I was going through the Xeto specs and noticed that we have power factor units listed as “%”. xeto spec

I understand that some people view power factor that way, but I believe it to be incorrect.

Power factor is the ratio of real power/apparent power or the cosine of the angle between voltage and current. Cosine always produces an output -1 to 1 (not a percentage).

Wikipedia says: "power factor is by definition a dimensionless number between -1 and 1."

The international standards groups IEC and IEEE both use -1 to 1.

• IEC uses the decimal format (0.80) in its standards example
• IEEE also uses the decimal format (0.866) in its standards example

Using "%" for power factor is also inconsistent with the units database (unit db) where we have:

-- dimensionless --
power_factor,pf

I also took a look at how 4 building submeter companies handle this:

• Siemens: 0 to 1 (no units). (ref page 108)
• Schnieder Electric: it seems that this may be a source of the percentage issue. They allow a number between -1 and 1 or as a percentage from -100% to 100% (ref)
• Eaton: -1 to 1 (no units) (ref page 89)
• Veris: 0 to 1 (no units) (ref page 24)

I recommend that we update the spec for power factor points to either not include a unit or use the existing "pf" unit.

Hi Keith,

Thanks for feedback.

I agree we should have the power factor specs default to being in the range of -1 to 1 without units. I mistakenly used the "%" units when I made those Xeto specs and I will make that change.

While we are on this topic, do the items below make sense?

• Angle of voltage and angle of current specs have default units in "deg" and may be negative. (Note: Sometimes in practice this angle is referred to as leading or lagging.)
• THD of voltage and THD of current have default units in "%" units in the range of 0% to 100%.
• Voltage imbalance and current imbalance are measured in "deg" units. (If so, then I also need to make updates for this)

THD = Total harmonic distortion

Does anyone else have feedback on these ideas?

• Agree that PF should be unitless
• Angle is typically expressed in degrees, but in theory could be in radians; is there a way to set a family of units ("angle" units) rather than just degrees?
• THD can also be unitless but is typically expressed in percent; recommend normalizing on percent
• Voltage and current imbalance (or "unbalance") is expressed in percent: see this explanation of the math

Hi Stephen, thanks for the feedback.

We will update the PF specs to be unitless.

As of now we model the imbalance and THD specs associated with voltage and current using percent units and probably we will keep it that way. I have not dealt with voltage and current imbalance before and appreciate the explanation.

Let's defer to Brian on if we can set a family of units rather than just degrees.

Also, feedback from others on these topics is welcome.

The earlier feedback from Keith and Stephen has been applied. Thanks again for their support!

However, today Project Haystack still does not clarify what negative or positive power factor (pf) means exactly.

We discussed this before and how we might not want to because of the following different electric meter implementations:

1. Negative pf is for exported power. Positive pf is for imported power. (Or perhaps negative pf is for imported power and positive pf is for exported power?)
2. Negative pf means that the current leads the voltage. Positive pf means that the current lags the voltage.

After more thought I think we should adopt (2) for Project Haystack’s normalization of pf. This aligns with Keith’s earlier comments that power factor is the cosine of the angle between voltage and current. Also, it helps normalize data from various meter implementations so that other application logic does not need to, which is the intention of Project Haystack.

In the case of (1) I believe two data points would need to be modeled – one for the manufacturer specific data point and one for the Haystack normalized data point that is a computed point based on the manufacturer specific data point. It would be important that the manufacturer specific data point does not have tags necessary for the Project Haystack normalized data point.

How does this proposal sound to the community? Does anyone foresee a problem trying to normalize (1) to (2)?

Thanks!

Here are some more ideas which I am sharing on behalf of Rob Patterson who works at Miller Electric. (Thanks Rob!)

A relevant article from Schneider Electric on this topic can be found here.

Should Project Haystack normalize on the IEEE or IEC definition for power factor described in the link above? Or should we allow for both?

If the target market is for the USA, then we should probably just use the IEEE convention. However, I suspect integrators in Europe will want better support for the IEC definition of power factor.

Considering that at least some meter implementations allow for either convention for power factor, we might want to do the same in Project Haystack.

Rick,

I prefer to use the IEC definition as this is worldwide used. Also materials like circuitbreakers with IEC approval are tested according a norm 60947. And in these norms are all the definitions of pF V or I wirtten. I have never seen a circuitbreaker IEEE approval. To be honest the IEEE has also a political side with their Strategic Plan IEEE fosters technological innovation and excellence for the benefit of humanity.

