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Lightning rod

Diagram of a simple lightning rod system

A lightning rod (US, AUS) or lightning conductor(UK) is a metal rod or conductor mounted on top ofa building and electrically connected to the groundthrough a wire, to protect the building in the eventof lightning. If lightning strikes the building it willpreferentially strike the rod, and be conductedharmlessly to ground through the wire, instead ofpassing through the building, where it could start afire or cause electrocution. A lightning rod is asingle component in a lightning protection system.In addition to rods placed at regular intervals on thehighest portions of a structure, a lightningprotection system typically includes a rooftopnetwork of conductors, multiple conductive pathsfrom the roof to the ground, bonding connections tometallic objects within the structure and agrounding network. The rooftop lightning rod is ametal strip or rod, usually of copper or aluminum.Lightning protection systems are installed onstructures, trees, monuments, bridges or watervessels to protect from lightning damage. Individuallightning rods are sometimes called finials, airterminals or strike termination devices. Thelightning rod was invented by Benjamin Franklin inthe Americas in 1749[1] and, perhaps independently,by Prokop Diviš in Europe in 1754.[2]

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History

Nevyansk Tower crowned with ametallic rod grounded through a complex

system of rebars (some are seen at thebasement)

"Machina meteorologica" invented byDiviš worked like a lightning rod

As buildings became taller, lightning becomes more of a threat. Lightning candamage structures made of most materials (masonry, wood, concrete andsteel) as the huge currents involved can heat materials, causing a potential forfire, and also water to high temperatures.

Asia

Some of the most ancient lightning conductors can be found in Sri Lanka inplaces like the Anuradhapura Kingdom that dates back thousands of years.The Sinhalese kings, who mastered construction of stupas and advancedbuilding structures, installed a metal tip made of silver or copper on thehighest point of every building to conduct any lightning charge. In many partsof the world, ancient Buddhist monuments have been destroyed by lightningstrikes, but not in Sri Lanka.

Russia

A lightning conductor may have been intentionally used in the LeaningTower of Nevyansk. The spire of the tower is crowned with a metallic rod inthe shape of a gilded sphere with spikes. This lightning rod is groundedthrough the rebar carcass, which pierces the entire building.

The Nevyansk Tower was built between 1725 and 1732, on the orders ofindustrialist Akinfiy Demidov. The Nevyansk Tower was built 25 yearsbefore Benjamin Franklin's experiment and scientific explanation.[4]

However, the true intent behind the metal rooftop and rebars remainsunknown.[5]

Europe

The church tower of many European cities, usually the highest structure, wasthe building often hit by lightning. Early on, Christian churches tried toprevent the occurrence of the damaging effects of lightning by prayers. Priestsprayed,

"temper the destruction of hail and cyclones and the force of tempestsand lightning; check hostile thunders and great winds; and cast downthe spirits of storms and the powers of the air."

Peter Ahlwardts ("Reasonable and Theological Considerations about Thunderand Lightning", 1745) advised individuals seeking cover from lightning to goanywhere except in or around a church.[6] In Europe, the lightning rod mayhave been independently invented by Czech priest Václav Prokop Divišbetween 1750 to 1754.

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Franklin’s earliest papers on electricity[3]

United States

In the United States, the pointed lightning rod conductor, also called a"lightning attractor" or "Franklin rod," was invented by BenjaminFranklin in 1749 as part of his groundbreaking explorations of electricity.Although not the first to suggest a correlation between electricity andlightning, Franklin was the first to propose a workable system for testing hishypothesis.[7] Franklin speculated that, with an iron rod sharpened to a pointat the end,

"The electrical fire would, I think, be drawn out of a cloud silently,before it could come near enough to strike...."

Franklin speculated about lightning rods for several years before his reportedkite experiment. This experiment, in fact, took place because he was tired ofwaiting for Christ Church in Philadelphia to be completed so he could place alightning rod on top of it.

In the 19th century, the lightning rod became a decorative motif. Lightningrods were embellished with ornamental glass balls[8] (now prized bycollectors). The ornamental appeal of these glass balls has been used inweather vanes. The main purpose of these balls, however, is to provideevidence of a lightning strike by shattering or falling off. If after a storm aball is discovered missing or broken, the property owner should then check the building, rod, and grounding wire fordamage.

Balls of solid glass occasionally were used in a method purported to prevent lightning strikes to ships and otherobjects. The idea was that glass objects, being non-conductors, are seldom struck by lightning. Therefore, goes thetheory, there must be something about glass that repels lightning. Hence the best method for preventing a lightningstrike to a wooden ship was to bury a small solid glass ball in the tip of the highest mast. The random behavior oflightning combined with observers' confirmation bias ensured that the method gained a good bit of credence evenafter the development of the marine lightning rod soon after Franklin's initial work.

