[time-nuts] 60Hz line data

Bill Hawkins bill at iaxs.net
Mon Jul 27 00:37:20 EDT 2015


 
Gotta get some answers from my relative in a PA gas fired plant. A year
ago he told me that the plan to deregulate the number of cycles in a day
had been abandoned. The referenced documents are older than that.

OTOH, there's no other explanation for Hal Murray's observation of the
West Coast grid variation.

Seems to me that all of the rotating synchronous machinery connected to
a grid is constrained by all of that heavy rotating machinery to change
speed quite slowly, like starting to change the direction of a ship
heading to a port about 5 miles out.

There are at least three grids in the US that are independent of each
other in frequency. That reduces the strains on a grid from distant
changes. Power is transferred using high voltage DC transmission lines.
Really large solid state inverters convert between AC and DC. Each
inverter can make any frequency it wants to, subject to the constraints
of all that synchronous machinery.

Frankly, I'm puzzled by the graphs that relate to the time offset. All
that's available to the observer is the line frequency. Relative time
may be inferred with a cycle counter. How is that counter set to UTC?
How can you tell the difference between time error from some reference
point, and cycles gained or lost in the counting equipment - due to
noise and/or computer interrupt servicing routines?

When I asked for data from parts of the country east of the Rockies (on
7/10), I got one reply from a person who is not a member of the list but
reads archive sites. He sent his long term graph for Texas and the link
to a real-time statistics page that gave him the data for the graph.

The statistics are at (strip the stuff after com/ to get the home page
and further details):

http://www.ercot.com/content/cdr/html/real_time_system_conditions.html

His chart (with permission) is at:

http://home.earthlink.net/~schultdw/power/all.png

In this case, the time reference was given by the power company. No
cycles were counted.

Regards,
Bill Hawkins



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