v4 meter VAR phase - missing for high PF?

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jcb
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v4 meter VAR phase - missing for high PF?

Post by jcb »

Background: I have two V4 units one on service entrance one on solar inverter

V4 unit on solar system reports significant VAR, about 8% of watts, so for 6KW solar I have near 500VAR (a significant value) . Under these conditions effective PF is rounded off to 1.00 (it is about 0.996) in the V4 report.

I have noticed that the phase indicator perfix for PF (COS) appears to get removed once PF (COS) field hits 1.00.

Problem as I see it: VAR values with unknown phase cannot be combined to find net consumption side VAR.
I have service and solar EKM units, it should be possible to do the math to find consumption side VAR (in an analogous fashion to finding the consumption side watts with the augmented information of the "current direction" field)

If you can report VAR magnitude there must be a phase known for it within the V4. Removing VAR phase information because significant digits of PF have been maxed out does not sound at all correct to me.

Please tell me if I am missing something (I see no other place where VAR phase can be obtained than the PF prefix)

Or alternatively I request that VAR phase be made available (not filtered out of the PF/COS field) so that accurate calculations can be enabled - firmware upgrade?

thanks
Jameson
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Re: v4 meter VAR phase - missing for high PF?

Post by Jameson »

Hi jcb,

Still working on the Centos Linux issue here by the way...

I will try and dive in here the best I can. VARs are not my strong suit either :roll:

I think we may be on different pages. Please define what you mean by "phase" in reference to VARs. To me each phase in an electrical system has to do with the hot lines. In a 120/240 volt 3-wire system (2 hots and a neutral) this would be 2 phases (though it is commonly referred to as single phase). The v.4 meter return VARs on each line (Reactive Power on each phase) and all lines combined (Total Reactive Power on all phases).
I have noticed that the phase indicator perfix for PF (COS) appears to get removed once PF (COS) field hits 1.00
When you say "phase indicator" do you mean the L and C indicators? L0.99 for example?

A perfect Power Factor (1.00) is when the voltage sine wave and the amperage sine wave are in perfect alignment on top of each other. When the voltage and amperage sine waves are off of each other then you have less than perfect Power Factor. When voltage is leading amps it is considered leading (Inductive or L), when voltage is lagging amps it is considered lagging (Capacitive or C)

Are you wanting to know if your real-time VARs are Inductive or Capacitive?

Thanks,
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371
BlueHornet
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Location: Victoria, Australia

Re: v4 meter VAR phase - missing for high PF?

Post by BlueHornet »

I have noticed that the phase indicator perfix for PF (COS) appears to get removed once PF (COS) field hits 1.00
Correct the current is neither leading nor lagging the voltage and the PF is considered to be "In Phase" and at UNITY when 1.00 appears.

I should add, that frequency will also have a bearing on PF in a capacitive circuit.
When voltage is leading amps it is considered leading (Inductive or L),
Partly Right but misleadingly Incorrect

When voltage leads current that means that current is lagging voltage which is an Inductive Load. Inductive Loads always LAG they never lead! This is due to the nature of Inductive circuits and their ability to heavily load a circuit by dropping a voltage directly proportional to the rate of change of current..
when voltage is lagging amps it is considered lagging (Capacitive or C)
Partly Right but misleadingly Incorrect

When voltage lags current that means that current is leading voltage which is a Capacitive Load. Capacitive Loads always LEAD they never lag! This due to the nature of Capacitive circuits and their ability to oppose changes in voltage by drawing or supplying current as they charge or discharge to the new voltage level.

"ELI the ICE man." ELI - Current(I) lags Voltage(E) with Inductive Load(L). ICE - Current (I) leads Voltage (E) with Capacitive Load (C)

In a circuit with only an inductor and an AC power source, there is a 90 degree phase shift between the current and voltage - the current lags the voltage by 90 degrees. This is the ELI part...with the Voltage - EMF (E) an Inductor (L) and Current (I) is LAGGING or behind the EMF

In a circuit with only a capacitor and an AC power source, there is also a 90 degree phase shift between the current and voltage - the current leads the voltage in this case. This is the ICE part...with Current (I) is LEADING or in front of a Capacitor (C) and the Voltage - EMF (E)

Now by definition "Power Factor" is a dimensionless number between -1 and 1(or as some prefer 0 & 1) but as Power Factor = cos [arc tan (X)/(R)] and it can be either leading or lagging, but it will always be positive, because the impedance angle can only be in the 1st or 4th quadrant and the cosine of any angle in the 1st or 4th quadrant will always positive.

