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    Time and frequency from electrical power lines
    From: Paul Hirose
    Date: 2018 Aug 14, 15:03 -0700

    Only a few years ago the clock on my microwave oven never needed
    adjustment except for daylight saving time changes and the occasional
    power failure. That's no longer the case. An article at the NIST site
    "Due to the efforts of Henry Warren, inventor of the Telechron electric
    clock, electric power companies have been a source of time and frequency
    reference for the public for over a hundred years. However, advances in
    technology and changes in the electric power industry have generated a
    movement within the industry to end the time-reference service. Power
    systems in the U.S. operate at a nominal 60 Hz, but in actual operation
    they accumulate significant phase error. It must be deliberately backed
    out to keep synchronous clocks on time--a procedure known as Time Error
    Correction (TEC). Today, many electric clocks still depend on the power
    system as the reference oscillator--that is, are synchronous--while
    others use other time references, such as local quartz oscillators and
    networked time servers--a benefit of the Internet of Things. Little is
    known about the overall impact of TEC on timekeeping in modern times.
    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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