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'[EE]: best way to measure KWH'
2000\10\24@010249 by Chris Eddy

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I know this subject has been thrashed somewhere back in history, but I
cannot help it.  My electric company (Duquesne Light in Pittsburgh) is
kicking my ass with the bill.  I am so spitting mad that I could
co-generate.  $300+ per month when not even in the winter is
rediculous.  So I have been pondering making some measurements so that I
can identify where the electrons are all going.  I envision a small PIC
based device with a current transformer that is put on each feeder in
the breaker panel.  A simple serial bus to a PC, and voila, I am logging
use on individual branches.

My question is this.  Do I have to measure phase, via current and
voltage, in order to get a usable value?  And if I do have to have both,
I would prefer to use the CT for current and a galvanic field sense
method to 'see' the voltage.  I would not get an accurate absolute
voltage, but I would get an accurate phase lead/lag.  And if I have the
phase angle and current, how would one then calculate the KVA's?  I once
knew some of this stuff from school, but you know, don't use it and you
loose it.

Chris Eddy~

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2000\10\24@012831 by Michael Shiloh

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> I know this subject has been thrashed somewhere back in history, but I
> cannot help it.  My electric company (Duquesne Light in Pittsburgh) is
> kicking my ass with the bill.  I am so spitting mad that I could
> co-generate.  $300+ per month when not even in the winter is
> rediculous.  So I have been pondering making some measurements so that I
> can identify where the electrons are all going.

Make sure sure you have lightbulbs in all your lamps, and something
plugged in to all your electric outlets, or else the electrons will
leak out.




:-)

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2000\10\24@015645 by Thomas Myers

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HAHAHAHAHAHAHAHAHAHA!!!!!!!!!!

-----Original Message-----
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[spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Michael Shiloh
Sent: Monday, October 23, 2000 9:14 PM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: [EE]: best way to measure KWH


> I know this subject has been thrashed somewhere back in history, but I
> cannot help it.  My electric company (Duquesne Light in Pittsburgh) is
> kicking my ass with the bill.  I am so spitting mad that I could
> co-generate.  $300+ per month when not even in the winter is
> rediculous.  So I have been pondering making some measurements so that I
> can identify where the electrons are all going.

Make sure sure you have lightbulbs in all your lamps, and something
plugged in to all your electric outlets, or else the electrons will
leak out.




:-)

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2000\10\24@024629 by Nigel Goodwin

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In message <39F4E69E.3E6E13C0spamKILLspamnb.net>, Chris Eddy <.....ceddyKILLspamspam.....NB.NET> writes
>I know this subject has been thrashed somewhere back in history, but I
>cannot help it.  My electric company (Duquesne Light in Pittsburgh) is
>kicking my ass with the bill.  I am so spitting mad that I could
>co-generate.  $300+ per month when not even in the winter is
>rediculous.  So I have been pondering making some measurements so that I
>can identify where the electrons are all going.  I envision a small PIC
>based device with a current transformer that is put on each feeder in
>the breaker panel.  A simple serial bus to a PC, and voila, I am logging
>use on individual branches.
>
>My question is this.  Do I have to measure phase, via current and
>voltage, in order to get a usable value?  And if I do have to have both,
>I would prefer to use the CT for current and a galvanic field sense
>method to 'see' the voltage.  I would not get an accurate absolute
>voltage, but I would get an accurate phase lead/lag.  And if I have the
>phase angle and current, how would one then calculate the KVA's?  I once
>knew some of this stuff from school, but you know, don't use it and you
>loose it.

The UK Magazine Everyday and Practical Electronics (EPE) did a project
for this a few years ago using a PIC16C84, the actual sensing was done
using a hall effect transformer device. I built one, it works really
well!.
--

Nigel.

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2000\10\24@042345 by Alan B. Pearce

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As you are trying to find where the power is being used, I suggest you only need to measure current. Within a household the power factor should be close enough to 1 for all appliances that the phase difference between voltage and current will be minimal.

The highest current path is going to be the one drawing the most power unless you are running something like a welding transformer without power factor correction.

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2000\10\24@051052 by R. Monsees

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Could you possibly put this project one the web somewhere ?
I could imagine there a lot of people interested in this topic.

regards,
   Reelf
{Quote hidden}

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2000\10\24@070953 by staff

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Alan B. Pearce wrote:
>
> As you are trying to find where the power is being used, I suggest you only need to measure current. Within a household the power factor should be close enough to 1 for all appliances that the phase difference between voltage and current will be minimal.
>
> The highest current path is going to be the one drawing the most power unless you are running something like a welding transformer without power factor correction.


Yep, I agree. Plus in a household environment the lights only draw
maybe 2% of the total current, "wacky" loads like PCs and electronic
devices maybe 10%, almost always electric heating is the culprit.
Running too many electrons through a wire until it glows hot is a
very crappy way to get heat, I think only 15% to 20% efficient
in most household devices.

Right from the start check the most likely suspects:
* electric stove/toaster etc?
* electric hot water?
* electric heater/air cond?

Things like TV's PC's etc draw a very constant amount of
current and you can just measure them once (or read their
label) and calculate hours used/week. They don't use much.
Just switching the PC monitor off when you walk away
can reduce your PC power waste to a third and doesn't
affect its function.

As a curiosity, I remember something from many years
back when I was an apprentice electrician that fluoro
lights draw huge startup currents, and that if you were
leaving the room for less than 10 minutes it is more
efficient to leave the light on! And don't install
them in bathrooms!
-Roman

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2000\10\24@090536 by Olin Lathrop

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> My question is this.  Do I have to measure phase, via current and
> voltage, in order to get a usable value?  And if I do have to have both,
> I would prefer to use the CT for current and a galvanic field sense
> method to 'see' the voltage.  I would not get an accurate absolute
> voltage, but I would get an accurate phase lead/lag.  And if I have the
> phase angle and current, how would one then calculate the KVA's?  I once
> knew some of this stuff from school, but you know, don't use it and you
> loose it.

In theory, the electric company charges you for the instantaneous voltage
times current integrated over the billing period.  This is also the measure
of the amount of energy delivered.  So, if you wanted to perform the same
measurement, you would have to sample voltage and current "often" compared
to the 60Hz line frequency, then multiply and filter the result to get live
power useage, or accumulate the result to get energy used.

