jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
This is more of a theory question....
We have a system with a Power-One transformerless inverter that is frequently throwing a ground fault error on startup in the morning, apparently moisture related. If it doesn't give the error on startup, it doesn't throw it during operation either.
My understanding is that these inverters perform something similar to a Megger test on the conductors prior to startup. (They also monitor for current imbalance between + and - during operation.)
My question concerns how the solar panels affect the pre-start test. Would this test work through the solar cells? If there's a fault on the wiring somewhere between two of the solar modules, would the the test be significantly less likely to catch it? Conversely, is it reasonable to assume that the fault is most likely on the 'home-run' conductors and not between the panels?
IIRC, the inverter was indicating 0.1 Megaohm resistance between some conductor and ground in the prestart test, and this is too little. (3ma at the open circuit voltage, but that's considered dangerous. Arrgh.) I'm curious about your thoughts on how the resistance of the cells compares and how it would affect the test. I don't really understand what the cells would do when a different source attempts to push a voltage through them.
We have a system with a Power-One transformerless inverter that is frequently throwing a ground fault error on startup in the morning, apparently moisture related. If it doesn't give the error on startup, it doesn't throw it during operation either.
My understanding is that these inverters perform something similar to a Megger test on the conductors prior to startup. (They also monitor for current imbalance between + and - during operation.)
My question concerns how the solar panels affect the pre-start test. Would this test work through the solar cells? If there's a fault on the wiring somewhere between two of the solar modules, would the the test be significantly less likely to catch it? Conversely, is it reasonable to assume that the fault is most likely on the 'home-run' conductors and not between the panels?
IIRC, the inverter was indicating 0.1 Megaohm resistance between some conductor and ground in the prestart test, and this is too little. (3ma at the open circuit voltage, but that's considered dangerous. Arrgh.) I'm curious about your thoughts on how the resistance of the cells compares and how it would affect the test. I don't really understand what the cells would do when a different source attempts to push a voltage through them.