Module grounding revisited [RE-wrenches]

[Joel Davidson]

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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