The first lightning conductors on ships were supposed to be hoisted when lightning was anticipated, and had a lowsuccess rate. In 1820 William Snow Harris invented a successful system for fitting lightning protection to thewooden sailing ships of the day, but despite successful trials which began in 1830, the British Royal Navy did notadopt the system until 1842, by which time the Imperial Russian Navy had already adopted the system.Nikola Tesla's U.S. Patent 1,266,175 [9] was an improvement in lightning protectors. The patent was granted due to afault in Franklin's original theory of operation; the pointed lightning rod actually ionizes the air around itself,rendering the air conductive, which in turn raises the probability of a strike. Many years after receiving his patent, in1919 Dr. Tesla wrote an article for The Electrical Experimenter entitled "Famous Scientific Illusions", in which heexplains the logic of Franklin's pointed lightning rod and discloses his improved method and apparatus.DuPont Explosives manufacturing sites were surrounded by pine trees. The needles on many pine trees can act astens of thousands of points for higher voltages to flow current into the air and lower the difference between the cloudto ground, and reduce the number of strikes per square mile of area. During the 1950s, DuPont made nitroglycerin insome buildings and moved it in "Angel Buggies" to the packing building. Employees at those sites were verysensitive to potential lightning strikes.[10]

In the 1990s, the 'lightning points' were replaced as originally constructed when the statue of Freedom atop the United States Capitol building in Washington, D.C. was restored.[11] The statue was designed with multiple devices that are tipped with platinum. The Washington Monument also was equipped with multiple lightning points,[12] and

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the Statue of Liberty in New York Harbor gets hit with lightning which is grounded out.

Structure protectors

Landscape suited for purpose of explanation: (1) Represents Lord Kelvin's "reduced" area of the region;[13] (2) Surface concentric with the Earthsuch that the quantities stored over it and under it are equal; (3) Building on a site of excessive electrostatic charge density; (4) Building on a site of

low electrostatic charge density. (Image via U.S. Patent 1266175 [14].)

Lightning diversion

Lightning rod mounted at The HolyMonastery of St. Nicholas Anapausas

(Μονή του Αγίου Νικολάου), Meteora,Greece

Lightning rods convey the current from a strike to the ground or water via alow-resistance conductor. A lightning strike is thus said to be diverted fromthe protected structure. However, diversion is a misnomer. Rather, thelightning rod widely used attracts and intercepts a strike that terminates near aprotected structure.[15] There is some uncertainty as to why a lightning strikeis attracted to a lightning rod or similar protector, the leading assumptionbeing that the air near the rod becomes ionized during an electrical storm, andthus highly conductive relative to the surrounding air.[15]

Lightning arrester

In telegraphy and telephony, a lightning arrester is placed where wires enter astructure, preventing damage to electronic instruments within and ensuringthe safety of individuals near them. Lightning arresters, also called surgeprotectors, are devices that are connected between each electrical conductorin a power and communications systems and the Earth. These provide a shortcircuit to the ground that is interrupted by a non-conductor, over whichlightning jumps. Its purpose is to limit the rise in voltage when acommunications or power line is struck by lightning.

The non-conducting material may consist of a semi-conducting material suchas silicon carbide or zinc oxide, or a spark gap. Primitive varieties of such spark gaps are simply open to the air, butmore modern varieties are filled with dry gas and have a small amount of radioactive material to encourage the gasto ionize when the voltage across the gap reaches a specified level. Other designs of lightning arresters use aglow-discharge tube (essentially like a neon glow lamp) connected between the protected conductor and ground, orvoltage-activated solid-state switches called varistors or MOVs. Lightning arresters built for substation use areimpressive devices, consisting of a porcelain tube several feet long and several inches in diameter, filled with disksof zinc oxide. A safety port on the side of the device vents the occasional internal explosion without shattering theporcelain cylinder.'

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Electric power system lightning protectionHigh-tension power lines carry a lighter conductor (sometimes called a 'pilot' or 'shield') wire over the main powerconductors. This conductor is grounded at various points along the link, or insulated from the tower structures bysmall insulators that are easily jumped by lightning voltages. The latter allows the pilot wire to be used forcommunications purposes, or to carry current for aircraft clearance lights. Electrical substations may have a web ofgrounded wires covering the whole plant.

Lightning protection of mast radiatorsMast radiators are insulated from the ground by a gap at the base. When lightning hits the mast, it jumps this gap. Asmall inductivity in the feed line between the mast and the tuning unit (usually one winding) limits the voltageincrease, protecting the transmitter from dangerously high voltages. The transmitter must be equipped with a deviceto monitor the antenna's electrical properties. This is very important, as a charge could remain after a lightning strike,damaging the gap or the insulators. The monitoring device switches off the transmitter when the antenna showsincorrect behavior, e.g. as a result of undesired electrical charge. When the transmitter is switched off, these chargesdissipate. The monitoring device makes several attempts to switch back on. If after several attempts the antennacontinues to show improper behavior, possibly as result of structural damage, the transmitter remains switched off.

Lightning conductors and grounding precautions

Example of a grounding system that failed during alightning strike resulting in a fire.

