Does anyone know if the NERC experiment (see below) happened or is still underway? -- Richard Langley
>From Wikipedia: "Regulation of power system frequency for timekeeping accuracy was not commonplace until after 1926 and the invention of the electric clock driven by a synchronous motor. Today network operators regulate the daily average frequency so that clocks stay within a few seconds of correct time. In practice the nominal frequency is raised or lowered by a specific percentage to maintain synchronization. Over the course of a day, the average frequency is maintained at the nominal value within a few hundred parts per million.[17] In the synchronous grid of Continental Europe, the deviation between network phase time and UTC (based on International Atomic Time) is calculated at 08:00 each day in a control center inSwitzerland. The target frequency is then adjusted by up to ±0.01 Hz (±0.02%) from 50 Hz as needed, to ensure a long-term frequency average of exactly 50 Hz × 60 sec × 60 min × 24 hours = 4,320,000 cycles per day.[18] In North America, whenever the error exceeds 10 seconds for the east, 3 seconds for Texas, or 2 seconds for the west, a correction of ±0.02 Hz (0.033%) is applied. Time error corrections start and end either on the hour or on the half hour.[19][20] Real-time frequency meters for power generation in the United Kingdom are available online - an official National Grid one, and an unofficial one maintained by Dynamic Demand.[21][22] Real-time frequency data of the synchronous grid of Continental Europe is available at mainsfrequency.com. The Frequency Monitoring Network (FNET) at the University of Tennessee measures the frequency of the interconnections within the North American power grid, as well as in several other parts of the world. These measurements are displayed on the FNET website. Smaller power systems may not maintain frequency with the same degree of accuracy. In 2011, The North American Electric Reliability Corporation (NERC) discussed a proposed experiment that would relax frequency regulation requirements for electrical grids[23] which would reduce the long-term accuracy of clocks and other devices that use the 60 Hz grid frequency as a time base." And spoofing the power grid: http://gpsworld.com/wirelessinfrastructuregoing-against-time-13278/ On Thursday, January 9, 2014,9, at 12:00 PM, Poul-Henning Kamp wrote: > In message <[email protected]>, Hal > Mu > rray writes: > >> The IBM 360 systems starting in 1964 used the power line frequency. (A >> location in low memory got bumped at 300 counts per second. 5 per cycle on >> 60 Hz and 6 per cycle on 50 Hz.) I wonder how much the power timekeeping >> wandered back then relative to today. > > It used to be pretty good, because people used synchronous motors to drive > clocks so the power companies tried to keep the long-term frequency > correct. > > In Denmark they usually lost a couple of seconds during the day and > gained them back during the night, similarly they lost half a minute > over winter and gained it back over summer. > > After deregulation nobody gets paid to keep the long term frequency, > so mains is no good, actually down-right bad, for timekeeping anymore. > > -- > 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. > _______________________________________________ > LEAPSECS mailing list > [email protected] > http://six.pairlist.net/mailman/listinfo/leapsecs ----------------------------------------------------------------------------- | Richard B. Langley E-mail: [email protected] | | Geodetic Research Laboratory Web: http://gge.unb.ca/ | | Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 | | University of New Brunswick Fax: +1 506 453-4943 | | Fredericton, N.B., Canada E3B 5A3 | | Fredericton? Where's that? See: http://www.fredericton.ca/ | ----------------------------------------------------------------------------- _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
