[time-nuts] Re: Has Line-Frequency Timekeeping Become Less Reliable in the U.S.?

[Hal Murray]

Thomas D. Erb said:
> I recently came across information suggesting that the way the North
> American power grid handles accumulated time error may be changing, and I
> had not realized this was even being discussed.

Old news.  That happened years ago.

I poked around a bit, but I haven't found a good description of when and 
why timekeeping on the US power grid was turned off.  It seems like the 
sort of event that somebody would document with a good story.

Here is a 2017 paper that talks about it being in the works, so less than 
10 years ago.

Time and frequency from electrical power lines
https://www.nist.gov/publications/time-and-frequency-electrical-power-lines

TEC is Time Error Correction.  From the abstract:
The Blackout of 2003 spawned a new regulatory structure for the electric 
power industry to improve reliability, and as an unanticipated side 
effect, a decision process that would most likely eliminate TECs was set 
in motion. The specific proposal is to retire regulatory standards 
designated BAL-004 and WEQ-006. We review the relevant structure and 
governing bodies of the U.S. power grids, and report on the current 
procedural status of these standards. In addition, we review possible 
scenarios for the future of the power system as an elapsed-time reference 
absent TEC. For this, we include analysis of the electric power at USNO, 
as measured over five years. The TECs appear in the data; an analysis with 
the industry-supplied record of the TECs indicates that without them a 
time deviation of about 7 1/2 minutes would have occurred on the Eastern 
Interconnection (grid) between the daylight saving time switches of March 
2016 and November 2016.

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> More specifically, are traditional synchronous clocks now likely to
> accumulate noticeable long-term error?

That depends on what you mean by "noticeable"?

I think it depends on how reliable your power is.  If the power goes out 
for a few minutes every month or two (and has to be reset by hand) then 
you probably won't notice the clock drifting.  If your power is stable for 
a year, you are likely to notice occasionally.


Here are some graphs:
  http://www.glypnod.com/TimeNuts/60Hz/TimeFromPowerLine.html


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