Ideally, the underground part of the assembly should reside in anarea of high ground conductivity. If the underground cable is ableto resist corrosion well, it can be covered in salt to improve itselectrical connection with the ground. While the electricalresistance of the lightning conductor between the air terminal andthe Earth is concerning, the inductive reactance of the conductorcould be more important. For this reason, the down conductorroute is kept short, and any curves have a large radius. If thesemeasures are not taken, lightning current may arc over anobstruction, resistive or reactive, that it encounters in theconductor. At the very least, the arc current will damage thelightning conductor and can easily find another conductive path,such as building wiring or plumbing, and cause fires or otherdisasters. Grounding systems without low resistivity to the groundcan still be effective in protecting a structure from lightningdamage. When ground soil has poor conductivity, is very shallow,or non-existent, a grounding system can be augmented by addingground rods, counterpoise (ground ring) conductor, cable radialsprojecting away from the building, or a concrete building'sreinforcing bars can be used for a ground conductor (UferGround). These additions, while still not reducing the resistance ofthe system in some instances, will allow the dissipation of thelightning into the earth without damage to the structure.[16]

Additional precautions must be taken to prevent side-flashes between conductive objects on or in the structure andthe lightning protection system. The surge of lightning current through a lightning protection conductor will create a

voltage difference between it and any conductive objects that are near it. This voltage difference can be large enough to cause a dangerous side-flash (spark) between the two that can cause significant damage, especially on structures

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housing flammable or explosive materials. The most effective way to prevent this potential damage is to ensure theelectrical continuity between the lightning protection system and any objects susceptible to a side-flash. Effectivebonding will allow the voltage potential of the two objects to rise and fall in tandem, thereby eliminating any risk ofa side-flash.[17]

Lightning protection system designConsiderable material is used to make up lightning protection systems, so it is prudent to consider carefully where arod structure will have the greatest effect. Historical understanding of lightning, from statements made by BenFranklin,[18] assumed that each device protected a cone of 45 degrees.[19] This has been found to be unsatisfactoryfor protecting taller structures, as it is possible for lightning to strike the side of a building.A better technique to determine the effect of a new arrester is called the "rolling sphere technique" and wasdeveloped by Dr Tibor Horváth. To understand this requires knowledge of how lightning 'moves'. As the step leaderof a lightning bolt jumps toward the ground, it steps toward the grounded objects nearest its path. The maximumdistance that each step may travel is called the critical distance and is proportional to the electrical current. Objectsare likely to be struck if they are nearer to the leader than this critical distance. It is standard practice to approximatethe sphere's radius as 46 m near the ground.[20]

An object outside the critical distance is unlikely to be struck by the leader if there is a solidly grounded objectwithin the critical distance. Locations that are considered safe from lightning can be determined by imagining aleader's potential paths as a sphere that travels from the cloud to the ground. For lightning protection, it suffices toconsider all possible spheres as they touch potential strike points. To determine strike points, consider a sphererolling over the terrain. At each point, we are simulating a potential leader position. Lightning is most likely to strikewhere the sphere touches the ground. Points that the sphere cannot roll across and touch are safest from lightning.Lightning protectors should be placed where they will prevent the sphere from touching a structure. A weak point inmost lightning diversion systems is in transporting the captured discharge from the lightning rod to the ground,though.[21] Lightning rods are typically installed around the perimeter of flat roofs, or along the peaks of slopedroofs at intervals of 6.1 m or 7.6 m, depending on the height of the rod.[22] When a flat roof has dimensions greaterthan 15 m by 15 m, additional air terminals will be installed in the middle of the roof at intervals of 15 m or less in arectangular grid pattern.[23]

Should a lightning rod have a point?This was a controversy as early as the 18th century. In the midst of political confrontation between Britain and itsAmerican colonies, British scientists maintained that a lightning rod should have a ball on its end. Americanscientists maintained that there should be a point. As of 2003, the controversy had not been completely resolved.[24]

It is difficult to resolve the controversy because proper controlled experiments are nearly impossible in such work; inspite of the work of Moore, et al. [described below] most lightning rods seen on buildings have sharp points. Workperformed by Charles B. Moore, et al.[25], in 2000 has helped this issue, finding that moderately rounded orblunt-tipped lightning rods act as marginally better strike receptors. [described below] As a result, round-tipped rodsare installed the majority of the time on new systems in the United States. To quote:

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Nikola Tesla's"Lightning-Protector"

U.S. Patent 1266175 [14]; An early typeof dissipater-arrester, which the patent

states serves to prevent and safelydissipate lightning strikes

Calculations of the relative strengths of the electric fields abovesimilarly exposed sharp and blunt rods show that while the fields aremuch stronger at the tip of a sharp rod prior to any emissions, theydecrease more rapidly with distance. As a result, at a few centimetersabove the tip of a 20-mm-diameter blunt rod, the strength of the field isgreater than over an otherwise similar, sharper rod of the same height.Since the field strength at the tip of a sharpened rod tends to be limitedby the easy formation of ions in the surrounding air, the field strengthsover blunt rods can be much stronger than those at distances greaterthan 1 cm over sharper ones.

The results of this study suggest that moderately blunt metal rods (withtip height to tip radius of curvature ratios of about 680:1) are betterlightning strike receptors than sharper rods or very blunt ones.

