My smart meter data
- Thread starter gar
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mivey
Senior Member
For larger customers: yes.
gar
Senior Member
- Location
- Ann Arbor, Michigan
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- EE
130106-1322 EST
mivey:
Relative to post #23.
Do these meters assume the voltage is a sine wave, or extract the fundamental voltage component? Then extract the fundamental current component, and use these to determine a fundamental phase shift power factor, and fundamental real power? Then subtract the fundamental current component from the total current to get a non-phase shifted current, and process that for its real and apparent power values?
Relative to post #19.
I also don't believe DTE will do what they want. Therefore some monitor, such as TED, will be needed.
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mivey:
Relative to post #23.
Do these meters assume the voltage is a sine wave, or extract the fundamental voltage component? Then extract the fundamental current component, and use these to determine a fundamental phase shift power factor, and fundamental real power? Then subtract the fundamental current component from the total current to get a non-phase shifted current, and process that for its real and apparent power values?
Relative to post #19.
I also don't believe DTE will do what they want. Therefore some monitor, such as TED, will be needed.
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mivey
Senior Member
Don't know exactly how each one works but they can provide displacement and distortion vars, THD, etc. so they are extracting the fundamental.
I agree. Security is the issue. Down the road I can imagine that each meter can be programmed to have its own multi-level security access but I don't think that is typical now. I will say that we often pick up meter data from other utility meters so security is not perfect. Think about how many do not think to change the default security access code/parameters. As these systems mature, errors like that will be addressed.
The POCO makes use of the total power factor in the sense that it is an arithmetical combination of displacement power factors of each phase in a three phase supply.
For large customers how do they take account of distortion power factor also? Thanks.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
130109-2013 EST
I now have DTE data from most of the days since my smart meter was installed. There are possibly 2 to 4 missing days in about 100 days. The data they are providing can be useful to an ordinary customer. But study and analysis is required on the customer's part. Will customers use the information? Probably not many.
Since I am now getting the smart meter data I have restarted collecting data with TED. An interesting result from the data for 1-8-2013 is that thru the night TED was reading about 10% high compared to DTE. During the day it is more in the 5% high range.
My night time load is almost all single phase induction motors, furnace, and refrigeration, and adds to an average of about 800 W. This same load exists during the day, but now there is more non-phase shifted load added to that base load. Much of this added load will have some bad power factor, but a lot is distortion power factor, and some unity PF.
I know from tests that I have run using the TED system on an unloaded induction motor that that it reads substantially high on power relative to the actual power consumed.
I believe I have previously shared some of this data. For an unloaded 1/3 HP motor actual power input was 139 W, but TED read 186 W. PF was 0.25. At partial power factor correction, PF = 0.62, the power values were 138 W and 152 W. So under loaded conditions, PF will probably be higher than 0.62 and I can't presently measure it, but I certainly can expect TED to read high.
On a pure resistive load TED is relatively close on power calibration. Probably closer than 5%.
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I now have DTE data from most of the days since my smart meter was installed. There are possibly 2 to 4 missing days in about 100 days. The data they are providing can be useful to an ordinary customer. But study and analysis is required on the customer's part. Will customers use the information? Probably not many.
Since I am now getting the smart meter data I have restarted collecting data with TED. An interesting result from the data for 1-8-2013 is that thru the night TED was reading about 10% high compared to DTE. During the day it is more in the 5% high range.
My night time load is almost all single phase induction motors, furnace, and refrigeration, and adds to an average of about 800 W. This same load exists during the day, but now there is more non-phase shifted load added to that base load. Much of this added load will have some bad power factor, but a lot is distortion power factor, and some unity PF.
I know from tests that I have run using the TED system on an unloaded induction motor that that it reads substantially high on power relative to the actual power consumed.
I believe I have previously shared some of this data. For an unloaded 1/3 HP motor actual power input was 139 W, but TED read 186 W. PF was 0.25. At partial power factor correction, PF = 0.62, the power values were 138 W and 152 W. So under loaded conditions, PF will probably be higher than 0.62 and I can't presently measure it, but I certainly can expect TED to read high.
On a pure resistive load TED is relatively close on power calibration. Probably closer than 5%.
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mivey
Senior Member
They measure the harmonic distortion They are not just measuring the fundamentals.
- Location
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- Retired PV System Designer
One way of looking at it is to go back to the formal definition of power factor. You take the actual power, measured by integrating the instantaneous product of the voltage and the current (the way the old mechanical meters did, using what was in effect an analog computer
) and then you divide it by the product of the RMS voltage and the RMS current. As long as you can measure all three of these values, you can get the combined phase shift and distortion power factor in one arithmetic ooperation. Regarding the arithmetical combination of the power factors for three phase, that gets a little more complicated. Going just by the fundamental definition of power factor, you should take the sum of the real power for the three phases and divide it by the sum of the VA values for the three phases. This is not going to be any simple combination of the individual phase power factors. For example, for a balanced load with a power factor of .6 on each phase, the PF of the whole circuit will also be .6. So you may expect that the formula is (.6 + .6 + .6)/3 = .6. But that would be wrong. If the load is a large single phase load with PF of .6 and a very small balanced load with PF=1, the PF on one phase will be .6 and the PF on the other two phases will each be 1, while the PF of the whole circuit will still be very close to .6. You have to weight the phase power factors by the relative power consumed on that phase.
mivey
Senior Member
It gets more complicated in that we are not just summing in one plane but in 3D space. The resulting VA is a vector quantity not in the P-Q plane but in a plane that is rotated in the Q-D plane where D is the Distortion power (D being along the Z axis if we let P & Q be along the X & Y axis).
