Not a bad idea, but #3 seems like a better idea: (3) Add a backup Real Time Clock with it's own coin cell battery to allow using the clock in a portable application and allow the clock to be shipped while running. The chip has a 0.1 ppm aging trim capability and there could be a provision to automatically trim it when one of the above precision input frequencies is applied for maybe a day. Then when the input frequency is disconnected the clock would continue to tell the time. There are also many options for alarms. Yes! Yes! Yes! An alarm would be great. Snooze would make it even better! Although, something I could hook a relay up to would be MUCH better than a buzzer. This would then replace my bedside alarm clock. (4) Other displays such as fractional Julian Day number, fractional Modified Julian Day number. sidereal time, or ??? IMHO, features like an alarm, which would make the clock much more acceptable to significant others would make it easier to sell (and buy) than alternate date displays. cheers, glenn ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Yes! Yes! Yes! An alarm would be great. Snooze would make it even better! Although, something I could hook a relay up to would be MUCH better than a buzzer. This would then replace my bedside alarm clock. As long as we are wishing If you have a battery backup on the clock and your 10 MHz source, you would have an alarm clock that didn't get confused when the power went out. You could even power a clock in your bedroom over the coax carrying the 10 MHz signal. -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
On 10/6/06, Hal Murray [EMAIL PROTECTED] wrote: You could even power a clock in your bedroom over the coax carrying the 10 MHz signal. I'd second that. Adding a bias-T to the clock probably wouldn't cost too much. While we are all dreaming, it would be cool to send the power, 10 MHz and 1 PPS all down the same coax. Maxim/Dallas does something like this with their 1-wire line. Has anyone tried something like this with timing signals? Although, it might be easier to just send the 10 MHz via CAT 5, which would also make the wiring cheaper and easier to install (where it's not already installed). cheers, glenn ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
I'd second that. Adding a bias-T to the clock probably wouldn't cost too much. While we are all dreaming, it would be cool to send the power, 10 MHz and 1 PPS all down the same coax. Maxim/Dallas does something like this with their 1-wire line. Has anyone tried something like this with timing signals? The normal way to send both clock and data on the same wire uses a clock at the receiver. For example, you could easily encode a PPS signal as a missing clock pulse. You could also encode it as an inverted pulse or a double height pulse. -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
How about a version that works from the 50/60 Hz power frequency with a 1 PPS output and internal micro clock oscillator? Great for watching the power grid lose time and regain it as the power generated vs. consumed balance varies. If the power line PPS lags behind at an increasing rate, it's time to turn off the air conditioner and run all those clock ovens on battery before the under-frequency relays start cascading. Of course, you need the precision version for comparison. Does anybody in this group look at power line frequency drift? Bill Hawkins ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Does anybody in this group look at power line frequency drift? http://www.leapsecond.com/pages/mains/ /tvb ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
On Fri, Oct 06, 2006 at 03:17:14PM -0500, Bill Hawkins wrote: Does anybody in this group look at power line frequency drift? Not currently, but I did so last year during a few months: http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html Pieter-Tjerk (PA3FWM) ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Hi Bill: On the to do list is a version based on Richard McCorkle's RS232 Time Interval counter. For a minimum cost version a different PIC is needed than the 16F88 used in the Current Version (PC4). Once the TI counter is part of the clock then all kinds of neat things can be done. I'll keep in the looking at the mains. In the PC4 there's a software TI counter good to 1 ms that can be used to trim the Real Time Clock chip. Have Fun, Brooke Clarke w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Bill Hawkins wrote: How about a version that works from the 50/60 Hz power frequency with a 1 PPS output and internal micro clock oscillator? Great for watching the power grid lose time and regain it as the power generated vs. consumed balance varies. If the power line PPS lags behind at an increasing rate, it's time to turn off the air conditioner and run all those clock ovens on battery before the under-frequency relays start cascading. Of course, you need the precision version for comparison. Does anybody in this group look at power line frequency drift? Bill Hawkins ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Does anybody in this group look at power line frequency drift? Somebody once told me that they tried to get frequency info from the Palo Alto utilities. When they finally got through to somebody who knew what was going on, the answer was We aren't tariffed for that. Does anybody have a URL for the frequency specs? (US or California.) I'm also interested in the voltage specs. I poked around on google a while ago but didn't find anything interesting. -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
i believe the us power grid is on 60hz and that the power companies sync up before providing power. that doesnt mean that everyone is in phase. the east is some delayed from the west so that it depends where you are with respect to the prime starting point. long term they are at 60hz to make the clocks on time but for +/- with wwv, anybodys guess at any one point in time. hope that helps some. tom [EMAIL PROTECTED] - Original Message - From: Hal Murray [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, October 06, 2006 4:10 PM Subject: Re: [time-nuts] Features of a Precision Clock? Does anybody in this group look at power line frequency drift? Somebody once told me that they tried to get frequency info from the Palo Alto utilities. When they finally got through to somebody who knew what was going on, the answer was We aren't tariffed for that. Does anybody have a URL for the frequency specs? (US or California.) I'm also interested in the voltage specs. I poked around on google a while ago but didn't find anything interesting. -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Features of a Precision Clock?