In addition, the height of the lightning protector relative to the structure to beprotected and the Earth itself will have an effect.[26][27]

Lightning dissipation

Lightning dissipators have been widely discredited and criticized bylightning researchers over the last 30 years. These terminals (known as Dissipation Array Systems, and ChargeTransfer Systems) claim to make a structure less attractive to lightning and other charges that flow through theEarth's atmosphere around it. These generally encompass systems and equipment for the preventative protection ofobjects located on the surface of the earth from the effects of atmospherics. The devices are alleged to deal with thephenomena such as electrostatic fields, electromagnetic fields, field transients, static charges, and any other relatedatmospheric electricity phenomena.

Individual dissipator rods may appear as slightly-blunted metal spikes sticking out in all directions from a metalconductor.[28] These elements are mounted on short metal arms at the top of a radio antenna or tower, the area mostlikely to be struck. The dissipation theory states an alteration in the potential difference (voltage) between thestructure and the storm cloud miles above theoretically reduces but does not eliminate risk of lightning strikes.[29]

Various manufacturers make these claims. Induced upward lightning strikes occurring on tall structures (effectiveheights of 300 m or more) can be reduced by altering the shape of the structure.[30]

Evaluations and analysisA controversy over the assortment of operation theories dates back to the 18th century, when Franklin himself statedthat his lightning protectors protected buildings by dissipating electric charge. He later retracted the statement,stating that the device's exact mode of operation was something of a mystery at that point. Diversion is a misnomer;no modern systems are claimed to divert anything, but rather to intercept the charge that terminates on a structureand carry it to the ground. The energy in a lightning strike is measured in joules. The reason that lightning doesdamage is that this energy is released in a matter of microseconds (typically 30 to 50 microseconds). If the sameenergy could be released slowly over a period of many seconds or minutes, the current flow would be inmilliamperes or a few amperes at most. This is the intent of charge dissipation.[31]

The dissipation theory states that a lightning strike to a structure can be prevented by altering the electrical potential between the structure and the thundercloud. This is done by transferring electric charge (such as from the nearby Earth to the sky or vice versa).[29][32] Transferring electric charge from the Earth to the sky is done by erecting some sort of tower equipped with one or more sharply pointed protectors upon the structure. It is noted that sharply pointed objects will indeed transfer charge to the surrounding atmosphere[33][34] and that a considerable electric

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current through the tower can be measured when thunderclouds are overhead.Lightning strikes to a metallic structure can vary from leaving no evidence excepting perhaps a small pit in the metalto the complete destruction of the structure (Rakov, Page 364).[35] When there is no evidence, analyzing the strikes isdifficult. This means that a strike on an uninstrumented structure must be visually confirmed, and the randombehavior of lightning renders such observations difficult.[35][36][37][38] There are also inventors working on thisproblem,[39][40] such as through a lightning rocket. While controlled experiments may be off in the future, very gooddata is being obtained through techniques which use radio receivers that watch for the characteristic electrical'signature' of lightning strikes using fixed directional antennas.[41][42][43][44] Through accurate timing andtriangulation techniques, lightning strikes can be located with great precision, so strikes on specific objects often canbe confirmed with confidence.The introduction of lightning protection systems into standards allowed various manufactures to develop protectorsystems to a multitude of specifications and there are various lightning rodstandards.[45][46][47][48][49][50][51][52][53][54] The NFPA's independent third party panel found that "the [EarlyStreamer Emission] lightning protection technology appears to be technically sound" and that there was an "adequatetheoretical basis for the [Early Streamer Emission] air terminal concept and design from a physical viewpoint".(Bryan, 1999[55]) The same panel also concluded that "the recommended [NFPA 780 standard] lightning protectionsystem has never been scientifically or technically validated and the Franklin rod air terminals have not beenvalidated in field tests under thunderstorm conditions." In response, the American Geophysical Union concluded that"[t]he Bryan Panel reviewed essentially none of the studies and literature on the effectiveness and scientific basis oftraditional lightning protection systems and was erroneous in its conclusion that there was no basis for the Standard."AGU did not attempt to assess the effectiveness of any proposed modifications to traditional systems in its report.[56]

No major standards body, such as the NFPA or UL, has currently endorsed a device that can prevent or reducelightning strikes. The NFPA Standards Council, following a request for a project to address Dissipation ArraySystems and Charge Transfer Systems, denied the request to begin forming standards on such technology (thoughthe Council did not foreclose on future standards development after reliable sources demonstrating the validity of thebasic technology and science were submitted).[57] Members of the Scientific Committee of the InternationalConference on Lightning Protection has issued a joint statement stating their opposition to dissipater technology.[58]

