Monitoring DC current

[politics123]

Hey --

I'm installing solar PV, and apparently one of the challenges is determining if your panels are all performing correctly. There are warranties that cover replacement, but detecting a problem appears to be near impossible or very costly. I've found a few "power-plant grade" solutions, but these are $2000+.

Seems like a current transformer and a multimeter might be good. Do you need special CTs to measure DC current, or will any CR Magnetics CT work? How would one monitor (as in KWh used) DC current? I'd like something that outputs current in porportion to the DC power.

Solar Basics:
Panels are wired together in series (called "strings") and then multiple strings are wired in parallel to an inverter. So, say you have 20 panels using 4 strings of 5 panels each. I'd like to put a CT around each string and compare the power produced. If there are wide variations in the power per string, I might conclude I have a bad panel.

The inverters provide actual input (volts + watts) for the entire system, but that's not enough resolution to indicate one panel in one string having a problem!

 

[damage]

you could install microinverters instead of a central inverter. not really economical, but they are pretty cool tech. it's neat to see the time lapse production for some reference systems https://enlighten.enphaseenergy.com/systemslist

if you have an SMA/Sunny Boy inverter, there is some data you can extract through the use of an RS232 add in card. after a quick glance, it doesn't look like this will provide you what you need http://forums.sma-america.com/ubbthreads.p...amp;Number=2061

 

[KeepItSimpleStupid]

I'd like to first refer you to here: http://scienceshareware.com/how-to-measure...fect-clamp-.htm

It looks like they did a resonable job.

For one, Hall effect based transducers must be used to measure DC current. Voltage can be measured easily.
The problem is that each of the required signals are at different potentials and won't share the same reference, so some isolation is required.

I can probably answer what you don't understand.

 

[gatchel]

I aree with the micro inverter approach but isn't there a monthly fee to be able to get to the data logger information?