I vote for the IEC model for 3 main reasons.

Reason 1 - This decision should probably be based around the “normal” situation.

99+% of our metering operates in quadrant 1. (Building loads are inductive in aggregate.) I have never noticed a negative pf on any of it.

Has anyone?

Does anyone use a product that produces a negative pf with positive kw and positive kvar?

Does anyone have a meter that shows a negative Apparent Power or negative kVA? (More on this below)

The IEEE power factor in Q1 is negative -> It does not follow the “normal”.

Reason 2 – IEC supports common math

What functions are used to describe power factor, apparent power, active power and reactive power? (are any of these wrong?)

• apparent power = voltage * current
• power factor = cos θ
• active power = apparent power * power factor
• reactive power = apparent power * sin θ

None of this works with the IEEE model.

In several places, power factor is defined as the cosine of the angle. In the IEC model, this angle starts at 0 on the axis between quadrants 1 and 4, and then moves counter-clockwise. The IEEE model does not support this function as the polarity of power factor changes between every quadrant (conflicts with the cosine function).

Reason 3 – I don’t recognize a basis for the IEEE model

(This list started with 2 reasons, but as I looked at this more, the more the IEEE model doesn’t make sense… and that may be my limitation)

In IEEE, is apparent power negative in quadrants 1 and 2? I could see and argument for having apparent power be negative in quadrants 3 and 4 OR quadrants 2 and 4. In this IEEE paper, https://ieeexplore.ieee.org/document/9144596, it defines power factor as real power divided by apparent power… to have a negative power factor in Q1, apparent power has to be negative.

In quadrant one, both standards have reactive power and real power being positive… how can power factor be negative? What drives this?

Sources:

• https://www.progress-energy.com/assets/www/docs/business/power-factor-how-effects-bill.pdf
• https://control.com/technical-articles/active-power-reactive-power-apparent-power-and-the-role-of-power-factor/
• https://www.electronicdesign.com/technologies/test-measurement/article/21200794/how-to-measure-power-factor-a-tutorial
• https://ieeexplore.ieee.org/document/9144596

Hi Frank and Keith, thanks for sharing. You both make compelling reasons to normalize on IEC.

We are seeing Project Haystack use cases expand into Battery Energy Storage Systems (BESS), which we should be considering.

Let me try to make the case for IEEE defined pf.

• For IEC, the power factor sign is only dependent on the direction of active power flow, which would already be known information if import or net active power were being monitored (which is reasonable to expect I think).
• IEEE conveys new information: Is the load leading or lagging? If this information is not conveyed with the pf data point, then additional data points would likely be required to answer this question.

By taking the absolute of the IEEE pf and using info from the import or net active power data point, the IEC pf can be derived from the IEEE pf.

Here are questions I think we would want to answer before settling on support only for IEC pf:

• What data points would convey the load was leading or lagging? Would just the angle of current data point convey that?
• Would those data points have been used by a typical integrator if the IEEE pf was used?

IEC pf would plot nicer than IEEE pf. In an ideal world we would model voltage and current as complex numbers but I realize most meters probably don’t support that.

I think to consider IEEE we would need to find a meter, in common use, that expresses pf as negative in Q1.

What data points would convey the load was leading or lagging? Would just the angle of current data point convey that?

You can always determine the quadrant with kw and kvar (assuming they have the appropriate sign). They are the (x,y) of the system. Simply make a function that is

isNegative(kw/kvar)

Would those data points have been used by a typical integrator if the IEEE pf was used?

2-parts

• The “typical integrator” doesn’t understand kw vs kVA vs kVAr vs pf, or care (I would expect less than 5% of non-electrical engineers have any interests in these concepts)… and there really isn’t a ton of use for all of them outside of specific applications.
• When there is an opportunity to integrate with all 4 of them, they all will be pulled in.

IEEE-world question

What is the relationship between apparent power, active power, reactive power and power factor?

Is apparent power sometimes negative?

What does the vector structure of these relationships look like?

Thanks for sharing Keith.

So you would use kVAR to determine leading or lagging power factor. The case for IEEE might be you just need IEEE pf and active power, which would mean a reduction in the required point count. Also, some other analytical functions might be simpler from needing to work with fewer points.

What does the vector structure of these relationships look like?

Agree, this is a question we would need to answer. I will see if I can find a mathematical derivation for IEEE defined power factor.