Various investigators believe the natural downward lightning strokes to be unpreventable.[30] Since most lightningprotectors' ground potentials are elevated, the path distance from the source to the elevated ground point will beshorter, creating a stronger field (measured in volts per unit distance) and that structure will be more prone toionization and breakdown.[59] Scientists from the National Lightning Safety Institute claim that these dissipationdevices are nothing more than expensive lightning protectors and that they, unlike traditional methods, are not basedon "scientifically proven and indisputable technical arguments".[60] William Rison states that in his opinion theunderlying theory of dissipation is "scientific nonsense".[61] According to these sources, there is no proof that thedissipation arrangement is at all effective. According to opponents of the dissipation technology, the various designsof dissipaters indirectly "eliminate" lightning via the alteration of a building's shape and only have a small effect(either intended or not) because there is no significant reduction to the susceptibility of a structure to the generationof upward lightning strokes.[30] Some field investigations of dissipaters show that their performance is comparable toconventional terminals and possess no great enhancement of protection. According to these field studies, thesedevices have not shown that they totally eliminated lightning strikes.[62]

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Aircraft protectorsLightning protection for aircraft is provided by mounting devices on the aircraft structure. The protectors areprovided with extensions through the structure of the aircraft's outer surface and within a static discharger. Protectionsystems for use in aircraft must protect critical and non-critical electronic equipment. Aircraft lightning protectionprovides an electrical path having a plurality of conductive segments, continuous or discontinuous, that uponexposure to a high voltage field form an ionization channel due to the system's breakdown voltage. Various lightningprotection systems must reject the surge currents associated with the lightning strikes. Lightning protection meansfor aircraft include components which are dielectrics and metallic layers applied to the ordinarilylightning-accessible surfaces of composite structures. Various ground connection means to the layers comprises asection of wire mesh fusing the various layers to an attachment connecting the structure to an adjacent groundstructure. Composite-to-metal or composite-to-composite structural joints are protected by making the interface areasconductive for transfer of lightning current.Some aircraft lightning protection systems use a shielded cable system. These systems consist of one or moreconductors enclosed by a conductive shield. The cable has both conductors of one end connected to a groundingelement. This is intended to provide protection from electromagnetic interference. Such systems reduce theelectromagnetically induced voltage in a shielded conductor. This is intended to provide protection against inducedelectromagnetic interference from lightning. This network provides a normally-high impedance which breaks downto a very low impedance in response to a momentary voltage surge electromagnetically induced in the shield. Thisestablishes a conductive path between the shield and ground. Any surge voltage from lightning creates a currentthrough the cable. This results in an electromagnetic field of the opposite direction, which cancels or reduces themagnitude of the electromagnetic field within the shielded cable.

Watercraft protectorsA lightning protection installation on a watercraft comprises a lightning protector mounted on the top of the mast orsuperstructure and a grounding conductor in contact with the water. Electrical conductors attach to the protector andrun downward to the conductor. For a vessel with a conducting (iron or steel) hull, the grounding conductor is thehull. For a vessel with a non-conducting hull, the grounding conductor may be retractable, part of the hull, orattached to a centerboard.

Notes[1] Jernegan, M. W. (1928). "Benjamin Franklin's "Electrical Kite" and Lightning Rod". The New England Quarterly (The New England

Quarterly) 1 (2): 180–196. doi:10.2307/359764. JSTOR 359764.[2] See the following two articles for conflicting views of this being an independent invention by Diviš:

Hujer, Karel (December 1952). "Father Procopius Diviš — The European Franklin". Isis 43 (4): 351–357. doi:10.1086/348159.ISSN 0021-1753. JSTOR 227388.Cohen, I. Bernard; Schofield, Robert (December 1952). "Did Diviš Erect the First European Protective Lightning Rod, and Was His InventionIndependent?". Isis 43 (4): 358–364. doi:10.1086/348160. ISSN 0021-1753. JSTOR 227389.

[3] I. Bernard Cohen, The Two Hundredth Anniversary of Benjamin Franklin's Two Lightning Experiments and the Introduction of the LightningRod, in: Proceedings of the American Philosophical Society, Vol. 96, No. 3. (Jun. 20, 1952), pp. 331–366.

[4] The office of the first Russian oligarch (http:/ / www. itogi. ru/ archive/ 2002/ 42/ 102260. html) (Russian)[5] "History of Rebar" (http:/ / www. whaleysteel. com/ rebar-news/ 83-history-of-rebar). Whaley Steel. .[6] Seckel, Al, and John Edwards, " Franklin's Unholy Lightning Rod (http:/ / www. evolvefish. com/ freewrite/ franklgt. htm)". 1984.[7] Recovering Benjamin Franklin: an exploration of a life of science and service (http:/ / books. google. com/ ?id=hySRKOq8sBQC&

pg=PA59& dq=Benjamin+ Franklin+ lightning+ rod+ 1749#v=onepage& q& f=false). Open Court Publishing. 1999. ISBN 9780812693874. .[8] " Antique Lightning Rod Ball Hall of Fame (http:/ / www. antiquebottles. com/ lightningrod/ fame. html)". Antique Bottle Collectors Haven.

