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Franklin France presents you the Saint-Elme lightning conductor. It results from the research work conducted with the French Atomic Energy Commission, and is the efficient, inexpensive and clean protection solution, using piezo – electric ceramics to transform the wind energy into electric energy.
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Principle ; A rod – type lightning conductor, connected to earth, efficiently works by altering, at its level, the equipotentials which match the structures of the building it protects. The emergence of the lightning rod is an important factor in increasing the local electric field. The principle of the piezoelectric lightning conductor designed by Franklin France relies on several factors : the reinforcement of the local electric field and the early creation of a preferential discharge channel.
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Description; The SAINT-ELME® piezoelectric lightning conductor is mainly composed of the following :
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• Capture head ; Profiled, inalterable and good conductor, structured to generate a forced air circulation at its tip and in its prolongation (VENTURI system : air intakes and peripheral ejectors).
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Support pole ; Of treated copper (or stainless steel according to models) which upper part has one or more stainless steel ion emitter points, inserted in an insulating sleeve and subjected to the potential supplied by the piezo–electric ceramic. The emitter points are protected from direct impact by lightning and from the weather by the capture head which, like the support pole, is permanently connected to the earth potential.
Transducer (piezoelectric stimulator) ; Built into the lower part of the pole and consisting of piezoelectric ceramics stressed in an insulating container, combined with a simple, perfectly reliable and mechanical stimulation system (CEA and FRANKLIN patents). A high – voltage cable running inside the pole connects the stimulator to the emitter point(s). The voltage created by the ceramic is applied to the emitter point through the high voltage cable
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 Piezoelectric Stimulation ; The basic principle of the Saint-Elme lightning conductor is to increase the number of free charges (ionized particles and electrons) in the air surrounding the lightning rod and to create, within a cloud–ground electric field, a channel of high relative conductivity constituting a preferential path for lightning.
Free charges are created by the corona effect by applying on the Saint-Elme lightning conductor’s ionized point(s) the voltage supplied by cells of piezo–electric ceramics (lead zirco–titanate); their feature is to produce a very high voltage by simply modifying the applied pressure. The Saint-Elme lightning conductor is therefore equipped with a mechanical device that transforms the stress resulting from the wind action on the lightning conductor into a pressure stress on the piezo–electric cells.The voltage therefore produced is applied, through the high voltage cable that runs inside the lightning conductor’s support pole, onto the ionized point(s) to create, by corona effect, free charges. Then, these charges are expulsed, by the venturi system, from the lightning conductor’s head, profiled on purpose (forced air circulation). When they are outside the head, these charges are submitted to the cloud–ground electrical field. The charges polarized like the cloud are repelled towards the ground, the channel of charges that forms in prolongation of the lightning conductor is then exclusively composed of charges from the opposite pole to the cloud’s electric pole (it takes into account the discharges’s pole : positive or negative).
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The zones of protection of lightning conductors are obtained theoratically by plotting the electrogeometric model, but are comparable in practice, for low heights, to a cone of revolution which apex is the tip of the lightning conductor.
French standard NFC 17 100 describes the calculation method applicable to Franklin and meshed cages rods.
French standard NFC 17 102 deals with early streamer emission (ESE) lightning conductors, and takes into account the levels of protection Np of varying severity (I to III), to be determined previously by an assessment of the lightning risk for each project.
It defines the installation rules and the radii of protection Rp (m) depending on the average excitation advanceΔ L (m) of the lightning conductors and the excitation distance D (m), considered according to the degree of severity : D (I) = 20 m, D (II) = 45 m, D (III) = 60 m.
The table hereunder gives the Rp (m) values for the three levels of protection Np depending on the actual height h(m) of the Saint-Elme lightning conductor in relation to the different planes considered.
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Lightning Risk Assessment
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The Equivalent Collection Area of Structure
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Ae= L.W+6.H.(L+W)+9.P.H2
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L= Lenght (M)
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W= Width (M)
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H= Height (M)
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Expended Lightning Frequency
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Nd= Ng.Ae.C1.10-6
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(Ng) = 0.04• Nk 1.25
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Accepted Lightning Frequency
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Nk ; Annual Average Thunder Days Number
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Accepted Lightning Frequency
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C=C2.C3.C4.C5
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Nc=5,5.10-3/C
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C1=1 C2=0.5 C3=1 C4=1 C5=5 C=2.5
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Nd ≤ Nc Optional Protection
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Nd > Nc Protection Required
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Efficiency
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E>0.98 Level 1 + Add
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0.95<E<0.98 Level 1
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0.90<E<0.95 Level 2
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0.80<E<0.90 Level 3
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E<0 Level 4
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Product details in PDF format
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Lightning Rods Strike Risk Assessment Programme
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