However, if you just want a quick idea of where the power is going, you
probably don't need to be this sophisticated.  Just measuring current will
probably give you a pretty good idea what is going on.  If the current is
low, then the power drain on that line has to be low too.  A high current
could in theory indicate either high power consumption or a large phase
angle.  If both current and voltage are sinusoids, then the power drain is
the RMS current times the RMS voltage times the cosine of the phase angle.
Note that even at a 45 degree phase angle, the power is only 30% less than
indicated by measuring the current alone.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, @spam@olinKILLspamspamcognivis.com, http://www.cognivis.com

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2000\10\24@091946 by Scott Dattalo

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On Tue, 24 Oct 2000, Olin Lathrop wrote:

{Quote hidden}

Olin is right. I used to work for BMI (Basic Measuring Instruments) and we
sampled each phase voltage and current at least 3000 times per
second. Furthermore, we had antialiasing analog filters that were flat in the
analog pass band and had relatively linear phase. Our CT's were about 2%
accurate (worst case) while the PT's were much better than that. We weren't so
interested in metering power per se, but were interested in analyzing it. Often
times the current wave form is far from sinusoidal. So it's necessary to over
sample it.

Scott

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2000\10\24@092549 by Andrew Kunz

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> This is also the measure of the amount of energy delivered.


Not really.  THey charge you as if all phases were delivering the same amount of
power.  If all your energy comes through one phase (because you have thing
plugged into the breaker box in an unbalanced manner) then you will be billed
the same as if ALL phases had that much power coming through them.

In other words, you would be giving away LOTS of money.

Andy

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2000\10\24@093805 by D Lloyd

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part 1 3165 bytes content-type:text/plain; charset=us-ascii
Hi,

Something in my knowledge area-ish......(!)

There are several documents pertaining to the measurement of kWh for the
domestic environment (UK supply).

The metering spec (BS EN61036) gives type tests for the influence of a
range of variables - including harmonics, overcurrent, power factor,
voltage, frequency, etc.

Related is BS EN 50160, 'Voltage characteristics of electricity supplied by
public distribution systems' - which attempts to describe what the
authorities should be supplying.

However, there is no "definative, all encompassing document describing how
the measurement is performed etc. Certainly not one that is free and online
AKAIK, anyway.

Regards,

Dan




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Subject:  Re: [EE]: best way to measure KWH

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> My question is this.  Do I have to measure phase, via current and
> voltage, in order to get a usable value?  And if I do have to have both,
> I would prefer to use the CT for current and a galvanic field sense
> method to 'see' the voltage.  I would not get an accurate absolute
> voltage, but I would get an accurate phase lead/lag.  And if I have the
> phase angle and current, how would one then calculate the KVA's?  I once
> knew some of this stuff from school, but you know, don't use it and you
> loose it.

In theory, the electric company charges you for the instantaneous voltage
times current integrated over the billing period.  This is also the measure
of the amount of energy delivered.  So, if you wanted to perform the same
measurement, you would have to sample voltage and current "often" compared
to the 60Hz line frequency, then multiply and filter the result to get live
power useage, or accumulate the result to get energy used.

However, if you just want a quick idea of where the power is going, you
probably don't need to be this sophisticated.  Just measuring current will
probably give you a pretty good idea what is going on.  If the current is
low, then the power drain on that line has to be low too.  A high current
could in theory indicate either high power consumption or a large phase
angle.  If both current and voltage are sinusoids, then the power drain is
the RMS current times the RMS voltage times the cosine of the phase angle.
Note that even at a 45 degree phase angle, the power is only 30% less than
indicated by measuring the current alone.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, RemoveMEolinspamTakeThisOuTcognivis.com, http://www.cognivis.com

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2000\10\24@100324 by M. Adam Davis

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There is a guy somewhere on the net which has automated his home to a large
degree.  One of the projects he has up is a PIC house meter, which uses
inductive current sensing on his mains.

Ah, here it is:
http://members.tripod.com/~edward_cheung/automa/power.htm

He includes schematics and code (CCS C compiler) for a node on his home
automation network.  His protocol is a master-slave type which he designed
himself, and is described here:
http://members.tripod.com/~edward_cheung/automa/network.htm

It shouldn't be very difficult to cut out the communication routines and replace
them according to your needs.

(for future archival purposes, here is the front door to his site - he indicates
that pages are still being switched around at his site.)
http://members.tripod.com/~edward_cheung/

-Adam

Chris Eddy wrote:
{Quote hidden}

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2000\10\24@105303 by Harold Hallikainen

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       Also have a look at
http://www.analog.com/industry/energymeter/solutions/ic_solutions.html

Harold


FCC Rules Online at http://www.hallikainen.com/FccRules/

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2000\10\24@105306 by M. Adam Davis

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Are you serious?  It sounds like what you are saying is the electric meter finds
the phase with the highest current draw, assumes the other phase is drawing the
same and bases its measurements on that?

I would be very interested in finding out about this.  The larger of my power
hungry appliances use both phases, but the fridge uses only one.  Not to mention
the number of computers that use only one.  The way my place is wired, I
wouldn't be surprised if the loads were not distributed evenly.

This doesn't make sense...  It shouldn't be too difficult to add the current
draw from the phases.

-Adam

Andrew Kunz wrote:
{Quote hidden}

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2000\10\24@111147 by Simon Nield

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-Adam
>This doesn't make sense...  It shouldn't be too difficult to add the current
>draw from the phases.

the electricity company needs balanced loads in order to maximise the efficiency of their lines.

in the UK most houses only get a single phase and which phase you get rotates as you go down one
side of the street, so your neighbours either side will usually be on different phases. this means
the power company is assuming that on average everyone draws the same current. probably a reasonable
assumption most of the time.

in a lot of places in France, and by the sound of it the USA too, you get all three phases and are
supposed to balance the supply yourself - this is probably due to the more rural nature of these
areas; averaging out the phases between houses will work if you only live a few yard from each
other, but if it's half a mile to the next house then the phases will spend most of the time
unbalanced and the lines will need to be derated accordingly... hence the charge for the largest of
the three phases times 3.

