High impedance low amperage ground fault on the PV system's AC side?

[PradeepBalu]

What would happen if there was a high impedance low amperage ground fault on the PV system's AC side?
Our specifications call out ground fault protection required in our main solar disconnect. (a small relay that would trip if the high impedance, low amperage condition is met).

If there is no GFPE protection. What would be the consequences of a ground fault? Could inverters be damaged? Could fuses in the main disconnect blow? If you have any insight, please share - thanks!

 

[ron]

If there is no GFP, then the fault continues until the phase current protection trips, or fire makes everyone run away

 

[jaggedben]

Essentially the theory is no different for a PV system than any other AC feeder. However, given the right circumstances, the PV system could supply the current to the fault, meaning that the fault could actually have relatively high amperage and still not trip the main breaker without GFP.

You should also look at 705.32 and make sure your GFP device is appropriate for the application.

 

[ron]

I suspect GFP is important for PV since the inverter is not capable of providing large amounts of fault current

 

[jaggedben]

I suspect GFP is important for PV since the inverter is not capable of providing large amounts of fault current

GFP (or GFDI, as it's called in 690) is critical on the DC side of PV systems. On the AC side of grid tied systems things are usually still dominated by the utility for small to medium systems and no additional GFP is needed. A short or other GF problem on the AC side may cause enough of a voltage disturbance to trip the PV inverter off line at least for a few minutes. I have never had to deal with AC GFP for the residential and small commercial systems I've worked on. However, presumably if our OPs system needs GFP then it is large enough that arguably an engineer should be looking at the fault current contribution. (Or else, if it's actually a smaller system, perhaps the GFP isn't really necessary and was called for by mistake.)