[time-nuts] Weird TEC data
fgrosz at otiengineering.com
Wed Aug 3 15:32:29 UTC 2011
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.
>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 time.
>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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