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18kpv CT Power Offset

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Justdr5

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May 20, 2021
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The values for grid consumption are way off reality in my system. I see L1=3.69A and L2=5.01A which should translate to around 1k W. I do see a variable labelled as CT power offset but I did not find anything in the manual on this. I am guessing I need to change this value to offset the currently displayed value to the correct ones but wanted to check in with this group before doing so. Thanks.




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nuke said:
one of them my be reversed? the CT offset is in the "0-100 watts" range
Click to expand...
Just double checked, they seem to be in the right direction. Also, from the maintenance dashboard it shows the range is -1000,1000. But maybe it is -100,100?

20240126_084440.jpg2024-01-26 08_45_12-Remote Set - Monitor Center.png
 
Can you unclamp one of the CTs from the inputs, then evaluate what your meter says vs the 18kpv for the remaining input?

Then re-attach the other CT, detach the first one, and do the same?

This gives us some more troubleshooting data that might explain the problem. Also - read your settings and tell us if the CT power offset is set to anything right now
 
Are you accounting for active power vs apparent power when comparing the two? Depends on how much the house is pulling/pushing.

If you just take current measurements and no accounting for voltage/shift between current and voltage you are doing apparent power
 
nuke said:
Can you unclamp one of the CTs from the inputs, then evaluate what your meter says vs the 18kpv for the remaining input?

Then re-attach the other CT, detach the first one, and do the same?

This gives us some more troubleshooting data that might explain the problem. Also - read your settings and tell us if the CT power offset is set to anything right now
Click to expand...
Will do. Can't actually measure it now as the sun is up=)
 
zanydroid said:
Are you accounting for active power vs apparent power when comparing the two? Depends on how much the house is pulling/pushing.

If you just take current measurements and no accounting for voltage/shift between current and voltage you are doing apparent power
Click to expand...
yes I believe the current clamp does not know voltage so it would be considered "apparent current" if there was such a thing. That being said, taking the current read and multiplying by voltage should get me in the neighborhood right? I am seeing 250W on the inverter screen but I am drawing ~1k ish in reality. I also confirmed with my transfer switch / sense device and they are all around ~1k watt draw. I spoke with Signature and they changed my CT power offset value to -40. I will not know if this had a positive impact until the sun goes down (and the battery runs low). Thanks for your response.
 
Justdr5 said:
yes I believe the current clamp does not know voltage so it would be considered "apparent current" if there was such a thing.
Click to expand...

It's just RMS current, it's real. The question is how much power is going through them

Justdr5 said:
That being said, taking the current read and multiplying by voltage should get me in the neighborhood right?
Click to expand...

Depends on what the loads are. If all the load is from barely corrected or uncorrected power supplies (like bunch of DC wall warts) then you can easily be off by 30-40%. Same if it's a bunch of motor loads (both AC motors and inverter-driven/ECM motors with a power conversion stage in front)

Justdr5 said:
I am seeing 250W on the inverter screen but I am drawing ~1k ish in reality. I also confirmed with my transfer switch / sense device and they are all around ~1k watt draw. I spoke with Signature and they changed my CT power offset value to -40. I will not know if this had a positive impact until the sun goes down (and the battery runs low). Thanks for your response.
Click to expand...

OK if you have other things measuring 1kW power (kW is always active by definition) then there is something wrong.
 
Justdr5 said:
Firmware up-to-date. 6 gauge wire isn't sufficient for 50A?
Click to expand...
#6 is fine, I think it just looks like a clown shoe situation sitting inside a CT intended for 200A

Justdr5 said:
Yeah this confused me as well. Going to hunt around as the offset metric info wasn't included in the manual. Thanks.
Click to expand...
If they had documentation or tooltip explaining what that setting mathematically does, life would be easier. Maybe ping one of the EG4 folks.

There is also the possibility that one or both of the CTs is just busted, some of the suggestions upthread on connecting only one or the other would help narrow that down.
 
So tonight I had a heater running plus my normal ~1k draw for a total of ~5k. The 18kpv shows 1600W. I also pulled each CT off 1 at a time and the power draw changed to ~800W total when taking off the L1 CT and ~800W when taking off the L2 CT. The CT Power offset seemed to have no affect on this value as I tried switching it to 0 and back to the -40 that SS suggested.

2024-01-26 21_31_44-Sense.png20240126_213247.jpg20240126_213346.jpg20240126_213226.jpg
 
Is there a setting for turns ratio? Is the ratio on the CTs correct?

You can also do something dumb and make 3 turns within each one with your #6. The CTs can handle 200A so maybe it’s safe.
 
Under Advanced, is your CT set to 1/3000
 

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BKY2003 said:
Under Advanced, is your CT set to 1/3000
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LOL, great that they provide this setting.

