I bought a VM-3P75CT to experiment with as a grid meter for my home and am trying to understand its personality.
My system is very simple: RPi running v3.70-5, VM-3P75CT on v1.08 connected on Ethernet. House is single phase with an older SMA PV not talking to the GX device. (There is an MPPT charging a 12V LFP battery but that’s irrelevant).
I’m confused about erratic Neutral Current values.
Sometimes it reads about 10% of the L1 current (above image) and sometimes it roughly matches the L1 current (below image). A bug?
My question: How is the Neutral Current derived (as it’s not a measured value with a CT, so must be a calculated value)? And is there any purpose in including it? (Maybe in a 3-phase system?).
Secondary curiosity question: What is the PE Voltage referenced to? And what is its intended purpose? Identify a faulty Neutral-Earth bond perhaps?
Thanks in advance for filling in gaps in my understanding.
Cheers
Phil