Hi: I've got the Precision Clock to work and have some questions about the priority of the features. As it is now the clock allows user selection of the input frequency at power up that determines the instruction clock for the PIC micro controller. The choices are 2.5, 5, 10 or 20 Mhz. The clock displays on line one HH:MM:SS and on line two Day of Week, , Mon, Day of Month. The leap year testing uses the 4, 100 and 400 year rules and so you can determine the day of the week for any Georgian calendar (1583 onwards) date. Setting is by means of 4 buttons, Right, Left, Increment, Decrement. This is very intuitive and quick. During setting the clock continues to keep time. Also a new data field to the right of the seconds appears as 4 hex digits to allow moving the LED/1 PPS output pulse in 1 ms steps. If the input frequency fails then all the fields that can blink do blink and the clock stops. Pressing and holding Right or Left for a few seconds clears the blinking and restarts the clock using the input frequency that was selected at power up. For more see: http://www.pacificsites.com/~brooke/PRC68COM.shtml#PC3 Now for the possible next features to be added. It would be nice to get some feel for how important they are: (1) Synchronize the 1 PPS output rising edge to be near a 1 PPS input pulse on a one time basis (the 1 PPS edge will have an error of a few instruction cycles which are each 4/Fin long). If this was done the manual setting would be removed. (2) Add another mode of operation where the clock runs on it's internal RC oscillator and the timing is determined by an external 1 PPS that needs to always be connected. (3) Add a backup Real Time Clock with it's own coin cell battery to allow using the clock in a portable application and allow the clock to be shipped while running. The chip has a 0.1 ppm aging trim capability and there could be a provision to automatically trim it when one of the above precision input frequencies is applied for maybe a day. Then when the input frequency is disconnected the clock would continue to tell the time. There are also many options for alarms. (4) Other displays such as fractional Julian Day number, fractional Modified Julian Day number. sidereal time, or ??? I don't think there's enough memory for all of the above, probably only one or two of them so I'm hoping to get some input on the priorities. Have Fun, Brooke Clarke -- w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Features of a Precision Clock?
Hi James: Can you point me to an example Bulletin C? Have Fun, Brooke Clarke w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com James Maynard wrote: On receipt of Bulletin C, can you arm this clock to display the upcoming leap second? That's a feature that I would desire. Brooke Clarke wrote: Hi: I've got the Precision Clock to work and have some questions about the priority of the features. As it is now the clock allows user selection of the input frequency at power up that determines the instruction clock for the PIC micro controller. The choices are 2.5, 5, 10 or 20 Mhz. The clock displays on line one HH:MM:SS and on line two Day of Week, , Mon, Day of Month. The leap year testing uses the 4, 100 and 400 year rules and so you can determine the day of the week for any Georgian calendar (1583 onwards) date. Setting is by means of 4 buttons, Right, Left, Increment, Decrement. This is very intuitive and quick. During setting the clock continues to keep time. Also a new data field to the right of the seconds appears as 4 hex digits to allow moving the LED/1 PPS output pulse in 1 ms steps. If the input frequency fails then all the fields that can blink do blink and the clock stops. Pressing and holding Right or Left for a few seconds clears the blinking and restarts the clock using the input frequency that was selected at power up. For more see: http://www.pacificsites.com/~brooke/PRC68COM.shtml#PC3 Now for the possible next features to be added. It would be nice to get some feel for how important they are: (1) Synchronize the 1 PPS output rising edge to be near a 1 PPS input pulse on a one time basis (the 1 PPS edge will have an error of a few instruction cycles which are each 4/Fin long). If this was done the manual setting would be removed. (2) Add another mode of operation where the clock runs on it's internal RC oscillator and the timing is determined by an external 1 PPS that needs to always be connected. (3) Add a backup Real Time Clock with it's own coin cell battery to allow using the clock in a portable application and allow the clock to be shipped while running. The chip has a 0.1 ppm aging trim capability and there could be a provision to automatically trim it when one of the above precision input frequencies is applied for maybe a day. Then when the input frequency is disconnected the clock would continue to tell the time. There are also many options for alarms. (4) Other displays such as fractional Julian Day number, fractional Modified Julian Day number. sidereal time, or ??? I don't think there's enough memory for all of the above, probably only one or two of them so I'm hoping to get some input on the priorities. Have Fun, Brooke Clarke ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
