Solar Hybrid Inverter extreme Power Factor

[hgg]

Hi,

I am using a new 3kW hybrid inverter made by Phocos and I've noticed something unusual.
I have installed in the house the OWL power meter that connects to the main grid entry point with current clamps.
When the battery gets depleted during late afternoon, the inverter switches immediately to grid power.
Then when the loads (400W) connected to the inverter are switched off, the power meter is showing 200W more than
usual.  If I measure the power consumption of the inverter directly on the socket which is connected with a socket
mains power meter, it shows around 10 watts, not 200 watts.  But it also shows a power factor of 0.05!
When the loads are switched back on the power factor goes up to 0.6

Is this normal? 
What is the impact of the extra 200 watts shown on the Owl power meter?
0.05 power factor?

Thanks.

[bdunham7]

Your OWL power meter is measuring VA (even if it doesn't display that way) and your other meter is measuring watts correctly.  I'll assume the OWL doesn't show you the power factor.

200VA x 0.05PF => 10W.  This is due to the inverter representing a capacitive load when it is dormant, this is fairly common and not a problem.  In other words there is about 0.85A of reactive current in the circuit with small losses that add up to 10 watts dissipated.

[hgg]

Thanks.  Yes, the Owl power meter does not show power factor.
So, I shouldn't freak out when the Owl shows 200 Watts more?...  :-)
I've heard that with some companies you pay a fine for low power factor.

So, I have to find a power meter similar to the Owl that displays true power correctly.
By the way, do you know if there is a way to correct that low power factor
the inverter is presenting to the grid?

[bdunham7]

I've heard that with some companies you pay a fine for low power factor.

By the way, do you know if there is a way to correct that low power factor
the inverter is presenting to the grid?

I doubt the power company is going to worry about such a small issue, especially since most low power factors result from lagging current (inductive loads) or harmonic distortion (non-PFC SMPS), not leading current from capacitors.  In fact, power companies use banks of capacitors and other things to compensate for lagging currents, so you're helping a bit. 

Don't worry about correcting it, as soon as you turn on any of your other loads you probably swing it back the other way and the inverter's capacitor is actually increasing the PF.

[hgg]

Just found the following on the OWL website helpdesk:


"Phantom Power" removal - Overnight generation
OWL Help Centre Agent 3
12 January 2022 06:07

"Phantom Power" is a "feature" of all PV Inverters. This is where it appears to an electricity monitoring device that the solar power is being generated even when it is dark!
 
This Phantom Power is actually reactive power and does not register on the electricity meter. Unfortunately current clamp sensor technology that we (and others) use does not allow us to differentiate between reactive and real power, and hence the Phantom Power is detected in the same way as the true generated power is.


So, this power meter cannot measure real power.
The strange thing is that my previous inverter, the MPPSolar 2.4kW hybrid, did not register any phantom power
with or without any loads while working on-grid.  How is this possible?

[barshatriplee]

 Power factor of 0.05 is very low. Maybe there was a problem at the time of installation or calibration. 

[hgg]

It cannot be calibrated.  What kind of problem do you mean?

[bdunham7]

So, this power meter cannot measure real power.
The strange thing is that my previous inverter, the MPPSolar 2.4kW hybrid, did not register any phantom power
with or without any loads while working on-grid.  How is this possible?

Apparently it isn't measuring power at all, just current. 

Your previous unit may have had a relay to disconnect it entirely when it was dormant or it may have had a much smaller output capacitance.

[Marco]

Why don't they just add a mains plug to the OWL? Read the phase and amplitude from the plug and the current from the clamp.

[hgg]

Apparently it isn't measuring power at all, just current. 

Your previous unit may have had a relay to disconnect it entirely when it was dormant or it may have had a much smaller output capacitance.

And the new one costs 3 times more...

[hgg]

Why don't they just add a mains plug to the OWL? Read the phase and amplitude from the plug and the current from the clamp.

Indeed. 

The thing is, that the Owl is measuring the actual current that is flowing in the wire.
How is this phantom power, since there is actual current in the wire?
Where does this current gets dissipated?  Which device consumes it?

[Marco]

Some capacitors are storing and returning it.

[hgg]

So, is it energy that is going back and forth at each cycle between the inverter and the
electricity supplier?
If that is so, then it will slowly be converted into heat by the resistance of the cables and
at the end someone has to pay for that...

[bdunham7]

If that is so, then it will slowly be converted into heat by the resistance of the cables and
at the end someone has to pay for that...

True, and the current multiplied by the voltage drop in the cable give you the real component of the power.  To the extent that power is dissipated in your house after the meter, you pay for it.  The cost of the part that is dissipated by the utility equipment before the meter is typically not recovered by the utility unless your service is large enough that they assess you additional fees based on power factor.

[alligatorblues]

I think the smart utility meters take power factor  into consideration, and add it to the power used. I've learned an important lesson: there are excellent ways to save money on electricity, but solar-electric power isn't one of them. California has a 1 megawatt solar cell generator that cost a billion dollars.  You can build a 15MW nuclear plant for that.

[hgg]

Luckily we do not have yet smart meters but they are on the way..
I think I will wire a timer relay to switch off the grid AC input to the inverter during the night.

[johansen]

The smart meters that have a rotating disk have a 2 pole flag on the disk and a quadrature encoder to count the turns.

As for 200va and 10 watts.. thats a 10uf capacitor. Or two 4.7 watt capacitors plus 10 watts of losses.

Residential meters dont count kva, only kwh. And of one "large general service" that i know of in washington.. thr kva demand charge is like 100$ a month on a plant with a 40kusd a month bill. I worked the numbers out, the utility is charging the customer approximately.. exactly, the expected lifecycle costs of capacitors to offset the load.

That may not be the case in california.

[hgg]

"As for 200va and 10 watts.. thats a 10uf capacitor. "

How do you calculate that?

[johansen]

"As for 200va and 10 watts.. thats a 10uf capacitor. "

How do you calculate that?

1 over 2 pi frequency farads is capacitive reactance

2 times pi times 60hz is 377. Reciprocal of that is .00265

As such a 10uf cap pulls 1 amp at 265vac at 60hz. 

[Marco]

California has a 1 megawatt solar cell generator that cost a billion dollars.  You can build a 15MW nuclear plant for that.

You can also build 600 MW peak utility scale PV for that.

[240RS]

So, is it energy that is going back and forth at each cycle between the inverter and the
electricity supplier?
If that is so, then it will slowly be converted into heat by the resistance of the cables and
at the end someone has to pay for that...

Depends. If there is 200var inductive reactive power (Q) in your house, the energy will not travel back and forth the the supplier at all. It will cycle in your home. If you do not have inductive reactie Q yourself, somebody in your street will. And it then cancels out.

I would say, no worries, it is just a line filter.

[hgg]

One think I do not understand is that when I switch on the loads (PC, TV & stereo amp) for a total of around 400 watts, then the power factor measured directly at the inverter grid input climbs to 0.6
With no loads it drops down to 0.05

[Siwastaja]

As others have said, that OWL thing is not a power meter. It's meaningless. Ignore it.

[hgg]

The power factor was measured directly at the inverter AC input.
Nothing to do with the OWL meter.

[Siwastaja]

Poor power factor at low loads is completely normal. Power factor itself is not meaningful. Showing real and reactive power in Watts directly would be more intuitive, than their ratio. Imagine a situation with 0.00000000000000000000000000001W of reactive power. Is it a problem? Yet if real power is 0.0000000000000000000000000000001W, calculated power factor is just 0.01, giving an impression of something being wrong.