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True Power Metering

True Power Metering

1) When the voltage and current peak at different times, less than the full voltage times the full current is measured.


2) Added: Besides, PF improvement is not a one-size-fits-all kind of thing. The amount of correction needed must be determined. You don't want to over-compensate for when reactive loads are turned off.[/QUOTE]

1) So, what you're saying is that because the voltage and amperage occur at different points in time, the meter's 'motor' is driven at a rate referenced to the conjunction of their indidvidual sine waves by the real power consumed (delta) rather than the peak values of voltage and amperage? Makes sense... if that's how they work...so what is done in a commercial metering situation to measure peak power usage and PF?

2) Yes, I saw that immediately; and so have felt that devices currently being offered were, at best, quite imperfect. Consequently; being the son of a consummate tinkerer, I began 'pondering' what components would be required to create a dynamic compensatory response to motor-load effects on PF. Turns out the Chinese have a device designed for industrial apps that does just that. Ironically, the same manufacturer sells the 'Power Save 1200' which is a fixed capacitance unit designed for US markets!
 
I really LIKE beer!

I really LIKE beer!

charlie b said:

To start with, power factor does not ?go out of sync.?

Now back to electrical stuff, and a bit of trigonometry.

Power factor is a measure of the angle located at point 1. What would happen to that triangle, if you drew the vertical line as 1/2 inch long, instead of 1 inch? Here again, the real work, line 1-2, does not change. But the apparent power provided by the utility (line 1-3) is now much shorter. Thus, in order to allow the customer?s motors to do the same amount of work, the utility has to provide less power..
Click to expand...


What great word portrayals...I could see that even without the white board!
Previously, in my mind's unguided eye, I was seeing 2 sine waves arranged along a graph where 'x' is representing time and 'y' is representing amplitude: the first wave is voltage; the second amperage. I imagined the point of their conjunction as the value of real power (the liquid beer in the glass) and the 'y-coordinate' distance between that point and their respective peaks as the 'lost power' caused by inductance (the foam). The angle formed by a line from the zero, zero point on the graph to that point of convergence represented the PF angle. Using that model, the solution is to introduce capacitance in a value equal to the 'x-coordinate' of the current wave thereby bringing current and voltage back 'into phase' (reducing PF angle to zero). Although this may not be scientifically corrrect, it seems conceptually representative.
What is at issue is: what does the meter record...and for myself, who has no experience with the internal function of meters...how? My presumption had been that it reads the peak values (which includes the foam) rather than the convergence of waves (just the liquid) and therefore could be improved by PF correction to whatever degree they were divergent (foamy).
For addtional background on the reason for my inquiry see next posting: "WOW"....Thanks!!
 
WOW! Scam or not, IT WORKS!

WOW! Scam or not, IT WORKS!

I am delighted and gratified by this forum's contributors willingness to cure my ignorance, even on a topic which seemed to be a 'dead horse'!
I especially appreciate the patient and thorough explanation of PF by Charlie B. and found Larry B. Fines meter info enlightening.
Thanks to all of you who contributed.

However; I still have an issue to resolve! Let me explain...

The Background:
I recently visited a respected colleague (another assistant to the Lord-High Commissioner) who had installed one of these simple fixed-capacitance 'scams' on his home electrical service about a month before my visit. He had just received his first utility bill since it's installation: 40% savings! Since we both regularly get utility bills in the $800-900/month range, he was pretty excited and encouraged me to look into the equipment and the related business possiblities.
At this point, I should explain that we are both IBEW wiremen, who each at different times, have operated contracting firms for ourselves or others. Together, we have over 60 years in the electrical trade with a high exposure to the technical side of the business including the construction, start-up and commisioning of all systems involved in RUPS 24/7 internet facilities; 'peaker' power plants and the like. So, I think I can say without boasting: neither of us is clueless (despite the fact that he likes to compare our joint testing activities to a pair of incoming unguided missiles)!

On my 8 hour ride home from his place, I had plenty of time to consider his 'testimonial'. First of all, he has lived in this same house for about 5 years with a consistent usage history and, because of his electrical testing skills, should know better than to mistake reduced usage for a reduction in costs. Secondly, like may Southern Californians, he has a pool. a heat pump A/C, numerous ceiling fans, refrigerator, freezer, D/W, washer, dryer...in other words: his power consumption is heavily tipped toward inductive loads.
And thirdly, with this unintelligent fixed-value capacitor set he saved more in his first month than he paid for the 'little grey box'. (Which, by the way, was 15 times what the Chinese charge their US importers!). Since several of his loads run almost continuously, it may be that the capacitors were 'tuned' to his needs and therefore unusually effective...but, what could you get from a dynamically compensating system?! And what would it cost to build?

