At 10:00 AM 8/22/2005, you wrote:
Poul-Henning Kamp wrote:
In message <[EMAIL PROTECTED]>,
"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.
Try Siemens or ABB then, Ferranti has been taken over if I recall.
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.
You do? Are you sure?
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.
That is certainly the case of older meters and in many states. But is most
definitely not true of newer meters in many jurisdictions. Many regulators
in the US have been very slow on a world basis, to accept newer metering
technology, the New York DPS only registering a wide range of fully solid
state units in 2003.
With the induction type power meter, power line frequency is very
important in determining the "hours" part of kilowatt-hours.
Quite true, hence the reason that many electricity sellers are pushing for
the introduction of solid-state meters much quicker than many regulators
are able to handle.
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.
And herein lies a serious problem for electricity suppliers. With the
problems of inadequate generating capacity and ever increasing demand,
particularly in North America, regulators are directing distributors on
occasions to drop nominal voltages to 100V in controlled brown-outs.
Induction meters then, apparently, tend to read even lower, thus depriving
the distributors of yet more income.
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.
In that case the US will be playing catch up with parts of Canada, Europe,
most of Asia and Oceania where solid state meters, often with remote
reading are the norm rather than the exception - and synchronised mains
frequency has become a fond memory.
John Day
-Chuck Harris
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