Hyundai PV Panel Array - RISO test help

[Graddie]

I have two 8 panel strings laid flat on a flat roof connected to a Power One inverter. One of the strings is showing a RISO of 0.5 mohm or less. The cables and connectors are all dry and intact, so I think is is a faulty panel. The voltage test doesn't identify the actual panel.

If I take off and disconnect each panel, what is the easiest way of testing each for leakage?

It is in a windy coastal salty environment.

Thanks for any help.

 

[SolarCity]

Are you totally sure that all of your connections are dry and intact? From what I've seen, these are far more likely to be the issue.

 

[BruceB]

I agree with SolarCity, but to answer your question you are looking for leakage to earth, so I would first test in situ:
- Unplug the dodgy string from the inverter.
- split the dodgy x8 string into two x4 strings then test between each string and earth.
- That will have narrowed it down to x4 panels.
- then split the dodgy x4 string into two x2 strings and test each string.
- That will have narrowed it down to two etc etc

As long as you have access it should not be difficult or time consuming

 

[Graddie]

Thanks to both above for replies. Very helpful. And surprise, surprise, we eventually found a broken connector, which was also very corroded! The next few days will confirm whether this has fixed the problem.

 

[BruceB]

On cue, I had an email from power one this morning saying they had published this:
Winter storms trigger low insulation resistance (RISO) issues | Power-One

 

[SolarCity]

Some really handy advice there, not just for Power One inverters. The test to determine the location of the fault should save a lot of time.

 

[Worcester]

Good article - just what we've been doing for three years, when we had one iso fault on a single string on an SMA tripower, not had a fault since (learnt our lessons )