I would imagine it would not be hugely expensive to get an electrician to visit your house (whoever
it was that started this thread) and ask them to check the balance of your phases and move circuits
around accordingly... It's just possible that the electricity company may offer this service for a
small charge or for free, or a local energy efficiency department or whatever might offer to help.
then again prehaps not.

I hope that made sense.

Regards,
Simon

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2000\10\24@112015 by Andrew Kunz

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Serious as can be.

If you know what you are doing, you can harness the difference and put it to
work.  My brother set up a textile factory wehre he worked so that the
ventilation fans, a necessary evil, ran off the difference between the phases.
They cooled the building essentially for free.

The sad part was, the plant electrician didn't understand what was going on and
went ballistic.  Only after the accountant told him the electric bill went down
(because the fans had previously been on one phase) did he shut up.

Too mysterious for him, I guess <G>

Andy









"M. Adam Davis" <adavisEraseMEspam.....UBASICS.COM> on 10/24/2000 09:36:28 AM

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Subject: Re: [EE]: best way to measure KWH








Are you serious?  It sounds like what you are saying is the electric meter finds
the phase with the highest current draw, assumes the other phase is drawing the
same and bases its measurements on that?

I would be very interested in finding out about this.  The larger of my power
hungry appliances use both phases, but the fridge uses only one.  Not to mention
the number of computers that use only one.  The way my place is wired, I
wouldn't be surprised if the loads were not distributed evenly.

This doesn't make sense...  It shouldn't be too difficult to add the current
draw from the phases.

-Adam

Andrew Kunz wrote:
>
> > This is also the measure of the amount of energy delivered.
>
> Not really.  THey charge you as if all phases were delivering the same amount
of
{Quote hidden}

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2000\10\24@112223 by Alan B. Pearce

face picon face
>in the UK most houses only get a single phase and which phase
>you get rotates as you go down one

Another way it is done (I know New Zealand has this as common practice) is if you have an electric stove then 2 phases will be brought into the house, and the wiring on the stove is designed so the elements can be split to separate phases. This reduces the size of wire needed to the stove as well as evening up the phase loading, but in this arrangement separate meters are used on each phase. Typically the oven element would be on one phase, and the cooktop elements on a separate phase. It is treated as 2 separate single phase installations.

Another hang-up is that a lot of electric water heating and house heating is also used. This will almost automatically result in a 2 phase installation. If gas water and house heating is used, then the stove may have both feeds commoned up and only a single phase into the house.

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2000\10\24@124119 by Michael Rigby-Jones

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{Quote hidden}

I have always had the understanding that electricity to heat was one of the
most efficient energy conversions you could get.  Incandescent lamps OTOH
must be about the bottom of the ladder in terms of efficiency.

Mike

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2000\10\24@133135 by Dan Michaels

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Michael Shiloh wrote:
>> I know this subject has been thrashed somewhere back in history, but I
>> cannot help it.  My electric company (Duquesne Light in Pittsburgh) is
>> kicking my ass with the bill.  I am so spitting mad that I could
>> co-generate.  $300+ per month when not even in the winter is
>> rediculous.  So I have been pondering making some measurements so that I
>> can identify where the electrons are all going.
>


Guess it is time to start looking at home energy conservation.
New millenium economics. Clearly the wave of the future. Maybe
X-10 for home control, etc. There are a bunch of links to "Smart
Homes" on my Emerging Technologies page:

http://www.users.qwest.net/~oricom/emerge2.htm

Also, article in the paper was talking about natl energy prices
possibly doubling this winter. Energy "deregulation" in california
among other places resulting in soaring prices. [let's hear it for
free-market libertarianism - BruceC is right].

Among others, a company called Coactive Networks has been developing
web-accessible home energy gateways:

http://www.coactive.com/

best regards,
- Dan Michaels
Oricom Technologies
===================

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2000\10\24@134329 by Nigel Goodwin
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In message <EraseME39F5B83A.EE2D383spamspamspamBeGoneewetel.net>, R. Monsees <bam-
RemoveMEmonKILLspamspamEWETEL.NET> writes
>Could you possibly put this project one the web somewhere ?
>I could imagine there a lot of people interested in this topic.

The copyright belongs to EPE, so I couldn't scan it and post it on the
web, you could try asking the magazine - they are on the web at
http://www.epemag.wimborne.co.uk - you can download the software from
there!.
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2000\10\24@135752 by M. Adam Davis

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Looks like its time to check how my circuits are layed out.  Yeesh.

So the ideal situation would drawing current off both lines at the same rate.
If, for instance, you had two refridgerators you would want to set them up with
an intelligent controlling system so that they would both be running at the same
time when one needed cooling (as much as practical...).

Of you could develop a converter (If you could make one efficient enough) which
would take power equally from both phases regardless of the load you placed on
either phase of its output.  Or I could just start buying equipment from the UK,
setting all my PS's to 240, etc.  It's too bad they don't use the One True Power
Line Frequency (TM) over there.  ;-)

I suppose one could wrap two coils around the incoming mains lines, and hook
them up in a configuration (similar to Ground Fault Protection circuits) such
that a voltage will develop across two of the wires if the current draw on the
two aren't even (and thus cancelling each other out).  You could measure that
voltage and extrapolate the difference in current between the two as a simple
"how much are we being charged for that we aren't using" indicator.  One could
use a bi-color LED with voltage/current limiting to show which phase is drawing
more current, with brightness showing how bad the situation is.

Lots of fun here.  If it's bad at my place, it would be bad in the places around
me.  I could set up a little business!  (Save $50 a year on your electric bill!
I'll rearrange your circuit breakers for only $80!  ;-)  Of course I'm an
electrician.  What?  Oh, well no, I'm not licensed, but *click*)

-Adam

Andrew Kunz wrote:
{Quote hidden}

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2000\10\24@141710 by Dwayne Reid

flavicon
face
At 09:24 AM 10/24/00 -0400, Andrew Kunz wrote:
> > This is also the measure of the amount of energy delivered.
>
>
>Not really.  THey charge you as if all phases were delivering the same
>amount of
>power.  If all your energy comes through one phase (because you have thing
>plugged into the breaker box in an unbalanced manner) then you will be billed
>the same as if ALL phases had that much power coming through them.
>
>In other words, you would be giving away LOTS of money.

