[RE-wrenches] Extensive Lightning Damage to Modules

[Kent Osterberg]

When a long circuit has surge protection at only one end, the voltage at 
the unprotected end of the wire will rise, by induction, during a 
lightning event that causes the surge protection to activate. There 
should be surge protection at both ends of long feeders to reduce 
possible damage from induced voltages.

Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
t: 541-568-4882


On 9/7/2012 11:14 AM, Jeff Irish wrote:
>
> Kent,
>
> Surge protection is at the inverters, 200 feet away, on both the AC 
> and DC sides.  Nothing at the array; never thought we'd need it 
> there.  There's a 4 string fused DC combiner on the west pole of each 
> row; no damage visible on any of them and their fuses were all ok.  
> And yes, each pole of 10 modules is a separate DC string, 4 are 
> combined into a DC output circuit to each of four SB7000US inverters.
>
> Jeff
>
> Hudson Solar
>
> *From:*re-wrenches-bounces at lists.re-wrenches.org 
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Kent 
> Osterberg
> *Sent:* Friday, September 07, 2012 11:56 AM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] Extensive Lightning Damage to Modules
>
> Jeff,
>
> Is there any surge protection in the combiner boxes? Any damage 
> visible in the combiner boxes? Any fuses or breakers open in the 
> combiner boxes? Is each pole a single string of modules or multiple 
> strings of modules?
>
> While there where undoubtedly ground currents flowing they probably 
> didn't cause the damage in the module junction boxes. The PV module 
> and wiring to it form a loop - often a loop with a large area in the 
> vicinity of the module. The current from the lightning strike has a 
> tremendous dI/dt and the changing magnetic field from it will induce 
> voltages in any wire loop.
>
> Kent Osterberg
> Blue Mountain Solar, Inc.
> www.bluemountainsolar.com  <http://www.bluemountainsolar.com>
> t: 541-568-4882
>   
>
> On 9/7/2012 7:40 AM, Jeff Irish wrote:
>
>     A customer of ours has recently suffered lightning damage to 31
>     out of 160 top of pole mounted modules.  This is the first time in
>     10 years that I've seen modules damaged by lightning.  Lots of
>     inverter GF fuses and a few inverters, but never modules.  We're
>     trying to determine if it was caused by the lightning flash
>     irradiating the modules or ground currents.
>
>     The array consists of 16 DP&W top of pole mounts with 10 modules
>     each, arranged in a square of 4 poles E-W and 4 rows N-S.  The
>     poles are 13 feet center to center E-W and the N-S row spacing is
>     about 50 feet.  The poles are 6 inch galvanized Technoposts,
>     augured 5 -- 7 feet into the firm ground, connected with a network
>     of about 160 feet of bare #6 copper and at least 8 copper plated
>     ground rods. Altogether we have about 130 square feet of bare
>     metal surface area connected and buried in the ground at and
>     around the array.
>
>     The customer saw lightning strike just after dawn a few weeks ago
>     a couple hundred feet to the southwest where it also destroyed two
>     utility pole mount distribution transformers and ran along the
>     utility wires 100 feet south of the array.  The inverters are 200
>     feet NW and suffered no damage.  The array and modules look
>     totally fine, except some of the J-boxes are deformed from heat. 
>     Opening the J-boxes shows varying levels of damage to one or more
>     diodes, from discoloration to being broken and cracked open.
>
>     The odd thing is the pattern of damage (we've tested all the
>     modules individually for Voc and Isc).  Only modules in the south
>     row of 4 poles are damaged, and the damage is concentrated on the
>     modules closest to the ground; modules higher up in the air appear
>     OK.  Also, damage is less frequent as you move east, away from the
>     direction of the strike.
>
>     If it was caused by ground currents, why would the current want to
>     go up the poles, why only the southern row of poles, and why
>     damage more modules closer to the ground and not those at the
>     top?  Is it possible a flash near the ground irradiated the
>     modules causing a current spike and the southern row shielded the
>     other rows from most of the flash?  Anyone have experience with this?
>
>     Jeff Irish, PE
>
>     President
>
>     Hudson Solar
>
>     13 Hook Road
>
>     Rhinebeck, NY 12572
>
>     T.845.876.3767x110
>
>     F.845.876.3912
>
>     jeff at hudsonsolar.com <mailto:jeff at hudsonsolar.com>
>
>     /Solar Electric Systems/
>
>     /NYSERDA Eligible PV Installer/
>
>     /NABCEP Certified Solar PV Installer/
>
>     /NABCEP Certified PV Technical Sales/
>
>     *MailScanner has detected a possible fraud attempt from
>     "applewebdata:" claiming to be* HudsonSolar.com
>     <applewebdata://B5F2562A-2B67-4161-84E4-42F12DC28720/www.hudsonsolar.com>
>
>     2011 NYSERDA Excellence in Quality Award | 2011 NYSEIA Award
>     Winner | 2009 Best of the Hudson Valley | 2008 SunPower Dealer of
>     the Year | EDC Business Excellence Award for Innovation
>
>
>

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