(glass lightning balls collection)[9] http:/ / www. google. com/ patents?vid=1,266,175[10] Zipse, D., Advancement of lightning protection and prevention in the 20th century. Industry Applications Magazine, IEEE, Volume 14,

Issue 3, May-June 2008 Pg 12 - 15.[11] Statue of Freedom http:/ / www. aoc. gov/ cc/ art/ freedom. cfm

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[12] The Point of a Monument: A History of the Aluminum Cap of the Washington Monument: The Functional Purpose (http:/ / www. tms. org/pubs/ journals/ JOM/ 9511/ Binczewski-9511. html#RTFToC5)

[13] Sir William Thomson, Papers on Electrostatics and Magnetism.[14] http:/ / www. google. com/ patents?vid=1266175[15] U.S. Patent 1,266,175 – Tesla, "Lightning-Protector"[16] NFPA-780 Standard for the Installation of Lightning Protection Systems 2008 Edition - Annex B - B.4.3[17] NFPA-780 Standard for the Installation of Lightning Protection Systems 2008 Edition - Annex C[18] High-voltage surge eliminator, Roy B. Carpenter, Jr., U.S. Patent 5532897 (http:/ / www. google. com/ patents?vid=5532897). Page 1,

Column 1, Line 26-27.[19] Donlon, Tim, " Lightning Protection for Historic Buildings (http:/ / www. buildingconservation. com/ articles/ lightning/ lightn. htm)".

Cathedral Communications Limited, 2001.[20] Installation requirements for lightning protection systems - UL 96A 4.7.3.4.2[21] Lightning protection installation, U.S. Patent 3919956 (http:/ / www. google. com/ patents?vid=3919956)[22] Installation requirements for lightning protection systems - UL 96A 8.2.2[23] Standard for the installation of lightning protection systems 2008 edition - NFPA-780 4.8.2.4[24] Ian Godwin (March 26, 2003). "Franklin letter to King fans flames of lightning debate" (http:/ / www. abc. net. au/ science/ articles/ 2003/

03/ 26/ 816484. htm). ABC Science Online. Australian Broadcasting Corporation. . Retrieved July 29, 2011.[25] C. B. Moore, William Rison, James Mathis, and Graydon Aulich, " Lightning Rod Improvement Studies (http:/ / ams. allenpress. com/

amsonline/ ?request=get-abstract& issn=1520-0450& volume=039& issue=05& page=0593)". Journal of Applied Meteorology: Vol. 39, No.5, pp. 593–609. Langmuir Laboratory for Atmospheric Research, New Mexico Institute of Mining and Technology, Socorro, New Mexico.April 10, 1999.

[26] U.S. Patent 1266175 (http:/ / www. google. com/ patents?vid=1266175), Tesla, "Lightning-Protector".[27] U.S. Patent 3371144 (http:/ / www. google. com/ patents?vid=3371144), Griscom, "Transmission-line lightning-proofing structures". Page

25, Column 5. (cf. [...] the charge on a leader as a function of height above ground[...])[28] U.S. Patent D478,294 (http:/ / www. google. com/ patents?vid=D478,294) - Haygood, "Lightning dissipation assembly "[29] U.S. Patent 6307149 (http:/ / www. google. com/ patents?vid=6307149), Richard Ralph Zini, et al., Non-contaminating lightning protection

system. Claim one and claim ten.[30] Mousa, Abdul M. "The applicability of Lightning Elimination Devices to Substations and Power Lines". British Columbia Hydro, Burnaby,

British Columbia, Canada V3N 4X8.[31] RB Carpenter Jr., Dissipation array systems for lightning protection. US Patent 5,043,527[32] John Richard Gumley, U.S. Patent 6320119 (http:/ / www. google. com/ patents?vid=6320119), Lightning air terminals and method of

design and application[33] Emitter of ions for a lightning rod with a parabolic reflector, Manuel Domingo Varela, U.S. Patent 6069314 (http:/ / www. google. com/

patents?vid=6069314).[34] Lightning-protector for electrical conductors, Johathan H. Vail, U.S. Patent 357050 (http:/ / www. google. com/ patents?vid=357050).[35] Rakov, et al., Lightning: physics and effects[36] Martin A. Uman, Lightning Discharge (http:/ / books. google. com/ books?vid=ISBN0486414639& id=9AaG3JnpfcgC). Courier Dover

Publications, 2001. 377 pages. ISBN 0486414639[37] Donald R. MacGorman, The Electrical Nature of Storms (http:/ / books. google. com/ books?vid=ISBN0195073371& id=_NbHNj7KJecC).

Oxford University Press (US), 1998. 432 pages. ISBN 0195073371[38] Hans Volland, Handbook of Atmospheric Electrodynamics, Volume I (http:/ / books. google. com/ books?vid=ISBN0849386470&

id=MNPPh7B3WTIC). CRC Press, 1995. 408 pages. ISBN 0849386470[39] Method and apparatus for the artificial triggering of lightning, Douglas A. Palmer, U.S. Patent 6012330 (http:/ / www. google. com/

patents?vid=6012330)[40] Lightning rocket, Robert E. Betts, U.S. Patent 6597559 (http:/ / www. google. com/ patents?vid=6597559)[41] Lightning locating system, Ralph J. Markson et al., U.S. Patent 6246367 (http:/ / www. google. com/ patents?vid=6246367).[42] Lightning locating system, Airborne Research Associates, Inc., U.S. Patent 5771020 (http:/ / www. google. com/ patents?vid=5771020).[43] System and method of locating lightning strikes, The United States of America as represented by the Administrator of the National