I do NOT believe this to be the case.  One of our products currently in
beta test is a device used by power companies to verify the accuracy of
their meters installed in industrial plants.  I haven't had much to do with
the project but I know that I would have sat up and taken notice if we had
to emulate that behavior.  As far as I know, we simply add the sum of the
powers measured in each of the phases to come up with the total.

dwayne



Dwayne Reid   <@spam@dwayner@spam@spamspam_OUTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 16 years of Engineering Innovation (1984 - 2000)

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2000\10\24@142457 by Homale Sux

picon face
Try the Circuit Cellar or may be it was nuts and volts that had a PIC kWH
project.


In message <spamBeGone39F5B83A.EE2D383spamKILLspamewetel.net>, R. Monsees <bam-
.....monspam_OUTspamEWETEL.NET> writes
>Could you possibly put this project one the web somewhere ?
>I could imagine there a lot of people interested in this topic.

The copyright belongs to EPE, so I couldn't scan it and post it on the
web, you could try asking the magazine - they are on the web at
http://www.epemag.wimborne.co.uk - you can download the software from
there!.
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2000\10\24@142710 by Andrew Kunz

flavicon
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Dwayne,

According to the local utility (GPU), this is the method they use for
residential and commercial customers.

According to our customers (big comm companies) this is how they are billed.  A
good portion of our engineering goes into assuring balanced used of the phases.

Andy








Dwayne Reid <TakeThisOuTdwayner.....spamTakeThisOuTPLANET.EON.NET> on 10/24/2000 02:14:06 PM

Please respond to pic microcontroller discussion list <TakeThisOuTPICLISTKILLspamspamspamMITVMA.MIT.EDU>








To:      .....PICLISTspamRemoveMEMITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [EE]: best way to measure KWH








At 09:24 AM 10/24/00 -0400, Andrew Kunz wrote:
{Quote hidden}

I do NOT believe this to be the case.  One of our products currently in
beta test is a device used by power companies to verify the accuracy of
their meters installed in industrial plants.  I haven't had much to do with
the project but I know that I would have sat up and taken notice if we had
to emulate that behavior.  As far as I know, we simply add the sum of the
powers measured in each of the phases to come up with the total.

dwayne



Dwayne Reid   <RemoveMEdwaynerspamspamBeGoneplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 16 years of Engineering Innovation (1984 - 2000)

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2000\10\24@151841 by Ken Godee

flavicon
face
This topic seemed interesting so I emailed one of the local
electric companies and the following is a response from one of their
engineers.
-------------------------- snip ------------------------------------------------------
"The electric meter actually simultaneously measures voltage and
current on each leg, and then adds them up.  This is obviously a
pretty simplified version of what's happening inside the meter, but
that's the bottom line for your electric bill.  If your load is
unbalanced between the two legs, you're not getting charged
double for the unbalanced portion.
It's actually a vector multiplier, where the voltage vector is multiplied
by the current vector, and the product of those two is what pushes
the wheel around.  But I'm sure that's much more than any normal
person (I, on the other hand, am an engineer) would want to know.
The only real problem with leg unbalance is that SRP transformers
can get warmer if the phases are unbalanced, but that's really
SRP's problem, and not yours to worry about."
------------------------ snip ---------------------------------------------------------



The Perfect Image Graphics Co.
2429 W. 12th St.
Tempe, AZ 85281

800-533-8732

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2000\10\24@152523 by Steve Smith

picon face
Maybe the best way to balance the load across three phases is to rectify it
and then invert bacK to ac single phase at the sum of the power consumed from
the phases. Hence the burden of the rectifier would be balanced across the
supply ensuring that paymet for unused electrons was minimised (a UPS)  is
then called for ? Side effect is that if a battery is added the power is
maintained during breif problems with supply quality.
Just a thaught maybe a little silly but a it offers a soulition to waste !

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2000\10\24@155416 by Andy Howard

picon face
> From: "Michael Rigby-Jones" <spamBeGonemrjones@spam@spamspam_OUTNORTELNETWORKS.COM>
> > From: Roman Black [SMTP:TakeThisOuTfastvidspamspamEZY.NET.AU]

> > Yep, I agree. Plus in a household environment the lights only draw
> > maybe 2% of the total current, "wacky" loads like PCs and electronic
> > devices maybe 10%, almost always electric heating is the culprit.
> > Running too many electrons through a wire until it glows hot is a
> > very crappy way to get heat, I think only 15% to 20% efficient
> > in most household devices.
> >
> I have always had the understanding that electricity to heat was one of
the
> most efficient energy conversions you could get.  Incandescent lamps OTOH
> must be about the bottom of the ladder in terms of efficiency.

I think you're only looking at one part of the conversion process though.
Take the case of e.g. a gas-fired home heating system compared to electric
heating from generated from a gas-fired power station (chosen to keep the
comparison fair).

In the latter case you burn the gas to produce heat, convert the resulting
energy to electricity with a pretty low conversion efficiency, transmit the
electricity with the attendant losses in several transformers and many miles
of cable and then use it to heat the house. In the former case you just burn
the gas to produce heat.





.

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2000\10\24@160106 by Bob Ammerman

picon face
I think the answer to this varies according to the type and size of service.

Demand charges are typically  based on the highest phase, but usage chargers
are usually summed across phases.

I've developed hydro plant control systems (like at Niagara Falls, 2.5GW of
generation!) and metering there is certainly done phase-by-phase for usage.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2000\10\24@160110 by Bob Ammerman

picon face
----- Original Message -----
From: Simon Nield <simon.nieldEraseMEspamQUANTEL.COM>
To: <RemoveMEPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU>
Sent: Tuesday, October 24, 2000 11:07 AM
Subject: Re: [EE]: best way to measure KWH


> -Adam
> >This doesn't make sense...  It shouldn't be too difficult to add the
current
> >draw from the phases.
>
> the electricity company needs balanced loads in order to maximise the
efficiency of their lines.
>
> in the UK most houses only get a single phase and which phase you get
rotates as you go down one
> side of the street, so your neighbours either side will usually be on
different phases. this means
> the power company is assuming that on average everyone draws the same
current. probably a reasonable
> assumption most of the time.
>
> in a lot of places in France, and by the sound of it the USA too, you get
all three phases and are
> supposed to balance the supply yourself - this is probably due to the more
rural nature of these
> areas; averaging out the phases between houses will work if you only live
a few yard from each
> other, but if it's half a mile to the next house then the phases will
spend most of the time
> unbalanced and the lines will need to be derated accordingly... hence the
charge for the largest of
> the three phases times 3.

