Module grounding revisited [RE-wrenches]

Mon Nov 4 09:39:54 PST 2002

Joel,

So, did they also experiment with non-metallic frames? Did the aluminum act
as an attractant to lightning in this test, and thus become kind of a
self-fulfilling prophecy? What about modules with no frames at all? This is
what a composite framed module would, in effect, be.

Matt
----- Original Message -----
From: "Joel Davidson" <joeldavidson at earthlink.net>
To: <RE-wrenches at topica.com>
Sent: Monday, November 04, 2002 9:09 AM
Subject: Re: Module grounding revisited [RE-wrenches]

> In 1983 Arco Solar and the Lightning & Transients Research Institute,
> St. Paul, MN, presented a paper at the Greece PV conference titled
> "Ability of Photovoltaic Modules to Withstand Lightning Strikes."
>
> Summary: The ability of glass superstrate and metal/plastic substrate
> modules to withstand lightning strikes was examined. Each of 3 different
> types of modules were exposed to 4 nearby and 1 direct strike of high
> voltage long arc simulated lightning (400,000 volts, 10,000 amps), and
> to 1 direct strike of high current, long duration lightning (150,000 to
> 175,000 amps, 50,000 volts). Visual and electrical examination
> demonstrated that the high voltage strikes produced no electrical damage
> to the glass superstrate modules and little to the plastic substrate
> module. The high current, long duration strike resulted in varying
> degrees of physical damage to all modules but little or no loss in
> electrical performance.
>
> Conclusions: The experimental data indicate that a glass front module
> with a rigid metal frame is able to withstand almost any lightning
> strike if the frame is grounded to the earth. The metal frame acts as a
> grounding rod attracting all the current to it. However, a strike which
> breaches the integrity of the encapsulation might, under some
> conditions, eventually destroy the module. Data from the field appear to
> concur with the experimental data presented in this paper but also
> indicate that while the modules survive a lightning storm, additional
> protection may be required for the cabling, power conditioning
> equipment, and control systems. A grounding rod will protect the array
> from direct strikes but further protection is required for induced
> voltages and side flashes they can create. Shielding (e.g. coaxial
> cables) will protect the wiring. The terminals of the balance of system
> components can be protected by the use of nonlinear circuit elements
> known as terminal protection devices. These devices may be nonlinear
> resistors or varistors, semiconductor junction devices and dielectric
> breakdown devices or sparkgaps. The degree of protection needed for any
> particular installation will be determined by factors such as site
> location, size of the array, safety considerations and cost.
>
>
> matthew tritt wrote:
>
> > Max, et all,
> >
> > The logical way to build module frames is not with aluminum, but with a
> > non-metallic composite, such as carbon/fiberglass pultrusion. This is
vastly
> > stronger, lighter, more weather resistant and would not require any kind
of
> > grounding, as there would be no possibility of conductivity through the
> > frame. The mounting structure could also use composite mounting rails
for
> > the same reasons. Then this whole f----ing issue would be moot.
> >
> > Tell me why I'm wrong Steve and Bill, you champions of the dominant
> > paradigm!
> >
> > Matt
> > ----- Original Message -----
> > From: "Max Balchowsky" <max at seesolar.com>
> > To: <RE-wrenches at topica.com>
> > Sent: Sunday, November 03, 2002 7:04 PM
> > Subject: Re: Module grounding revisited [RE-wrenches]
> >
> > > Jerry, the AstroPower Manuel I have tells me to ground the Module
frames
> > to
> > > the Rails and the rail ground runs back to the main panel ground. It
also
> > > specifys that the grounding must be done so that if a panel is removed
> > from
> > > the string the others must remain grounded.(layin lug) It does say
that
> > the
> > > lug can be mounted so that the ground wire can be accessible after
module
> > is
> > > mounted against the roof.(drill into module frame?????). I've always
> > > wondered what module manufacturers were thinking (or were they) when
they
> > > put the ground screw hole near the middle of the module.......
> > >
> > > Max
> > >
> > > SEE Systems
> > > 100 S. Sunrise Wy
> > > Palm Springs, Ca. 92262
> > > 760-403-6810
> > >
> > > ----- Original Message -----
> > > From: "Jerry Caldwell" <solarcowboy at yahoo.com>
> > > To: <RE-wrenches at topica.com>
> > > Sent: Saturday, November 02, 2002 4:32 PM
> > > Subject: Re: Module grounding revisited [RE-wrenches]
> > >
> > >
> > > > We often ground the rack only.  Some of the ASE
> > > > modules we use have a thick coat of paint on the
> > > > frames, in which case we use the grounding disks
> > > > provided by ASE to ground the individual modules.
> > > >
> > > > Astropower includes Professional Solar Products
> > > > aluminum mounting rails in thier packaged kits and the
> > > > Astropower installation manual says that only
> > > > grounding the rails is necessary.  I'm not sure, but
> > > > they might even have gotten the assembly listed as
> > > > such.
> > > >
> > > > Jerry Caldwell
> > > > Light Energy Systems
> > > >
> > > > ,
> > > > > wrmiller at slonet.org writes:
> > > > >
> > > > >
> > > > > > Therefore, if one grounds a rack frame, the
> > > > > modules being "secured to and
> > > > > > in electrical contact with" the racks renders the
> > > > > module frames
> > > > > > "effectively grounded".
> > > > > >
> > > > > > Comments?
> > > > > >
> > > > >
> > > > > William,  My own on going test - experiment has been
> > > > > to rely on the frames
> > > > > getting grounded by the rack. I too think the
> > > > > individual ground wire strung
> > > > > panel to panel is stupid and a waste of time.
> > > > > Supporting this hypothesis is
> > > > > 100% ground continuity to every module frame and the
> > > > > main rack. I have tested
> > > > > every installation for ground over many years and
> > > > > never had an ungrounded
> > > > > frame. And I have gone back to old jobs and checked
> > > > > years later. Still good
> > > > > continuity.
> > > > >
> > > > > I think the language you found clearly gives the
> > > > > option to ground the rack.
> > > > >
> > > > > Don
> > > >
> > > >
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