Impedance Angle = arc tan X/R
Where: X = Xl +(- Xc)
Note that: (Xc) Capacitance has been designated as a negative and (Xl) Inductance has been designated as a positive
Therefore;
If Xc > Xl then X is negative and the impedance angle is in the 4th quadrant (between 0 and -90).
And if Xc < Xl then X is positive and the impedance angle is in the 1st quadrant.(between 0 and +90).

It is important to understand that the impedance angle can never be in the 2nd and 3rd quadrant.

A Power Factor of less than 1 (one) essentially means that the current and voltage waveforms are not in phase with each other.

A Leading Power Factor means that the current leads the voltage, the load is essentially capacitive and indicated with a -ve (negative) sign or C for Capacitive.

A Lagging Power Factor means that the current lags the voltage, the load is essentially inductive and generally indicated with a +ve (positive) sign or L for Lagging.

A Unity Power Factor ( Unity or 1.00) occurs when the current and voltage waveforms are in perfect synchronization or "In Phase" they are neither Leading (capacitive) nor Lagging (Inductive) and could be best described as being a Resistive Load, however, if the inductive load of a motor or transformer is completely balanced out by a capacitive load or vice versa, a maximum power factor of Unity will also result.

For example a negative power factor (capacitive) of between 0 and -1, could be the result of returning power to the grid. Take for instance the case of a building fitted with solar panels and inverter, this would occur when the power being generated is not being fully utilized by loads within the building and the surplus is being fed back to the grid.

With respect to "var" question:
The unit "var" (volt-amp reactive) is the unit by which reactive power is expressed, this could be inductive, capacitive or a combination of both and could also include resistance. It is this "imaginary" or reactive power that essentially regulates the voltage in a system whilst Real or True Power is what is what is used to supply energy to a motor, transformer, light globe, PC in fact any electrical appliance and perform the actual work . The combination of Reactive Power and True Power is called Apparent Power (Volt-ampere or VA) and is the product of a circuit's voltage and current, this also does not have any reference to phase angle.

The SI (International System of Units) practice is not to include any information about the type of power (in this case Inductance, Capacitance or Resistance or any combination thereof) in the unit name.
Last edited by BlueHornet on Sat Aug 22, 2015 3:36 pm, edited 2 times in total.
Jameson
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Re: v4 meter VAR phase - missing for high PF?

Post by Jameson »

Thanks Bluehornet,

I appreciate what you have here, that is some good info. The more I grasp power factor and VARs as a concept the more questions I have!

I have this Mnemonics, from wikipedia: https://en.wikipedia.org/wiki/Power_factor which is exactly the opposite of yours. I would appreciate it if you could set the record straight (because I dont know which is correct to be honest). Here it is:

CIVIL: in a capacitive load (C) the current (amps or i) leads voltage (V), voltage (V) leads current (i) in an inductive load (L).

We tend to represent Power Factor as: 0 C to 1.00 (in the middle) to 0 L like this widget from encompass.io:
Screenshot 2015-08-21 11.55.31.png
Screenshot 2015-08-21 11.55.31.png (20.76 KiB) Viewed 19816 times
Let me know if this fits with your understanding or if there is a better visual representation.

For VARs:
I would imagine that if you have a reverse direction of current on Line 1 that and VARs you measure on Line 1 would be reverse VARs.
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371
BlueHornet
Posts: 56
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Location: Victoria, Australia

Re: v4 meter VAR phase - missing for high PF?

Post by BlueHornet »

CIVIL: in a capacitive load (C) the current (amps or i) leads voltage (V), voltage (V) leads current (i) in an inductive load (L).
Mnemonics can be a PIA at times but in a sense yours and mine are identical and not at all opposite: Current Leads Voltage in a Capacitive Load.

Where the confusion sets in here is where it says: Voltage Leads Current in an Inductive Load when what it should be saying is Current Lags Voltage in a Inductive Load that there is no misunderstanding as which leads and which lags, essentially they can't both Lead just by changing the position of the Voltage.

Your original post was misleading for the fact that you stated that Inductive Loads were Leading and Capacitive Loads were Lagging when in fact they are they behave in the exact opposite. Inductive Loads LAG whilst Capacitive Loads LEAD.

With the Voltage reference point at 0 (zero) current either Leads or Lags Voltage. The only quantity that Leads or Lags is Current and it Leads and Lags in reference to Voltage.

