Hi Since the harmonics are locally generated, each site will see different crossings. The same is true of the local load impedance. Bob On Sep 11, 2010, at 5:54 PM, "Stan, W1LE" <stanw1le@verizon.net> wrote: > If the odd harmonics were filtered out, would the zero crossing of the 60 (50) Hz fundamental > be stable enough ? > > Thanks Stan, W1LE Cape Cod FN41sr > > > > > On 9/11/2010 5:08 PM, Bob Camp wrote: >> Hi >> >> You also have load dependent harmonic energy on there that messes up the zero crossings at the micro second level. >> >> Bob >> >> >> >> On Sep 11, 2010, at 3:45 PM, "Poul-Henning Kamp"<phk@phk.freebsd.dk> wrote: >> >>> In message<8459B572-1428-4F6A-8375-AFB4F7225945@cox.net>, "Thomas A. Frank" wr >>> ites: >>> >>>> If so, being within 300 miles of each other suggests that they are >>>> most likely all on the SAME section of the grid, in which case the >>>> phase time of arrival of the electric power waveform should be >>>> constant between them (the zero crossing may not be perfectly >>>> aligned, but it should always be the same differential). >>> Won't work. Utility transformers have load-dependent parasitics >>> which mess this up. It is one of the biggest challenges in >>> doing "autonomous cell based grid control" and similar schemes. >>> >>> -- >>> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >>> phk@FreeBSD.ORG | 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 >>> 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. >

Stan, W1LE wrote: > If the odd harmonics were filtered out, would the zero crossing of the > 60 (50) Hz fundamental > be stable enough ? > > not to 30 ns <grin> Interestingly, one of the markets that Symmetricom/TrueTime/Datum sells into is GPS disciplined receivers used for power control. Power transmission is managed by controlling relative phases in the system, not to mention things like synchronizing generators.

I believe the primary reasons for GPS receivers for the power industry is power line fault location. They use time tagging to measure disturbances to locate a fault and it's accuracy directly determines its resolution. On 9/11/2010 7:33 PM, jimlux wrote: > Stan, W1LE wrote: >> If the odd harmonics were filtered out, would the zero crossing of the >> 60 (50) Hz fundamental >> be stable enough ? >> >> > not to 30 ns <grin> > > > Interestingly, one of the markets that Symmetricom/TrueTime/Datum sells > into is GPS disciplined receivers used for power control. Power > transmission is managed by controlling relative phases in the system, > not to mention things like synchronizing generators. > > > _______________________________________________ > 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. >

Hi Quebec Hydro and I suspect others use it to regulate power generation facilities. Keeps them from simply cross feeding power through the reactance of the distribution network. They have some pretty long lines between source and load.... Bob On Sep 11, 2010, at 10:53 PM, Brian Kirby <kilodelta4foxmike@gmail.com> wrote: > I believe the primary reasons for GPS receivers for the power industry is power line fault location. They use time tagging to measure disturbances to locate a fault and it's accuracy directly determines its resolution. > > On 9/11/2010 7:33 PM, jimlux wrote: >> Stan, W1LE wrote: >>> If the odd harmonics were filtered out, would the zero crossing of the >>> 60 (50) Hz fundamental >>> be stable enough ? >>> >>> >> not to 30 ns <grin> >> >> >> Interestingly, one of the markets that Symmetricom/TrueTime/Datum sells >> into is GPS disciplined receivers used for power control. Power >> transmission is managed by controlling relative phases in the system, >> not to mention things like synchronizing generators. >> >> >> _______________________________________________ >> 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. >