[RE-wrenches] Designing PV systems for lightning prone areas

[Ray Walters]

Hi Jeff;

I'd look at using a lightning arrestor that is listed as a lightning 
protection device (UL 1449 rev. 3) The Deltas (which I've used for 
years) are just wires stuck in some sand. I have never had them actually 
work, but as you found, good grounding can do wonders. Take a look at 
the new Midnite solar arrestor, it has 8 MOVs. At least use a Citel, it 
will protect things till it cooks its single MOV.
Robin Gudgel did some testing and found that the Deltas don't even do 
anything till about 7000 volts.
Most electronics are HI pot tested to 2000 v, so the Deltas just aren't 
really stopping the damage.
He's planning a video at a 50,000 v test facility to see what the 
various protection devices can do.

You're ground grid sounds interesting, how many electrodes did you use?
Have you ever tried the really long electrodes, that you thread together 
in 10 ft sections, and can drive as deep as 80 ft? (I always wanted to 
try that system)
Did you tie to the rebar in the foundation or anything else interesting?
125 strikes a year is a lot, do you have a strike counter?

Always very interested in Lightning stories,

Ray Walters



On 9/22/2011 4:13 PM, Jeff Oldham wrote:
> Yep, lots of copper in the ground is key as is a suppression 
> specialist. I have a 23kW array on the top of a structure on the top 
> of a 400' remote island at 8 degrees from the Equator. This site 
> averages 125 strikes/year. We built a 4/0 CU ground grid completely 
> around and under the building and have a lightning rod at each corner 
> of the roof tied to this grid. Delta's everywhere and solid grounding. 
> In over 5 years we have "only" lost 2 CC's and one HUB10. I consider 
> this to be exceptional good considering the exposure. We are looking 
> at both Outback and Midnite solutions and 86 the Deltas.
> Good luck, 'cuz w/lightning luck counts for a lot!
> -jeff o
> From the Solar, Wind and Hydro powered office of Jeff 
> Oldham/Regenerative SOLutions
>
>
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