Almost all residential power in the US is single phase 220V with a central
neutral. ie: you get 110V from neutral to each leg (which are 180 degrees
apart) and 220V betweent the two hots. Stoves, dryers and other large loads
are 220V, normal lighting and utility outlets are 110V on one leg.

Commercial power is often 3-phase. A common configuration is 208-Y (ie: 208V
from leg to leg, with a central neutral). The leg to neutral voltage is
(surprise) 110V. A lot of commercial lighting is 208V single phase, driven
by two legs of the service.

You also find 240V delta and 480V delta, often for large motors.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

>
> I would imagine it would not be hugely expensive to get an electrician to
visit your house (whoever
> it was that started this thread) and ask them to check the balance of your
phases and move circuits
> around accordingly... It's just possible that the electricity company may
offer this service for a
> small charge or for free, or a local energy efficiency department or
whatever might offer to help.
> then again prehaps not.
>
> I hope that made sense.
>
> Regards,
> Simon
>
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>
>

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2000\10\24@160115 by Bob Ammerman

picon face
Direct resistive conversion of electricity to heat is highly efficient in
one sense.

However, a given amount of electricity, used to drive a heat-pump (ie:
air-conditioner) can move much more heat than it can create resisitively.
(common units have EER (energy efficiency ratings) of 12+).

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)


----- Original Message -----
From: Michael Rigby-Jones <@spam@mrjonesRemoveMEspamEraseMENORTELNETWORKS.COM>
To: <EraseMEPICLISTspam@spam@MITVMA.MIT.EDU>
Sent: Tuesday, October 24, 2000 12:37 PM
Subject: Re: [EE]: best way to measure KWH


> > {Original Message removed}

2000\10\24@160126 by Bob Ammerman

picon face
As mentioned before:

Usage metering: sum of phases

Demand metering: max of phases

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\10\24@160721 by hard Prosser

flavicon
face
What about heat pumps then, where the heat "output" exceeds the energy
input?  - A heat pump driven from (mainly) hydro power must be close to
optimum overall "efficiency".


Richard P








I think you're only looking at one part of the conversion process though.
Take the case of e.g. a gas-fired home heating system compared to electric
heating from generated from a gas-fired power station (chosen to keep the
comparison fair).

In the latter case you burn the gas to produce heat, convert the resulting
energy to electricity with a pretty low conversion efficiency, transmit the
electricity with the attendant losses in several transformers and many
miles
of cable and then use it to heat the house. In the former case you just
burn
the gas to produce heat.





.

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2000\10\24@160931 by Elton Spode

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unsubscribe

----- Original Message -----
From: Ken Godee <@spam@kenspam_OUTspam.....PERFECT-IMAGE.COM>
To: <spamBeGonePICLISTEraseMEspamMITVMA.MIT.EDU>
Sent: Tuesday, October 24, 2000 5:15 PM
Subject: Re: [EE]: best way to measure KWH


> This topic seemed interesting so I emailed one of the local
> electric companies and the following is a response from one of their
> engineers.
> --------------------------
snip ------------------------------------------------------
{Quote hidden}

snip ---------------------------------------------------------
{Quote hidden}

"[BUY]:","[AD]:" =Ads
>
>
>
>

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2000\10\24@161139 by Bob Ammerman

picon face
Wow,

You eMailed the local electric company and got this detailed an answer?

I expected something like:

"The wheel goes around faster when you turn on more lights". :-)

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\10\24@181405 by Olin Lathrop

flavicon
face
> > Running too many electrons through a wire until it glows hot is a
> > very crappy way to get heat, I think only 15% to 20% efficient
> > in most household devices.
> >
> I have always had the understanding that electricity to heat was one of
the
> most efficient energy conversions you could get.  Incandescent lamps OTOH
> must be about the bottom of the ladder in terms of efficiency.

Yup, incandescent lamps are over 85% efficient as heaters, and less than 15%
efficient as lights.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olinspamBeGonespamcognivis.com, http://www.cognivis.com

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2000\10\24@181417 by Olin Lathrop

flavicon
face
> What about heat pumps then, where the heat "output" exceeds the energy
> input?  - A heat pump driven from (mainly) hydro power must be close to
> optimum overall "efficiency".

Yes, depending on the outside temperature (assuming the desired inside
temperature is usually about the same, about 70F or 21C), a heat pump can be
a more efficient way to heat a house than a resistor.  That's because when
the temperature differences are low, it is easier to move heat energy around
than to convert it from incoming energy.  For example, it may only take 50W
of electric power to bring in 100W of heat from outside whereas it takes
100W of electric power to produce 100W of heat inside.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, RemoveMEolin@spam@spamspamBeGonecognivis.com, http://www.cognivis.com

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2000\10\24@183407 by Dwayne Reid

flavicon
face
At 03:24 PM 10/24/00 -0400, Steve Smith wrote:
>Maybe the best way to balance the load across three phases is to rectify it
>and then invert bacK to ac single phase at the sum of the power consumed from
>the phases. Hence the burden of the rectifier would be balanced across the
>supply ensuring that paymet for unused electrons was minimised (a UPS)  is
>then called for ? Side effect is that if a battery is added the power is
>maintained during breif problems with supply quality.
>Just a thaught maybe a little silly but a it offers a soulition to waste !

That can get REAL complicated when you consider that you have to keep the
harmonic currents down.  About the only way to do that is use a power
factor correction type switch mode input stage, then feed the
inverter.  Horrible things start to happen when you consume a lot of energy
through rectifiers / filter caps.

dwayne



Dwayne Reid   <.....dwayner@spam@spamEraseMEplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 16 years of Engineering Innovation (1984 - 2000)

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2000\10\24@184908 by M. Adam Davis

flavicon
face
I remember a discussion on power meters a long time ago on
sci.electronics.something-or-other, though that one focused on whether they
measured real power, apparent power, etc.

The conclusion was that different power companies did it differently, that there
was a lot of latitude in federal regulations (in the US) on how power is
measured and billed.