This is best represented by the following diagram:
ELI the ICE man.gif
ELI the ICE man.gif (18.82 KiB) Viewed 19812 times
We tend to represent Power Factor as: 0 C to 1.00 (in the middle) to 0 L like this widget from encompass.io:
Screenshot 2015-08-21 11.55.31.png
Screenshot 2015-08-21 11.55.31.png (20.76 KiB) Viewed 19812 times
I see nothing wrong with this! I think it's a reasonably fair representation of what is occurring in a circuit.

If we were to represent L on the right hand side as Inductive Loads then that would be represented with a +ve symbol which is what what an Inductive Load is considered and C on the left hand side being the Capacitive Load would be -ve symbol.
For VARs:
I would imagine that if you have a reverse direction of current on Line 1 that and VARs you measure on Line 1 would be reverse VARs.
This would depend on what Line 1 was measuring. If it were Net Metering a co-generation system, it would depend on the PF of the generation equipment (inverter, wind turbine etc...) and the PF of the Load/s within the building. The var reading may or may not be reversed, they could be aggregation of the vars seen at the generation equipment and the building load depending on their state at the time.

Here are some examples that I captured from a V 4 meter:

Single Phase 240Vac 50Hz Co-Generation System using a Solid State Transformerless Inverter:
L1 - The meter on the left hand side is Net metering the Import & Export of the Co-Generation System
Green = Exporting, Red = Importing, Black = Inverter Power Only is being used
L2 - The meter in the middle is metering the Total Consumed Power Only (Either Imported or Generated Power or a combination of both)
L3 - The meter on the right is purely metering Generated Power
The vars is in the top left hand corner of each meter
VAR 1.png
VAR 1.png (26.49 KiB) Viewed 19797 times
Dang - for some reason I can't add more than 3 attachments, See the posts below for the screenshots.

These questions are getting harder to answer as they become more complex and will likely lead to more confusion (these are topics that are hard to keep simple as they involve multiple variables and introduce other factors such bi-directional power etc...), as we start to get into calculations in the 2nd & 3rd as well as the 1st & 4th quadrants, however, if anyone can shed further light on this topic, I'm more than happy to listen and stand corrected for any errors.

OK, so here is what I have determined with the "imaginary" or as we know it reactive power. Reactive power has no flow of any kind, therefore there can be no direction either, the unit is however useful in the analysis of electrical systems when used in conjunction with VA, W & PF.

Reactive power is always on the y axis and does not fall into any quadrants, therefore it does not lag or lead but can be considered to be delivered or received.

By Delivered I mean that when the Reactive Power (vars) moves (flows) from the “Power Source” through the metering point and into the “LOAD” it is considered as being DELIVERED. Therefore when the Reactive Power is being supplied by the “Power Source” into the load it is referred to as Delivered Reactive Power (vars) and theoretically speaking will have a +ve sign.

When the Reactive Power (vars) moves (flows) from the “LOAD” through the metering point and into the “ Power Source” it is considered to be RECEIVED. Therefore when the Reactive Power is being supplied by the “LOAD" back into the "Power Source" it is referred to as Received Reactive Power (vars) and theoretically speaking will have a -ve sign.

The sign of reactive power movement (flow) may be considered arbitrary.
BlueHornet
Posts: 56
Joined: Fri Dec 16, 2011 10:42 pm
Location: Victoria, Australia

Re: v4 meter VAR phase - missing for high PF?

Post by BlueHornet »

Here are some examples that I captured from a V 4 meter:

Single Phase 240Vac 50Hz Co-Generation System using a Solid State Transformerless Inverter:
L1 - The meter on the left hand side is Net metering the Import & Export of the Co-Generation System
Green = Exporting, Red = Importing, Black = Inverter Power is being consumed by the Load - No Importing or Exporting is taking place.
L2 - The meter in the middle is metering the Total Consumed Power Only (Either Imported or Generated Power or a combination of both) Always Red when Load is consuming power
L3 - The meter on the right is purely metering Generated Power (Green = Generation whilst Black = NO Generation)

The vars is in the top left hand corner of each meter

Call this as "vars" Received - The inverter is in a capacitive state and the load cannot absorb the reactive power so it is sent to the Grid even though we importing power at the time.
VAR 1.png
VAR 1.png (26.49 KiB) Viewed 19797 times
The inverter and the load are in a capacitive state and the combined reactive power from both is sent to the grid or is it?
There is no importing or exporting here, the load is consuming 100% of the generated power.
VAR 3.png
VAR 3.png (30.95 KiB) Viewed 19797 times
The inverter and the load are in a slightly capacitive state and the combined vars are sent to the grid with the power being exported
VAR 7.png
VAR 7.png (31.11 KiB) Viewed 19797 times
Last edited by BlueHornet on Sat Aug 22, 2015 7:03 pm, edited 2 times in total.
BlueHornet
Posts: 56
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Re: v4 meter VAR phase - missing for high PF?