So this is my issue: how did this happen?
How did my friend save 40% on his utility bill by simply adding some arbitrary value of PF correction to his residential power system?

Anyone?
 
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Ass't Lord-High Commish said:
1) Makes sense... if that's how they work...so what is done in a commercial metering situation to measure peak power usage and PF?
Click to expand...
With CT/PT metering. These are transformer that are clamped or encicle the phase conductors that measure the voltage and current in real time. This allows the POCO to see the phase relationship.
 
Ass't Lord-High Commish said:
I recently visited a respected colleague (another assistant to the Lord-High Commissioner) who had installed one of these simple fixed-capacitance 'scams' on his home electrical service about a month before my visit. He had just received his first utility bill since it's installation: 40% savings!

So this is my issue: how did this happen?
How did my friend save 40% on his utility bill by simply adding some arbitrary value of PF correction to his residential power system?
Anyone?
Click to expand...
I assume that your colleague gets billed in kWh.
Neither fixed nor automatic power factor correction would change the kWh used.
 
081213-1359 EST

A test to perform.

Turn everything off in the house. The watt-hour meter should not change with time.

Connect about 10 ohms across the 120 line. This is about a 1500 watt heater. Measure the watt-hour meter change over a 5 minute period. Record it.

Remove the 10 ohm resistor and in its palce put a 2500 ufd AC adequate voltage rating capacitor. This has approximately 10 ohms capacitive reactance at 60 Hz. Now do the watt-hour measurement for 5 minutes. Record it.

Compare the results. The capacitor is almost a pure reactive component. I do not know what results you will get. I know what should be expected. I have not run the experiment. Also I do not know where it is easy to get the capacitor for your experiment.

Do you have a rotating disk type of watt-hour meter or is it electronic?

.
 
Sorry to burst your bubble Ass't Lord-High Commish, but...

Sorry to burst your bubble Ass't Lord-High Commish, but...

When he says to you that he "saved 40%", did he tell you that his kWH went down by 40% or the dollars went down 40%? In SoCal, you are probably around $0.18/kWH am I right? If he was spending $900 per month, that is 5000kWH / month! That, my friend is a LOT of electricity. SCE has a complicated 5 tiered rate system, starting with a baseline of just 16.5kWH / day, or about 495kWH / mo. So at 10x the baseline, you and your friend are pushing well above the 5th tier (3X baseline use) of pricing every month. The $ value of penalties you are paying is going to be enormous by comparison to most people, so in that case, leaving off just one appliance or reducing even a little energy use in any given month can make a big difference.

So here is how I have seen it work. He noticed that he was parting with a LOT of cash every month to the utility, he decided to do something about it. Nobody wants to cut back, that is a "negative action", so he searched for a "positive action" he could take instead. Your friend buys this magic box, he feels good about himself. Meanwhile, subconsciously he knows what he really needs to do and does it without thinking. He uses less; raises the AC thermostat a degree or two, loads the dishwasher more before running it, washes and drys clothes in bigger but fewer loads, turns off the ceiling fans when he leaves the house, etc etc. Because he was in such an extreme penalty situation with the utility, those small subtle changes make a big difference. But because he bought that worthless grey box, he attributes it to that.
 
I'm not sure if this angle has been taken, and maybe one of you PE's could set me straight...

If the normal, "old school" meter works as mentioned, would not corrected / hi PF actually cost the home owner more? Because... 1. not all loads are inductive/reactive 2. (as mentioned) that Cap's do draw some power.

Basically doesn't the homeowner "cheat" the Poco, with hi PF, and because the Poco knows this charges accordingly, and so then by cleaning things up, you are then paying more, because you are letting your meter run more efficiently?



Doug S.
 
From what I have been told by those ECs who have installed them, they are not UL listed or an approved device, therefore illegal to install.
 
081214-0911 EST

Doug S:

If by "old school" meter you mean the electro-mechanical spinning disk type, then this device measures power integrated over time, energy. One can store energy or dissipate it. Here power means heat, mechanical work, or some form of energy that is not electrical.

If you pass a current thru a resistor you change the electrical input energy to heat output energy. Exactly what went in comes out. To get this energy back into an electrical form you would need some conversion device such as a steam engine and generator.

If you feed a current into a capacitor you put a charge into the capacitor and you store energy in the capacitor in an electrical form. In an ideal capacitor there are no resistive losses (heat) and therefore no energy transfer to some other form of energy than electrical. Theoretically all that electrical energy stored in the capacitor can be output as electrical energy.

What the spinning disk watt-hour meter does is to measure the accumulated average energy that flowed thru the meter into loads that converted electrical energy into non-electrical energy, ultimately into heat. The true inductive and capacitive portions of the loads, no heat loss, do not cause any accumulative reading of the watt-hour meter.