You can picture that by drawing a diagonal line from the bottom left corner towards the upper right corner of a piece of paper. The horizontal paper edge represents P, the vertical paper edge reresents Q. The paper is in the 2-D space of the desk (our P-Q plane). If we lift the top edge of the paper, we now have a line that is in 3D space and also has a height component, which represents the distortion component of VA.
We call the apparent power U and we have U^2 = P^2 + Q^2 + D^2. Power factor is P/U when we have distortion. For the three-phase case we sum the Ps, sum the Qs, and sum the Ds and solve for the resultant U and then we can calculate P/U for the three-phase system.
Older meters would not calculate VA as a vector quantity but would just arithmatically sum the vector length of the individual phases because it was easier. Digital meters make the easier arithmatic summing method outdated.
mivey:
The real power factor taking into account harmonic distortion is always lower than the displacement power factor. That is one way to distinguish between the two in the gar's recording of power factor values if his meter had the facility to record both. Since he recorded only one set, it is most probably that of displacement power factor.
The real power factor taking into account harmonic distortion is always lower than the displacement power factor. That is one way to distinguish between the two in the gar's recording of power factor values if his meter had the facility to record both. Since he recorded only one set, it is most probably that of displacement power factor.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
130116-1008 EST
Haji:
See Cirrus Logic CS5461A IC datasheet for a discussion of how they measure RMS, apparent power, and real power. This chip is used in the TED system. I don't know what is used in Kill-A-Watt, but I suspect a similar chip.
As I said before if you are going to try to separate out the phase shift power factor for a given load you are going to have to provide some definitions, and then build a special circuit around those definitions. I believe Mivey responded by saying he believed that it would be based on the fundamental components of both voltage and current. This is a more difficult instrument to make compared to one that measures classical power factor (real power/apparent power). There are a number of low cost chips for classical power factor measurement, such as the CS5461A.
I believe that the Kill-A-Watt probably measures classical power factor.
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Haji:
See Cirrus Logic CS5461A IC datasheet for a discussion of how they measure RMS, apparent power, and real power. This chip is used in the TED system. I don't know what is used in Kill-A-Watt, but I suspect a similar chip.
As I said before if you are going to try to separate out the phase shift power factor for a given load you are going to have to provide some definitions, and then build a special circuit around those definitions. I believe Mivey responded by saying he believed that it would be based on the fundamental components of both voltage and current. This is a more difficult instrument to make compared to one that measures classical power factor (real power/apparent power). There are a number of low cost chips for classical power factor measurement, such as the CS5461A.
I believe that the Kill-A-Watt probably measures classical power factor.
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gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
130117-0743 EST
Haji:
I define classical power factor as "real power"/(Vrms*Irms). If by displacement power factor you mean the power factor from a phase shifted current component, such as a capacitor or inductor would produce with sine wave voltage excitation, then classical and displacement power factors are only the same for sine wave voltage excitation and a linear load of capacitance, inductance, and resistance.
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Haji:
I define classical power factor as "real power"/(Vrms*Irms). If by displacement power factor you mean the power factor from a phase shifted current component, such as a capacitor or inductor would produce with sine wave voltage excitation, then classical and displacement power factors are only the same for sine wave voltage excitation and a linear load of capacitance, inductance, and resistance.
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gar:
By displacement power factor, I mean the power factor for fundamental components of voltage and current.
If ,by real power, you mean that it does not include 'power' due to harmonic components, it means the definiton you gave in your last post for classical power factor is the same for displacement power factor.
By displacement power factor, I mean the power factor for fundamental components of voltage and current.
If ,by real power, you mean that it does not include 'power' due to harmonic components, it means the definiton you gave in your last post for classical power factor is the same for displacement power factor.
Last edited:
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
130117-0831 EST
Haji:
Real power means the power resulting from any related voltage and current waveforms. Related means one results from the other. Real power includes power resulting from high harmonic content waveforms.
Apparent power is Vrms*Irms and it is exactly what it says. Separately measured V and I using an RMS instrument on the same load.
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Haji:
Real power means the power resulting from any related voltage and current waveforms. Related means one results from the other. Real power includes power resulting from high harmonic content waveforms.
Apparent power is Vrms*Irms and it is exactly what it says. Separately measured V and I using an RMS instrument on the same load.
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