[RE-wrenches] active vs apparent power readings with solar

[Kienan Maxfield]

I’m not sure if I fully get what’s was going on or where he was measuring… all of the readings are low (below 1 kW) if he was messing at the meter after the household load has combined with the PV output, then this could make sense. The household loads could be using some apparent power, but the inverters are only putting out real power, so the PV is offsetting all the real power but there’s still some apparent power left, so the overall power factor is ridiculously low.

On the other hand, if all the loads are turned off and he’s really only measuring the PV output, then something wrong and I’d think it’s more likely that the measurements are wrong because I don’t see any way that the PV could put out such a bad power factor.

Here’s a hypothetical of what I mean in the first paragraph… if load A had a PF of 0.8, and it’s consuming 3 kW, then it’s apparent power is 3.75 kVA. If the PV is producing 2.8 kW at a PF of 1, then it’s producing 2.8 kVA. The net reading would then be 0.2 kW real power and 0.95 kVA. That’s a PF of 0.21.
If the PV increases to 2.9 kW, then the real power is 0.1 and apparent power is 0.85 which is a power factor of 0.11

Hopefully this helps…

Thanks,
Kienan


Green-Go Solar Distribution LLC

Maxfield Solar LLC (installation and consulting company)

maxfieldsolar at hotmail.com<https://maxfieldsolar@hotmail.com/>

(801) 631-5584(Cell)

www.distribution.solar

On Apr 29, 2023, at 11:03 AM, Darryl Thayer via RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:


Hi all, if the micros are not producing power I would expect an extremely low power factor.  The power factor of all inverters is low not in use.  Make sure electrician is measuring during production.  My measurements are extra low for micro inverters.

On Thu, Apr 27, 2023, 4:11 PM August Goers via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Hi Wrenches,

We have a residential site with grid tied solar where there is an electrician involved who has gotten into taking site readings and thinks there is a power factor problem. My gut on it is that there is some sort of measurement reading error, and that the power factor should be around 1.

The electrician is using a Fluke 3540FC power monitor and has provided a spreadsheet comparing active power to apparent power and calculating power factor. See below (you might have to open the image and zoom in to read it). This measurement was taken with a PV system running, presumably sending some power back to the grid.  Note that the phase B active power measurement is negative (PV exporting to grid) and that the apparent power is positive. This nets in a power factor that is crazy low of 0.05.

Does anyone have experience about whether a meter like this can properly measure these readings - maybe there is a setting error or it can't deal with negative readings?

<image.png>


Best,

August
Luminalt
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