Motors are a combination of resistive, inductive, and in some capacitive current components. Single phase motors often times have a capacitor for phase shifting to one coil.

The resistive component results from internal power losses, heat generated in the motor, and the physical mechanical load on the motor.

The inductive, and/or capacitive components are those that store electrical energy as electrical energy and feed it back to the system each cycle. This instantaneous energy transfer does not accumulate on the watt-hour meter.

Ideal capacitors do not convert electrical energy into heat. Real capacitors come very close to being ideal capacitors, and dissipate very little heat.

In your statement
2. (as mentioned) that Cap's do draw some power.
Click to expand...
I do not know what you mean by power. Is it the heat loss or the instantaneous electrical energy?

Basically doesn't the homeowner "cheat" the Poco, with hi PF, and because the Poco knows this charges accordingly, and so then by cleaning things up, you are then paying more, because you are letting your meter run more efficiently?
Click to expand...
There is no cheating.

The energy consumption of your watt-hour meter is minuscule compare to the amount of energy you use and thus the efficiency of that meter is of no concern.

Fundamentally the power company buys fuel, equipment, and labor. These all cost money. The power company supplies energy to you the customer. There is derived a cost of the entire system to operate and you pay some small part of this based on how much of those resources you used. Those resources are measured by your watt-hour meter.

If you have a purely resistive load on the system then your cost to the system is your load, the distribution losses, the generation losses, thermal to electrical efficiency, and plus overhead. If you put no load on the system then the cost is overhead. The system is designed to be as efficient as is practical. This means maybe 5% electrical loss (distribution and generation), and thermal conversion efficiency may be 40% (I am not in the business so I do not know) which means 60% loss.

If you use no current from the system you pay nothing in most areas. So the power company is at a loss because of overhead. If you have a resistive load they make a small profit (I left that out of the above equation). If you put a purely reactive load (capacitor or inductor) on the system, then the power company has a loss because you pay nothing but your reactive load costs them distribution losses, generation losses, thermal to electrical losses, and overhead.

The rate you pay per KWH is derived by an estimate of your cost to the system derived from some averaging method moderated by the public service commission.

Capacitor run single phase motors are not too bad on power factor. A number of motors in a home may be of this type. A lot of energy consumed in a home is pure resistance. Stoves, ovens, dryers, and incandescent lamps.

As you drive around you will see power factor correction capacitors on poles. So actually the power company does do some average correction to reduce their distribution and generation losses from inductive loads.

.
 
Okay, so one of these guys is at our home show, he has the power going through the electric meter to a motor pulling 6A. The meter does one rotation in 120 secs. He turns on the KVAR device and the meter spins at 134 secs. What am I missing? The voltage stayed the same and the amps dropped to about 1.5A.
 
Wizard of OZ:

Wizard of OZ:

rich000 said:
Okay, so one of these guys is at our home show, he has the power going through the electric meter to a motor pulling 6A. The meter does one rotation in 120 secs. He turns on the KVAR device and the meter spins at 134 secs. What am I missing? The voltage stayed the same and the amps dropped to about 1.5A.
Click to expand...

Remember the scene where Toto reveals the Wizard behind the curtain? More of the same here.

First, assuming a meter constant, Kh, of 7.2. Power would be,

P = Kh/2min = 7.2WH/(0.033hr) = 216W
Pa = 6A x 120V = 720VA
PF = 216W/720VA = 0.3

After switching in the caps,

P = 7.2WH/(.037hr) = 195W
Pa = 1.5A x 120V = 180VA
PF = 195W/180VA = 1.1--can't be

I suspect they have set up this demonstration with a poor power factor. Then the change in current is dramatic, but the change in real power is zero (considering experimental error), and that is what is important.
 
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Jraef said:
When he says to you that he "saved 40%", did he tell you that his kWH went down by 40% or the dollars went down 40%? In SoCal, you are probably around $0.18/kWH am I right? If he was spending $900 per month, that is 5000kWH / month! That, my friend is a LOT of electricity. SCE has a complicated 5 tiered rate system, starting with a baseline of just 16.5kWH / day, or about 495kWH / mo. So at 10x the baseline, you and your friend are pushing well above the 5th tier (3X baseline use) of pricing every month. The $ value of penalties you are paying is going to be enormous by comparison to most people, so in that case, leaving off just one appliance or reducing even a little energy use in any given month can make a big difference.