Aeronautics and Space Administration, U.S. Patent 6420862 (http:/ / www. google. com/ patents?vid=6420862)[44] Single station system and method of locating lightning strikes, The United States of America as represented by the United States National

Aeronautics and Space Administration, U.S. Patent 6552521 (http:/ / www. google. com/ patents?vid=6552521).[45] NFPA-780 Standard for the Installation of Lightning Protection Systems[46] LPI-175 Standard of Practice for the Design - Installation - Inspection of Lightning Protection Systems[47] M440.1-1, Electrical Storms and Lightning Protection, Department of Energy[48] AFI 32-1065 - Grounding Systems, U. S. Air Force Space Command[49] Motorola R-56 Standards and Guidance for Communications Sites[50] FAA STD 019e, Lightning and Surge Protection, Grounding, Bonding and Shielding Requirements for Facilities and Electronic Equipment[51] IEEE STD 142, Grounding of Industrial and Commercial Power Systems[52] IEEE STD 1100, Powering and Grounding Electronic Equipment

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[53] Lightning Protection Systems (http:/ / www. ul. com/ lightning/ ), UL's Lightning Protection program, Underwriters Laboratories[54] IEC 62305 Series of lightning protection guidelines[55] Bryan, R. G., et al., "Report of the Third-Party Independent Evaluation Panel on the Early Streamer Emission Lightning Protection

Technology".[56] Report of The Committee on Atmospheric And Space Electricity of The American Geophysical Union on The Scientific Basis for

Traditional Lightning Protection Systems (http:/ / www. agu. org/ focus_group/ ASE/ NFPAreport. pdf)[57] Casey C. Grant, " To: Interested Parties (http:/ / www. lightningsafetyalliance. com/ documents/ das_cts. pdf)"[58] Mousa, Abdul M. "Scientists Oppose Early Streamer Air Terminals", 1999.[59] U.S. Patent 1869661 (http:/ / www. google. com/ patents?vid=1869661), Bumbraugh, "Lightning protection system and method".[60] Mousa, Abdul M. (1999). "Scientists Oppose Early Streamer Air Terminals" (http:/ / www. lightningsafety. com/ nlsi_lhm/

charge_transfer_opp. html). National Lightning Safety Institute (http:/ / www. lightningsafety. com). . Retrieved 2006-09-18.[61] Rison, William (2001). "There Is No Magic To Lightning Protection: Charge Transfer Systems Do Not Prevent Lightning Strikes" (http:/ /

www. lightningsafety. com/ nlsi_lhm/ magic. pdf) (pdf). National Lightning Safety Institute (http:/ / www. lightningsafety. com). . Retrieved2006-09-18.

[62] Rison, W., Moore, C.B., and Aulich, G.D., "Lightning air terminals - is shape important?", Electromagnetic Compatibility, 2004. EMC2004. 2004 InternationalSymposium on Volume 1, 9–13 August 2004 Page(s):300 - 305 vol.1

References• Vladimir A. Rakov and Martin A. Uman, Lightning: physics and effects (http:/ / books. google. com/

books?vid=ISBN0521583276& id=NviMsvVOHJ4C). Cambridge University Press, 2003. 698 pages. ISBN0521583276

• J. L. Bryan, R. G. Biermann and G. A. Erickson, "Report of the Third-Party Independent Evaluation Panel on theEarly Streamer Emission Lightning Protection Technology". National Fire Protection Association, Quincy, Mass.,1999.

• Kithil, Rich. "More on lightning rods...", Lightning Safety Home Page, Message #402. May 8, 2000. (Response toC. B. Moore) Originally at: http:/ / www. thomson. ece. ufl. edu/ lightning/ Moore%20on%20air%20terminals.htm

• M. A. Uman and V. A. Rakov " Critical Review of Nonconventional Approaches to Lightning Protection (http:/ /www. lightningsafety. com/ nlsi_lhm/ Uman_Rakov. pdf)", Bulletin of the American Meteorological Society,December 2002.

• Mousa, Abdul M. " War of the Lightning Rods (http:/ / www. lightningsafetyalliance. com/ documents/lightning_war. pdf)", Electricity Today, 2004.

• Zipse, Donald. " Prevent Lightning Strikes with Charge Transfer Systems (http:/ / www. powerquality. com/ mag/power_prevent_lightning_strikes/ index. html)", Power Quality, November 2001

• Zipse, Donald. "Lightning protection methods: An update and a discredited system vindicated", IEEE Trans. onIndustry Applications, 37, 407-414, 2001.

• Carpenter, Jr., Roy B. " Preventing Direct Strikes (http:/ / lecglobal. com/ info/ tech-papers/preventing-direct-lightning-strikes. pdf)".

