[RE-wrenches] Single Conductor Cable unprotected?

[Ray]

Greeting esteemed Wrenches;

I've recently come across some literature, install pics, and online 
information from manufacturers saying that its OK to run single 
conductor cables (THHW, RHH,etc) without conduit from the battery 
enclosure to the inverters, etc.  I'm pretty sure that's a cardinal No 
No, and violation of 300.3, but the NEC is actually not as clear as I 
was hoping. The general interpretation I've always seen: Its either 24" 
below grade (USE), in conduit below 8 ft, allowed in certain instances 
exposed over head (above 8 ft), or just for 690: allowed secured under 
the array if on a roof.

I've done "free flying cables" in the third world, and on RVs, but never 
on NEC compliant work.  Can someone reorient me to the proper 
interpretation?  or have I just been trying too hard all these years to 
put single conductor cables in conduit?

Thanks,

-- 
Ray Walters
Remote Solar
303 505-8760