[time-nuts] Power lines and time
cfharris at erols.com
Mon Aug 22 10:00:46 EDT 2005
Poul-Henning Kamp wrote:
> In message <001301c5a6a2$74803840$0500a8c0 at darius.domain.actdsltmp>, "Bill Hawkins" writes
>>Power companies bill on time-integrated power - watt-hour
>>meters in the US. Watt-hour meters are still mostly driven
>>by electric clocks, in a way. The frequency does matter.
> Uhm, sorry, that is just plain wrong. The Ferrantis (sp?) power
> meter which is the most widely used meter in the world is not
> frequency sensitive within a band of +/- 10% or more.
I have never seen a power meter made by Ferranti in the US. Landis-gyr,
definitely, but not Ferranti. To quote Landis-gyr's website:
" Landis+Gyr Inc. is the world's leading supplier of electricity revenue meters.
Our products include solid-state and electromechanical residential meters,
a full line of solid-state commercial and industrial meters, high-end precision
meters and extensive automated meter reading (AMR) solutions. "
You cannot make a credible claim of "the most widely used meter in the world"
without including the US. We certainly have as many power meters
as all of Europe.
Here most of our meters are of the induction type, which work on the principles of a
split-phase induction motor. They are very easy to recognize by their
horizontal 4 inch corrugated aluminum disk that rotates (hopefully) slowly.
With the induction type power meter, power line frequency is very
important in determining the "hours" part of kilowatt-hours.
A 10% variation in line frequency would cause a 10% variation in power
consumption registered. Induction type power meters will remain accurate
with a 10% variation in power line voltage, however.
Someday, our utilities will convert all of our meters to solidstate units which might
not be so frequency sensitive, but that will be a few hundred billion dollars from now.
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