At any rate, I will probably try and balance my loads anyway.  One less
opportunity for the transformer outside my door to explode.

Actually, winter is coming on.  Maybe we should all unbalance our loads so the
transformers get warm and provide heat for the homeless...  (Another Brilliant
Idea by Adam (TM) ;-)

-Adam

Ken Godee wrote:
{Quote hidden}

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2000\10\24@191218 by M. Adam Davis

flavicon
face
Actually, in the former case you just have lots of gas substations which
maintain resevoirs of gas, maintain pressure, and pump gas to and from various
other places, all these systems use electricity.

Not that I'm saying it is less efficient, just that you are also looking at only
part of the process as well.

-Adam

Andy Howard wrote:
{Quote hidden}

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2000\10\24@214725 by Reginald Neale

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>

Chris:

Check out http://www.sames.co.za/energy/sa9607m.html

They make a line of ICs for energy consumption measurement.

Reg Neale

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2000\10\24@220341 by Chris Eddy

flavicon
face
Well, after listening to the great ideas and comments, it appears that in order to
meet my initial goal, I need to do the following:

Place a CT type device on each leg in the box to measure current with a PIC at each
location;
Have one master box that monitors the voltage on the line with a second line
transformer;
Send the voltage sinusoid down one of the pins to all of the current monitor devices
so that every one gets the v data
(it is the same for all, after all). Sorry, two voltage waveforms, two legs.
Let each node calculate real power or energy as may be the case
poll the devices for their consumption data, and phase angle, et cetera back to the
main unit
Release the totalized data through a serial port to a WINTEL PC for display.

Now all I need is time to do it all.  Anyone have any great ideas for that?

Chris Eddy~

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2000\10\25@020919 by Nigel Goodwin

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In message <.....85256982.00653C2F.00RemoveMEspamtdipower.com>, Andrew Kunz
<.....akunzSTOPspamspam@spam@TDIPOWER.COM> writes
>Dwayne,
>
>According to the local utility (GPU), this is the method they use for
>residential and commercial customers.
>
>According to our customers (big comm companies) this is how they are billed.  A
>good portion of our engineering goes into assuring balanced used of the phases.

When I was at technical college, just opposite was a large sweet
factory, we were always told by the lecturers that they employed a man
solely to switch capacitors (huge ones!) to keep the phase of their
consumption correct - failing to do so caused much larger bills as it
caused the meters to read high.
--

Nigel.

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2000\10\25@021547 by Nigel Goodwin

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In message <012701c03df4$d2c033e0$RemoveME5fc91440spamspamBeGonesciencekit.com>, Bob Ammerman
<spamBeGoneRAMMERMANKILLspamspam@spam@PRODIGY.NET> writes
>Almost all residential power in the US is single phase 220V with a central
>neutral. ie: you get 110V from neutral to each leg (which are 180 degrees
>apart) and 220V betweent the two hots. Stoves, dryers and other large loads
>are 220V, normal lighting and utility outlets are 110V on one leg.

Isn't that two phase, not single phase?.

>Commercial power is often 3-phase. A common configuration is 208-Y (ie: 208V
>from leg to leg, with a central neutral). The leg to neutral voltage is
>(surprise) 110V. A lot of commercial lighting is 208V single phase, driven
>by two legs of the service.

As had been previously mentioned here, the UK usually just feeds houses
with single phase 230 volt, with alternate houses being feed from
alternate phases (to balance the load and reduce the size of the neutral
conductor). In the workshop where I work three phase was installed when
it was built, but only one phase is actually used, the other two don't
even feed a meter, but are there for possible future expansion.

Incidentally, the length of mains leads on portable appliances (irons
etc.) is limited by UK legislation, as is the spacing of mains sockets
on different phases, so you can't reach from one appliance to another
and receive a 440 volt shock!.
--

Nigel.

       /--------------------------------------------------------------\
       | Nigel Goodwin   | Internet : nigelgspam_OUTspam@spam@lpilsley.co.uk           |
       | Lower Pilsley   | Web Page : http://www.lpilsley.co.uk       |
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2000\10\25@033938 by staff

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Michael Rigby-Jones wrote:
{Quote hidden}

Wow! In future I will be real careful how I phrase things! :o)
Between you and Olin you are both perfectly correct. But I was not
talking physics, I was talking about heating THINGS.

Electric bar heaters, the most common, are very inefficient for
heating the house. The heat energy may be very efficient at heating
the coil of wire in the element, but useful heat radiated to
a few feet away might be quite low. An electric bar heater with a fan
to distribute the hot air is much better. A micro furnace heater
which heats a small wire very very hot and then blows the super hot
air around the room is even better.

A stove element may be very eficient internally, but wastes a lot of
heat energy radiated downward away from your frypan, more energy
wasted heating the stovetop mass a few degrees, etc etc. An inductive
stove top generates the heat in the frypan itself, and has a heat
insulating stovetop so that the heat is kept in the frypan.
Much more efficient, although this might not be as obvious when
thinking about the theoretical models of the two designs.

So if we are going to talk efficiency of household goods it might
be smart to look at the power used vs actually what it achieves,
rather than argue the perfect theoretical model.

Since both yours and Olins arguments are perfectly correct I have
to assume the fault was mine for not making it more clear exactly
what the heck I was talking about! ;o)
-Roman

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2000\10\25@035431 by staff

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M. Adam Davis wrote:
{Quote hidden}

Reminds me of a conversation with an old timer electrician when
I was a young apprentice. He told me in the "old days" they used to
stick a big magnet off a loudspeaker next to the power meter,
and it slowed down the rate of turn and hence it's measured
power. He may have been pulling my leg but I suppose there
are a couple of reasons it would work. I AM NOT advising anyone
try this of course.
-Roman

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2000\10\25@040428 by Michael Rigby-Jones

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{Quote hidden}

       From:   Roman Black [SMTP:fastvidspam@spam@EZY.NET.AU]
       Sent:   Wednesday, October 25, 2000 9:37 AM
       To:     EraseMEPICLISTRemoveMEspamSTOPspamMITVMA.MIT.EDU
       Subject:        Re: [EE]: best way to measure KWH

{Quote hidden}

OK, I see what you mean now, I guess I read your post too literaly :o)  I
definately agree that electric heating, especialy radiant types are very
inefficient from the point of view of usefully using the heat produced.  I
also think that central heating, where gas is burned to heat water which is
pumped around to various radiators to heat the air is also a very poor
method of keeping a house warm.

