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: [email protected] ; 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 <[email protected]> wrote: From: Drake Chamberlin <[email protected]> Subject: Re: [RE-wrenches] Lightning protection system To: "RE-wrenches" <[email protected]> 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 _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org Drake Chamberlin Athens Electric OH License 44810 CO License 3773 740-448-7328 740-856-9648 _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ---------------------------------------------------------------------------- No virus found in this incoming message. 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