[RE-wrenches] Lightning protection system

Darryl Thayer daryl_solar at yahoo.com
Tue Mar 10 21:04:04 PDT 2009 

If the lightning pulse is 10,000 amps and I want to limit it to 1000 volts I need less than 1/10 ohm.  I guess that 1 ohm would be ok?  yes even here in minnesota often strikes come before rain.  

I have used two types of meter, Fall of potential and clamp type. Fall of potential meters use two ground rods one at 100 feet away and one at 40? feet away, and your ground rod.  They can measure to .01 ohm.  the other type requires two ground rods, or a well or water pipe and a ground rod. you clamp the meter like an amprobe around the wire and it induces a current and measures the amount of current induced.  


--- On Tue, 3/10/09, Joel Davidson <joel.davidson at sbcglobal.net> wrote:

> From: Joel Davidson <joel.davidson at sbcglobal.net>
> Subject: Re: [RE-wrenches] Lightning protection system
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Tuesday, March 10, 2009, 10:16 PM
> A few years ago, Bill Brooks or another wrench specified 5
> ohms or less when 
> measured with a special meter but I can't recall the
> meter. No problem if 
> the ground is saturated, but lightning in the southwest US
> often comes in 
> the storm front before the soaking rain.
> 
> ----- Original Message ----- 
> From: "Darryl Thayer"
> <daryl_solar at yahoo.com>
> To: "RE-wrenches"
> <re-wrenches at lists.re-wrenches.org>
> Sent: Tuesday, March 10, 2009 6:51 PM
> Subject: Re: [RE-wrenches] Lightning protection system
> 
> 
> >
> > Thanks Joel
> > the Lightning and Transients research Institute has
> been closed, I am 
> > sorry to say.  The paper is valuable and reassuring,
> if the module frames 
> > are properly grounded, they act as a shield and will
> protect the PV source 
> > and output circuits if they are shielded via conduit
> or coaxial cable. 
> > This also implies the grounding system should be of
> low resistance.
> > DAryl
> >
> >
> > --- On Tue, 3/10/09, Joel Davidson
> <joel.davidson at sbcglobal.net> wrote:
> >
> >> From: Joel Davidson
> <joel.davidson at sbcglobal.net>
> >> Subject: Re: [RE-wrenches] Lightning protection
> system
> >> To: "RE-wrenches"
> <re-wrenches at lists.re-wrenches.org>
> >> Date: Tuesday, March 10, 2009, 8:14 PM
> >> 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.
> >>
> >> Joel Davidson
> >>
> >>   ----- Original Message ----- 
> >>   From: Matt Tritt
> >>   To: daryl_solar at yahoo.com ; RE-wrenches
> >>   Cc: trang donovan
> >>   Sent: Monday, March 09, 2009 11:04 AM
> >>   Subject: Re: [RE-wrenches] Lightning protection
> system
> >>
> >>
> >>   Hi Darryl,
> >>
> >>   Just to see what your take would be, and
> other's -
> >> what would the case be should the modules have
> >> non-conducting frames (or even no frames)is the
> case with
> >> some systems on the market?
> >>
> >>   Matt T
> >>
> >>   Darryl Thayer wrote:
> >> Yes the electric power and atmospheric grounding
> systems
> >> should be connected together to serve as a larger
> better
> >> grounding system.  The Electrical code requires
> that at only
> >> one point does the neutral (grounded) conductor of
> the
> >> electrical power system get connected to the
> grounding
> >> system, this is to prevent the grounding electrode
> system
> >> from carrying electrical power system currents. 
> The
> >> electrical power system is to be grounded to
> prevent the
> >> electrical power system from differentiating its
> self via
> >> the injection of energy from other electric power
> sources
> >> including atmospheric electrical energy.
> >>
> >>
> >> The lightening protection system is to create a
> path from
> >> the atmospheric energy to the earth grounding
> system.
> >> ((Wind rain, dust and friction cause the
> atmosphere to
> >> become charged relative to the earth, conducting
> objects can
> >> build a charge if not electrically connected to
> the earth,
> >> these current flow all the time, although they are
> small
> >> sometimes, and in the case of a lightening strike
> incredibly
> >> large.  Even small currents can build large
> voltages and
> >> fail electronic components.
> >>
> >> The frames of solar modules are electrical
> conduction
> >> components not normally charged that can present a
> personal,
> >> and physical damage potential (life-property) if
> they become
> >> charged by the electrical power system and
> therefor the
> >> underwriters require they be protected by
> grounding.  This
> >> accidental energy need to be safely returned to
> the
> >> electrical power system, and properly this is
> called bonding
> >> back to the neutral conductor.  This grounding is
> described
> >> by the NEC in 690 and 250 primarily.   The frames
> of the
> >> modules can become charged by atmospheric energy
> energy,
> >> this energy needs to be returned to the earth, via
> the
> >> lightening protection system, ie grounding
> electrode system.
> >>  The code says little about this, however, it is
> addressed
> >> in 690 and 250.
> >>
> >> Sorry I said so much.
> >> Darryl
> >>
> >>
> >> --- On Fri, 3/6/09, Drake Chamberlin
> >> <drake.chamberlin at redwoodalliance.org>
> wrote:
> >>
> >>   From: Drake Chamberlin
> >> <drake.chamberlin at redwoodalliance.org>
> >> Subject: Re: [RE-wrenches] Lightning protection
> system
> >> To: "RE-wrenches"
> >> <re-wrenches at lists.re-wrenches.org>
> >> Date: Friday, March 6, 2009, 8:47 AM
> >> I didn't get a reply to the question about
> connecting
> >> the GEC to the
> >> lightning protection system on the 8 story
> building.
> >> Although this
> >> may seem like an intrinsically dangerous idea, a
> lightning
> >> protection
> >> system is required to be bonded to the building
> grounding
> >> electrode system.
> >>
> >> "250.106 Lightning Protection Systems.
> >> The lightning protection system ground terminals
> shall be
> >> bonded to
> >> the building or structure grounding electrode
> system."
> >>
> >> It would therefore seem that the suplemental
> ground could
> >> connect to
> >> that system as well, and in fact use the existing
> >> conductor.  Any
> >> input would be welcome.
> >>
> >> Thanks,
> >>
> >> Drake
> >>
> >>
> >>
> >>
> >> At 09:19 PM 3/4/2009, you wrote:
> >>     Hello Wrenches,
> >>
> >> Can the supplemental grounding electrode conductor
> be
> >>       connected to a
> >>     lightning protection system?
> >>
> >> We have a case where it would be difficult to run
> a GEC
> >>       down a multi
> >>     story building, but have a convenient copper
> wire, from
> >>       a lightning
> >>     protection system, that runs to a rod.
> >>
> >> Thank you,
> >>
> >> Drake Chamberlin
> >> Athens Electric
> >> OH License 44810
> >> CO License 3773
> >> 740-448-7328
> >> 740-856-9648
> >>
> >>
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> >>       Drake Chamberlin
> >> Athens Electric
> >> OH License 44810
> >> CO License 3773
> >> 740-448-7328
> >> 740-856-9648
> >>
> >>
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