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

[Drake]

We put lightning protection on an existing system at 9000' + in 
Colorado that had extensive lightning damage over the years. The key 
to solving the problem was grounding the system to the metal well 
casing, which went down over 200 feet.  We also added a some Delta 
lightning arrestors.  If they really aren't doing anything, it would 
be good to know.


At 07:02 PM 9/22/2011, you wrote:
>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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Drake Chamberlin
ATHENS ELECTRIC LLC
OH License 44810
CO license 3773
NABCEP Certified PV
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