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-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@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
j...@hudsonsolar.com <mailto:j...@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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