So here is how I have seen it work. He noticed that he was parting with a LOT of cash every month to the utility, he decided to do something about it. Nobody wants to cut back, that is a "negative action", so he searched for a "positive action" he could take instead. Your friend buys this magic box, he feels good about himself. Meanwhile, subconsciously he knows what he really needs to do and does it without thinking. He uses less; raises the AC thermostat a degree or two, loads the dishwasher more before running it, washes and drys clothes in bigger but fewer loads, turns off the ceiling fans when he leaves the house, etc etc. Because he was in such an extreme penalty situation with the utility, those small subtle changes make a big difference. But because he bought that worthless grey box, he attributes it to that.
Click to expand...

Yessir! 5000kwh is a tremendous amount of electricity! Maybe he turned off two or three of his grow lamps to save his 40% :grin:
 
rich000 said:
Okay, so one of these guys is at our home show, he has the power going through the electric meter to a motor pulling 6A. The meter does one rotation in 120 secs. He turns on the KVAR device and the meter spins at 134 secs. What am I missing? The voltage stayed the same and the amps dropped to about 1.5A.
Click to expand...

Fine and good, but amp drop is inconsequencial. That's like someone trading in their 120v appliances for 240v with the idea that it will drop their utility bill. 1000 watts at 120 volts pulls approx. 9 amps. 1000 watts at 240 volts pulls approx. 4.5 amps. You can change the voltage and ampreage, but watts are watts, and you get billed by watts consumed, not volts or amps.
 
rich000 said:
Okay, so one of these guys is at our home show, he has the power going through the electric meter to a motor pulling 6A. The meter does one rotation in 120 secs. He turns on the KVAR device and the meter spins at 134 secs. What am I missing? The voltage stayed the same and the amps dropped to about 1.5A.
Click to expand...
It depends on what type of product he was showing you.

There are essentially two kinds of scams going on out there with regards to "magic boxes" that will save energy. One is the Power Factor Correction Capacitors, which is what this thread was originally about. Those do NOT save energy, as has been discussed in this thread. The other is a "Power Factor Controller", a.k.a. "Nola Energy Saver", a.k.a. "Energy Optimizer", a.k.a. "Power Miser", "Green Plug" blah blah blah. Every one of them claims that THEY have the super secret formula, and NOBODY ELSE'S does.

These things are all based on what is actually called a Nola Power Factor Controller. Contrary to the name, it does not control power factor but it uses the measurement of power factor to control voltage going to an induction motor. By lowering the voltage, you lower the iron losses in the motor because those losses are based on the applied voltage. You ALSO reduce the motor torque of course but the theory is, by monitoring the power factor you can tell when the motor is UNLOADED. If it is unloaded, you no longer need the torque, so if you lower the voltage to reduce the iron losses, it doesn't matter that you lost torque because you didn't need it. Confusing? Not really, but it takes a bit of thought to put it all together.

So here's the catch. First off, in order for it to save anything the motor has to be unloaded. One of the tricks they do in the demos is to use a completely open shaft (uncoupled) motor. This immediately gives the demo the maximum possible benefit. The second issue is, older 1 phase motors are notoriously inefficient. So again, they often "pad" the demo by using as old of a 1 phase motor as they can find. They actually search out and find the most inefficient motor they can. In reality, motors like that are usually made for some special purpose where inefficiency is irrelevant compared to the duty at hand. An example would be a grinder motor. If it is only on for a few minutes to do a simple task, it would be more important to get it up to speed faster than it would be for it to run economically. So the demo is essentially rigged to demonstrate the absolute best that the technology can offer. But here is the problem; when is a running motor ever running completely unloaded? If it was, why is it running at all? Why not just turn it off? The answer is, you can! There is no better energy saver than the Off switch. The scam then is to show you something that is true, as in the grossly inefficient motor running open shaft, and get you to believe that the same phenomenon will translate to YOUR application. It rarely does.
 
rich000 said:
What am I missing?
Click to expand...
For your house you pay for kWh, not kVAh. The difference between kW and kVA is the power factor. By reducing the power factor, the kVA is lowered to a value closer to the kW. If you're already paying based on kW then why do you need a device to lower the kVA in your house? You're only going to lower kW by turning stuff off.

How often do you run large motors in your house? What does this device do to your house's electrical system when motors are not running. The device is always on. Anything that is 'on' will consume some amount of energy. Even a couple watts always 'on' can add up to a couple dollars in the course of a year.
 
I understand the kw vs kva and I understand the lower amps higher pf deal. What I don't understand is how the darn meter can spin slower.

It is a capacitor bank and I asked about what is the power draw of the bank when the motor is not running and he said it doesn't draw any power.

As I said I plan on running my own controlled test. I will update you in a couple weeks.
 
rich000 said:
What I don't understand is how the darn meter can spin slower.
Click to expand...
How can you be certain what type of meter was used in the demonstration? If you do a test on your own, you will be able to select the test equipment such that it accurately models a residential application.
 
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