But why would they ship the firmware/CT with the wrong default... and not have this be part of the customer support script.

The % of customers buying these that know beyond cave man installation of magic electrical components is pretty low.
 
does your L1 at the 18Kpv match the meters L1?
 

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BKY2003 said:
I can’t take credit, Nuke caught it. Did it fix it.
Click to expand...
It seems much closer now. Off by 10% or so instead of 80%=) Credit points distributed as follows: Nuke=2, Zanydroid=2, BKY2003=1, Quattro=1. Appreciate your help all.
 
Justdr5 said:
So tonight I had a heater running plus my normal ~1k draw for a total of ~5k. The 18kpv shows 1600W. I also pulled each CT off 1 at a time and the power draw changed to ~800W total when taking off the L1 CT and ~800W when taking off the L2 CT. The CT Power offset seemed to have no affect on this value as I tried switching it to 0 and back to the -40 that SS suggested.

View attachment 191566View attachment 191568View attachment 191569View attachment 191570
Click to expand...
Hello ， Do you have a digital energy meter to measure both the active power and apparent power ?
When there is grid power , the inverter just show the active power part of the grid import /export since the inverter will synchronize to the grid voltage , so if there is reactive power part , the inverter won't display it , you could see when the inverter works in power backup mode , there are Peps and Seps , both the active and reactive part are showing .
But the Amp meter could measure the RMS value without considering the power factor between grid voltage and current .If there is digital energy meter, you should be able to read the active power(P) and apparent power(S) directly .
But if it is the CT ratio issue , you could be able to find it easily , you could check if the CT ratio configuration via inverter is same as the real CT ratio .
 
Joe Chan said:
Hello ， Do you have a digital energy meter to measure both the active power and apparent power ?
When there is grid power , the inverter just show the active power part of the grid import /export since the inverter will synchronize to the grid voltage , so if there is reactive power part , the inverter won't display it , you could see when the inverter works in power backup mode , there are Peps and Seps , both the active and reactive part are showing .
But the Amp meter could measure the RMS value without considering the power factor between grid voltage and current .If there is digital energy meter, you should be able to read the active power(P) and apparent power(S) directly .
But if it is the CT ratio issue , you could be able to find it easily , you could check if the CT ratio configuration via inverter is same as the real CT ratio .
Click to expand...

I think the power factor issue has been ruled out, there is another energy meter (reading active power, not shown in this picture, I think it's a Sense so it should be accurate) that shows higher draw compared to what the 18kpv is showing. And it is similar to the numbers that amp meter suggests.
 
Joe Chan said:
Hello ， Do you have a digital energy meter to measure both the active power and apparent power ?
When there is grid power , the inverter just show the active power part of the grid import /export since the inverter will synchronize to the grid voltage , so if there is reactive power part , the inverter won't display it , you could see when the inverter works in power backup mode , there are Peps and Seps , both the active and reactive part are showing .
But the Amp meter could measure the RMS value without considering the power factor between grid voltage and current .If there is digital energy meter, you should be able to read the active power(P) and apparent power(S) directly .
But if it is the CT ratio issue , you could be able to find it easily , you could check if the CT ratio configuration via inverter is same as the real CT ratio .
Click to expand...
Yes the problem was that I was showing values which where waaaaay off. Most of my loads are resistive so to see such a huge difference between measured and displayed was confusing. Looks like the default for my CT ratio wasn't correct. I do not know anything about CT's but I assume it has some number of wire loops(turns?) within and that current is measured via magnetic field (100% guessing on this). I assume the ratio has something to do with the number of loops. Mine appears to have been the incorrect setting.
 
Justdr5 said:
Yes the problem was that I was showing values which were waaaaay off. Most of my loads are resistive so to see such a huge difference between measured and displayed was confusing. Looks like the default for my CT ratio wasn't correct. I do not know anything about CT's but I assume it has some number of wire loops(turns?) within and that current is measured via magnetic field (100% guessing on this). I assume the ratio has something to do with the number of loops. Mine appears to have been the incorrect setting.
Click to expand...
CT is a transformer (Current Transformer) that will scale the current in the monitored conductor to a lower current (or a voltage in some versions).

The turns ratio is covered in Wikipedia article:

en.wikipedia.org

Current transformer - Wikipedia

en.wikipedia.org en.wikipedia.org
 
So I don't know if my question/problem is related or not...any time I'm using batteries or PV only, nothing coming from grid(at least not supposed to be) I'm seeing around 4amps flowing on both L1 and L2 with clamp on meter. The inverter display shows zero...
Where's that 1000watts going???
CT offset -40
Ratio 1/3000

If I switch over to grid use, the display and my amp meter match pretty well. Meter also agrees with what 18kpv is showing going to loads.
If I disconnect grid the flow shows 0 with clamp on meter so i know the meter is working
 
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