Cheers

Mike

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2000\10\25@090540 by Olin Lathrop

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> Place a CT type device on each leg in the box to measure current with a
PIC at each
> location;
> Have one master box that monitors the voltage on the line with a second
line
> transformer;
> Send the voltage sinusoid down one of the pins to all of the current
monitor devices
> so that every one gets the v data
> (it is the same for all, after all). Sorry, two voltage waveforms, two
legs.
> Let each node calculate real power or energy as may be the case
> poll the devices for their consumption data, and phase angle, et cetera
back to the
> main unit
> Release the totalized data through a serial port to a WINTEL PC for
display.
>
> Now all I need is time to do it all.  Anyone have any great ideas for
that?

Sounds like the individual PICs need two channels of A/D and some serial I/O
to communicate the result.  IIC sounds good because you can connect all the
measuring PICs on the same bus and have them interrogated by the master at
regular intervals.  The master then packages up the data and sends it to a
PC via RS-232.  It sounds like the fancy display software on the Windows
side will be more complicated to write than the PIC code.

So, you need a PIC with two channels of A/D (8 bits is fine) and IIC.  It
looks like the smallest non-vaporware part is 28 pins, of which there are
several to choose from.  I would go for one of the flash parts, like the
16F872.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, RemoveMEolinKILLspamspamTakeThisOuTcognivis.com, http://www.cognivis.com

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2000\10\25@090544 by Olin Lathrop

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> When I was at technical college, just opposite was a large sweet
> factory, we were always told by the lecturers that they employed a man
> solely to switch capacitors (huge ones!)

Sounds like a job for a PIC <g> (must have been a union shop).

> to keep the phase of their
> consumption correct - failing to do so caused much larger bills as it
> caused the meters to read high.

Power companies often measure phase angle of large customers, and charge
more as the phase angle goes up.  A large phase angle will not make the
power meters read more because more power is not being delivered.  It will
however, cause more current in the transmission lines to deliver the same
power, which costs the electric company more, which they charge for.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, spamBeGoneolinspam@spam@cognivis.com, http://www.cognivis.com

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2000\10\25@090547 by Olin Lathrop

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> >Almost all residential power in the US is single phase 220V with a
central
> >neutral. ie: you get 110V from neutral to each leg (which are 180 degrees
> >apart) and 220V betweent the two hots. Stoves, dryers and other large
loads
> >are 220V, normal lighting and utility outlets are 110V on one leg.
>
> Isn't that two phase, not single phase?.

No.  My house is a good example.  All three power phases get delivered to
our neighborhood.  There is a transformer on the last power pole to my house
which has a single primary winding that is driven from one of the three
phases.  The secondary is center tapped, with the center grounded to a big
copper bar sunk into the ground by the circuit breaker box in my basement.
Each half of the secondary is 110V, which makes 220V accross the ends of the
secondary.  The about half the 110V circuits are wired between one end of
the secondary and ground, and the other half to the other end of the
secondary.  The 220V drier circuit is wired from one end of the secondary to
the other.

Yes, I have two 110V "phases" in my house that are 180 degrees apart.  But
from the power company point of view my house is fed completely from one of
their three phases.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, RemoveMEolinspam_OUTspamcognivis.com, http://www.cognivis.com

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2000\10\25@095849 by Andrew Kunz

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Bit-banged comms (I2C or other) should work fine (especially if you are doing
both sides), so you can get away with a PIC12C671.

Andy

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2000\10\25@111137 by Mark Peterson

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part 1 1981 bytes content-type:text/plain; charset=us-ascii

For the standard split phase 240/120 service, you only need a single
voltage and current input to calculate total delivered power.

I am pathetic at ASCI art but I thought I'd better throw the following
sketch together rather than attaching a graphics file.



                     Imeter
                      |  |
                      |  |  Current Transformer
 Leg1                 UUUU
<--------------+-------------------------
<              |      ------
<           Vmeter    |    |
<              |      |    |
< Neutral      |      |    |
<----------------------------------------
<              |      |    |
<              |      |    |
<              |      -------------------
< Leg2         |           |
<--------------+------------

This is the standard metering arrangement used by utilities.  The real
power value is the product of the instantaneous voltage and current.
Although it may not be clear in my drawing, the single potential value used
is the phase-to-phase nominal 240 VAC value.  The current value used is the
output from a current transformer.  The two outside phase legs are run
through the CT in opposition to eachother.

The power calculation for this arrangement is: P=V*C/2.

Assume a balanced load, or essentially a single 240 phase-to-phase load.
Leg1 and leg2 currents are equal and in phase.  For simplicity's sake,
assume the CT ratio is 1:1 and that the current draw for this load is 10
amps.  V will equal 240 volts.  I, the output of the CT, will equal 2*10 or
20 amps.  Thus P=240*20/2=2400 watts.

Assume a single phase-to-neutral load of 10 amps on leg1 with no load on
leg2.  V will equal 240 volts.  I will equal 10 amps.  P=240*10/2=1200
watts.

Assume the first leg single phase-to-neutral load of 12 amps, the second
leg single phase-to-neutral load of 8 amps, and a phase-to-phase load of 10
amps.  Remember, the current in leg2 due to the second leg single
phase-to-neutral load is 180

part 2 715 bytes content-type:text/plain; charset=iso-8859-1
(decoded quoted-printable)


out of phase with the current in leg1. V=240.
I=12+8+2*10=40.  P=240*40/2=4800 watts.

Check it.  Leg 1: P=120*12=1440.  Leg2: P=120*8=960.  P-to-P load:
P=240*10=2400.  Total P=1440+960+2400=4800 watts.


By the way, no electric utility, in the US anyway, bases its charges on a
residential customers imbalance.  For some large industrial customers,
there may be a negotiated agreement for penalty charges for extreme
imbalance or poor power factors.  Of course, for many reasons it is
desireable to have loads as balanced as possible, but you'd be nuts to hire
someone to balance your household loads with the idea in mind that your
bill will go down.


