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prekursorius avatar image
prekursorius asked

Incorrect AC current smart meter readings

Hello,

we can't resolve a problem all the day. We have 3 phase system with Multiplus Cerbo and smart meter(first photo). The readings from the smart meter are incorrect; they differ by about twice compared to the readings from clamps on phase (3-phase clamps 4.1A and 2.3A in the app on second photo). We tried replacing the smart meter with another of the same model, but it didn't help. Both the phone and Cerbo show the same numbers, which are half of what the clamps indicate.

What could be wrong?


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7 Answers
ldoes (Victron Energy) avatar image
ldoes (Victron Energy) answered ·

Hi @Prekursorius, my first bet would be the configuration of your clamp multimeter. Can you set it to the lower range (60A) and make sure it is configured to measure AC (not AC/DC)?
Furthermore, it looks like there is quite a lot of distortion current (as indicated by low power factor) and your clamp multimeter might not play nicely with those nasty waveforms. Most meters that can handle this are marked as "True RMS" meters and yours doesn't seem to carry that label.

You can also hook all of the CTs over a single wire, and if all of them read the same current its a good indication that the VM-3P75CT is functioning normally.

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prekursorius avatar image prekursorius commented ·

Thank you for your answer.
As for the clamp settings, of course, I chose AC mode. And we're not talking about a difference in percentage; the discrepancy is in multiples. Check what the VRM shows (pay attention to the watts). The smart meter readings are clearly incorrect. I will try the test of hooking the CTs over a single wire.
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ldoes (Victron Energy) avatar image ldoes (Victron Energy) ♦♦ prekursorius commented ·

Hi @Prekursorius, the confusion between the power and current readings is due to a low power factor. See my answer to a related question here. This is either caused by non-resisitve loads in your system, or it might indicate that the CTs aren't hooked on the correct wires (L1 voltage port and L1 current port are measuring different phases).


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prekursorius avatar image
prekursorius answered ·


Connected correctly, we've checked it several times


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prekursorius avatar image
prekursorius answered ·

Colors are corect


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prekursorius avatar image
prekursorius answered ·

This is not the first time we have installed a Victron meter, we didn't have this problem before. the impression is that the CT rotation is wrong

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filbo avatar image
filbo answered ·

Hello everyone, I had similar problems and could not explain the values.
Phase L3 with over 2A should only supply a few watts? Makes no sense....

The solution was that the transformers (although the plastic clip was correctly closed) were not completely closed. After I additionally pressed them together with cable ties, it looks like the meter is delivering correct values.

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prekursorius avatar image
prekursorius answered ·

We haven't found the cause yet, so we just installed an Eastron meter, which shows the correct values. However, the Victron smart meter has not been uninstalled yet, so we will try Filbo's solution and I will post the results here.

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prekursorius answered ·

Filbo's solution didn't work for us, so the meter was uninstalled, and we used Eastron instead.

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