Post by BlueHornet »

VAR 8.png
VAR 8.png (31.03 KiB) Viewed 19797 times
VAR 11.png
VAR 11.png (31.89 KiB) Viewed 19797 times
Here the inverter is in a slightly capacitive state while the load must be in a slightly inductive state.
The inverter line (L3) is showing 48 var of which 24 are being absorbed by the load and the other 24 are being sent to or received by the grid.
VAR 12.png
VAR 12.png (31.52 KiB) Viewed 19797 times
Last edited by BlueHornet on Sat Aug 22, 2015 6:24 pm, edited 1 time in total.
BlueHornet
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Joined: Fri Dec 16, 2011 10:42 pm
Location: Victoria, Australia

Re: v4 meter VAR phase - missing for high PF?

Post by BlueHornet »

Here the inverter (L3) shows 0 vars (theoretically "in phase") yet the load (L2) shows 42 var and the Net meter (L1) shows 40, allowing for a small anomoly of 2 vars and the fact that all the PF are showing 1.00 or Unity you cant tell if the Load (L2) vars are inductive or capacitive, but most likely to be inductive in this case.
VAR 13.png
VAR 13.png (32 KiB) Viewed 19797 times
Can you see what is happening here?
VAR 14.png
VAR 14.png (31.94 KiB) Viewed 19797 times
And can you see what is happening here?
VAR 15.png
VAR 15.png (31.65 KiB) Viewed 19797 times
jcb
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Re: v4 meter VAR phase - missing for high PF?

Post by jcb »

Thank you BlueHornet for taking the time and having the patience to explain the electrical engineering.

Jameson: My original question remains:

Restating: If the v4 meter does not report "capacitive" or "inductive" VAR then there is no way to do the correct VAR calculations in the two meter scenario; V4 meter on service entrance, V4 meter on inverter, with net consumption left to calculation. As explained by BlueHornet:

"all the PF are showing 1.00 or Unity you cant tell if the Load (L2) vars are inductive or capacitive, but most likely to be inductive in this case."

It is the "most likely" above that I consider an issue; guesswork instead of reported data. Rather than being simply a pedantic point of contention having correct VAR data available is valuable; for example analyzing VAR can yield information on the number (of operating) and load state of motor driven equipment such well pumps, refrigeration (heat pump) etc.

Such calculations are enabled for "real" power by virtue of the (real power) "current direction" indicator. The distinction between inductive and capacitive VAR can be viewed exactly analogously to real power forward/reverse, with the indicator being the "C" or "L" part of PF.

If the C/L is not blanked out at indicated "1.00" that will solve the problem. I say "indicated" because clearly power factor is being rounded off due to output reporting precision limits, not due to fundamental internal data precision limits.

A simple firmware change ought to take care of this.

Any chance?
Jameson
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Re: v4 meter VAR phase - missing for high PF?

Post by Jameson »

Thanks jcb,

Yes, I think I see what you are saying. Now if the meter reports 1.00 Power Factor, and 2 VARs on Line 1, you cannot tell if these 2 VARS are inductive or capacitive, you have to make a best guess at this point. Is this true?

But if the power factor is 0.99 then you will know if the VARs are inductive or capacitive. Correct?

What you want is for the meter to report 1.00 Power Factor and indicate C or L in the RS485 data so that you know if the VARs (though there are not a lot) are inductive or capacitive.

Until now we have considered 1.00 Power Factor to be unity power factor and have not considered the need to know if it is edging towards inductive or capacitive. You are saying that if you had this piece of information that it would help you to determine better what is going on in your systems.

I will add this to the hopper of firmware changes to future meter models. At this point I am not sure that this data is available to us directly from our metering chip. We will look into it. Also I dont know right off how this will affect the EKM Push or EKM Dash (there are a few things to consider) If there is anyone else out there that has the same need, please chime in so that we can know it is also an issue for others.

Thanks again jcb, please keep the ideas coming!
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371
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