[time-nuts] NIST "official time"
cquarksnow at gmail.com
Wed Aug 3 17:05:25 UTC 2011
Wondering whether anyone can clarify what discpline the Boulder, CO facility
It appears to be about 20 seconds slower than UTC and I could not find the
relation to other known time scales like TAI, UTC, ET, UT1, GPS or possibly
grid or broadcast-interconnected reference.
On Aug 3, 2011 8:33 AM, "Francis Grosz" <fgrosz at otiengineering.com> wrote:
> Hi, Scott,
> They track because most of Arkansas is part of the Eastern
Interconnection and the transmission systems are tied together through that.
The general shape follows the loading of the system; that is, as the load
increases throughout the day the alternators slip behind; as it decreases
they advance. They try to keep the system frequency accurate to +/- 0.02
Hz. but that integrates out to a worst case of 72 cycles slip or
advance/hour. PNNL has developed the Grid Friendly Grid Monitor software
and you can use that to watch the frequency and accumulated phase error of
the Western Interconnection.
> Here in New Orleans a friend in the power company who was interested
in its history told me a story. In the very early days, frequency control
was pretty poor and it was hard to keep up with the changing load. So by 5
PM every day, every electric clock in the city was 10 or 15 minutes slow.
So overnight they'd speed up the system and so by 8 AM the next morning
every electric clock would be 10 or 15 minutes fast because the total slip
during the day was 20 or 30 minutes. Today we'd consider that absolutely
unacceptable (even for non-Time Nuts), but back then it just was.
> Still, elimination of TEC is idiotic. I had occasion recently to talk
to a couple of very high-level power systems people and they thought it was
crazy as well. Like elimination of leap seconds, we'll just have to see.
> >Message: 7
> >Date: Tue, 02 Aug 2011 21:18:17 -0500
> >From: Scott Newell <newell at cei.net>
> >To: time-nuts at febo.com
> >Subject: [time-nuts] Weird TEC data
> >Message-ID: <848527.81129.qm at smtp109.prem.mail.sp1.yahoo.com>
> >Content-Type: text/plain; charset="us-ascii"; format=flowed
> >Here's the latest plot from my TEC test rigs. Y-axis is phase error
> >(in 60 Hz cycles), X-axis is time in MJD. The plot starts at 7AM local
> >Same serial connected embedded hardware, timestamped on the receipt
> >of first character. One machine (red line) is a Sun running debian,
> >the other (green line) is a Dell PC, also running debian. Both
> >running ntp, of course. One is located in a fairly large city (by
> >Arkansas standards!), the other is out in a small country
> >town. Different utility providers.
> >The general shape and bumps in the plots track nicely, but I'm
> >wondering why there's so many cycles difference after 36 hours.
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