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
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/
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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