Mark P.


part 3 146 bytes
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2000\10\25@122255 by rottosen

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For an inexpensive plug-in type of wattmeter see:
http://www.doubleed.com/  It has a PIC in it :-)

Are you going to use some kind of clip on current transformer, a torrid
with the wire through it or wire the transformer into the current path?

If you intend to wire in the transformer then you should check into a
Magnatek product. It is number CSE-187L available from Digi-Key (catalog
# 237-1103-ND) for $2.89 each (US$). They are PCB mount which could be
good or bad in your case.


Chris Eddy wrote:
{Quote hidden}

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2000\10\25@150325 by dre Domingos F. Souza

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>Wow,
>You eMailed the local electric company and got this detailed an answer?
>I expected something like:
>"The wheel goes around faster when you turn on more lights". :-)

       If it were here in Brazil, they would say "I don't know. Don't know who knows."


--------------8<-------Corte aqui-------8<--------------

       All the best!!!
       Alexandre Souza
       xandinhospamspaminterlink.com.br

--------------8<-------Corte aqui-------8<--------------

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2000\10\25@171047 by Peter L. Peres

picon face
Is there not some way to use a magamp to multiply the voltage and current
components in place and obtain a single AC output whose magnitude reflects
direct power ? I think that there is, and I think that it requires one
single core with 4 windings, one being the current winding, one the
voltage winding, and one the output winding (the fourth winding cancels
the AC in the output when there is no current). A magamp is a multiplier
of sorts. Given the right magnetic materials you can probably make one
@home. I'm tempted to experiment using some ferrite cores that I have full
data for. The saturation would be provided by the voltage coil (of
course).

On a sideline, what is the minimum power registered by a certain size of
counter ? These are mechanical devices and if one would have say a 30 kW
panel and draw 30W continuously it would be 0.1%. Maybe the friction will
be enough to stop the wheel...

Peter

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2000\10\25@191259 by Nigel Goodwin

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In message <002f01c03e82$3fb43860$260bf6cd@pc>, Olin Lathrop
<spam_OUTolin_piclistspam_OUTspamspam_OUTCOGNIVIS.COM> writes
>> When I was at technical college, just opposite was a large sweet
>> factory, we were always told by the lecturers that they employed a man
>> solely to switch capacitors (huge ones!)
>
>Sounds like a job for a PIC <g> (must have been a union shop).

It was a long!!!!! time before PIC's, in fact before microprocessors,
around the same time we used the first calculators at college, they were
huge desk mounted TTL based machines :-). We also once (and only once!)
were shown their teletype link to a university computer, running a 3D
tic-tac-toe game written in BASIC - they had their own computer, but it
was a valve (tube - for our USA readers) version, and I don't believe it
ever actually worked :-).

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       /--------------------------------------------------------------\
       | Nigel Goodwin   | Internet : nigelgspam_OUTspamlpilsley.co.uk           |
       | Lower Pilsley   | Web Page : http://www.lpilsley.co.uk       |
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2000\10\25@191302 by Nigel Goodwin

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In message <003501c03e84$4c4e50e0$260bf6cd@pc>, Olin Lathrop
<RemoveMEolin_piclistKILLspamspam@spam@COGNIVIS.COM> writes
{Quote hidden}

Interesting point, you get two phase, but from a single phase feed -
thinking about it, I don't see how you could get two phase from a three
phase feed otherwise - so it makes sense. We don't have these problems
in the UK, we get 230 volts single phase everywhere!.
--

Nigel.

       /--------------------------------------------------------------\
       | Nigel Goodwin   | Internet : nigelgspamBeGonespam.....lpilsley.co.uk           |
       | Lower Pilsley   | Web Page : http://www.lpilsley.co.uk       |
       | Chesterfield    | Official site for Shin Ki and New Spirit   |
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2000\10\25@221524 by Bob Ammerman

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I guess it's a cultural thing.

In the US we _never_ think of our 220V center tapped ground (ie: two legs
180 degrees apart) power as two phase. It is just single phase over here.

Three phase is wired either delta or wye and has three phases 120 degrees
apart.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\10\26@043029 by Ake Hedman

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----- Original Message ----- From: "Olin Lathrop" <KILLspamolin_piclistspam.....COGNIVIS.COM>
To: <spam_OUTPICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Wednesday, October 25, 2000 2:51 PM
Subject: Re: [EE]: best way to measure KWH


{Quote hidden}

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2000\10\26@082335 by Chris Eddy

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Ake;

The method that I have used finds the two zeero crosses and subtracts the time.
This example was for telephony, where I had to determine the frequency of ring.
First you run a leaky peak to peak detector.  From this, you set a threshold at
the midpoint.  Then you catch a point before and after both the leading and
falling crosses.  You now have four datapoints on each waveform. Now use the
before and after point on each edge to calculate an interpolated cross point.
Calculate the one for the falling (or rising) on both waveforms and you have
phase.  Calculate T for the rise and fall on one waveform and you have
frequency.


>
>  Using a PIC: How do I measure the phase angle?
>

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2000\10\26@112145 by Andy Howard

picon face
> From: "Bob Ammerman" <RemoveMERAMMERMANRemoveMEspamEraseMEPRODIGY.NET>


> I guess it's a cultural thing.

Yep, it must be. Two nations divided by a common phase.


> In the US we _never_ think of our 220V center tapped ground (ie: two legs
> 180 degrees apart) power as two phase. It is just single phase over here.

I dimly remember in college (in the UK) the US domestic supply described as
two-phase 220v, so that's certainly how Limeys think of it.

If you consider there is the neutral and two other lines each of 110-ish
volts referred to neutral and in antiphase to one another then two-phase
isn't a bad description.  Two-phase derived from a single phase of the
company's 3 phase distribution perhaps, but after the transformer the format
of the original supply is irrelevant really.

Maybe bi-phase would be a better description...:>


> Three phase is wired either delta or wye and has three phases 120 degrees
> apart.

Yep, sqroot(3) and all that stuff.





.

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2000\10\27@150706 by Olin Lathrop

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> Using a PIC: How do I measure the phase angle?

You would have to measure the voltage and current waveforms "many" times per
cycle, like 50 for example.  That's easy enough.

There are many possible ways to compute phase angle.  The simplest is
probably to measure the time lag in the zero crossings.



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Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, KILLspamolinspamspamBeGonecognivis.com, http://www.cognivis.com

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