External links• " Researchers find that blunt lightning rods work best (http:/ / www. usatoday. com/ weather/ resources/ basics/

2000-05-15-lightn-rod-tests. htm)". USA Today. (06/10/2002)• Federal Aviation Administration, " FAA-STD-019d, Lightning and surge protection, grounding, bonding and

shielding requirements for facilities and electronic equipment (http:/ / ntl. bts. gov/ card_view.cfm?docid=22344)". National Transportation Library (http:/ / ntl. bts. gov/ ), 2002-08-09.

• Kithil, Richard, " Lightning Rods: Recent Investigations (http:/ / www. lightningsafety. com/ nlsi_lhm/lightning_rod_recent. html)". National Lightning Safety Institute (http:/ / www. lightningsafety. com/ ),September 26, 2005.

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• Kithil, Richard, " Should Lightning Rods be Installed? (http:/ / www. lightningsafety. com/ nlsi_lhm/ InstallRods.html)". National Lightning Safety Institute, September 26, 2005.

• Kithil, Richard, " Fundamentals of Lightning Protection (http:/ / www. lightningsafety. com/ nlsi_lhm/ lpts.html)". National Lightning Safety Institute, September 26, 2005.

• Nailen, Richard L., " Lightning controversy goes on (http:/ / www. findarticles. com/ p/ articles/ mi_qa3726/is_200102/ ai_n8940245)", The Electrical Apparatus, February 2001.

• Lightning Safety Alliance education (http:/ / www. lightningsafetyalliance. com/ education. html) page• Richard Owen, Wm S Orr, John Radford Young, Alexander Jardine, Robert Gordon Latham, Edward Smith,

William Sweetland Dallas, Orr's Circle of the Sciences, Atmospheric Electricity—Theory of Lightning-rods(http:/ / books. google. com/ books?id=Xcg4AAAAMAAJ& pg=PA232) W.S. Orr 1855.

• February 1919 Popular Science article about Lightning Arresters and how they were used in early AC and DCpower distribution systems, Electrical Devices and How They Work, Part 14: Lightning Arresters, PopularScience monthly, February 1919, 5 unnumbered pages, Scanned by Google Books: http:/ / books. google. com/books?id=7igDAAAAMBAJ& pg=PT17

Article Sources and Contributors 13

Article Sources and ContributorsLightning rod  Source: http://en.wikipedia.org/w/index.php?oldid=471490015  Contributors: Agathman, Ahoerstemeier, Ajraddatz, Alansohn, Ali ringo, Ali@gwc.org.uk, AmateurEditor,Amorymeltzer, Andrew73, Antandrus, Ante84, Arch dude, Arjun01, Auric, BD2412, Bartimaeus, Bear in shapka, Beetstra, Beland, Bemoeial, Bendy660, Bj2021, Bmicomp, Bn, Bob Palin,Bobmack89x, Bobo192, Bradeos Graphon, Buddy23Lee, Cabreet, Can't sleep, clown will eat me, CanadianLinuxUser, CanisRufus, Cast123, Charles Matthews, Chetvorno, Chubbles, Circeus,Coffee2theorems, CoolKoon, Copeland.James.H, CosmiCarl, Courcelles, CyrilB, DARTH SIDIOUS 2, DMahalko, DVD R W, Dagbrown, Dalklein, Dave souza, Davewild, Dogears,DragonflySixtyseven, Dreamyshade, Dsav, Dual Freq, DubaiTerminator, Dycedarg, Dzordzm, Eequor, Erik9, Etan J. Tal, Falcon8765, FearChild, Flffy'd, Frokeefe, Frotz, GS3, Gaius Cornelius,Gauthamdoha, Gene Nygaard, Glenn, Gogo Dodo, Grafen, Graham87, GreatWhiteNortherner, Greyhood, Gutza, HannesJvV, HappyInGeneral, HdeK, Hemanshu, Hluup, Hooperbloob,Hydroxonium, IPSOS, IVP, Iliev, IvanStepaniuk, J.delanoy, JediSaint, Jeff3000, JidGom, Joao Xavier, Joe Kress, John254, Johndarrington, Johnnymartins, Joyous!, Jung hyuk, Kchishol1970,Keith7384, Ken Gallager, Kinkyturnip, Kinsler33, Klonimus, Koavf, Kolbasz, Kozuch, Kreachure, Kubigula, Kungfuadam, Lauciusa, Leonard G., LessHeard vanU, Li-sung, Lightmouse,LightningLeader, Linnell, Lisatwo, LoopTel, Lord Cornwallis, LorenzoB, Madd4Max, Magister Mathematicae, Malleus Fatuorum, Mandarax, Marysunshine, Materialscientist, Mathiasrex,McGeddon, Melongrower, Michael Devore, Mipadi, Missmarple, Msavidge, Mschlindwein, N0YKG, Najoj, NathanHurst, NawlinWiki, Ngmarle, NickCT, Nihiltres, Ohnoitsjamie, Omegatron,Onceler, Ortolan88, Packare, Philip Trueman, Philsy, Physicistjedi, Piano non troppo, Pil56, Pinche veto, Plastikspork, Poccil, Pollinator, Pooja123456789abc, Poompt, Prime, QuinnJL, Quintote,R'n'B, Racingstripes, Reddi, Rich Farmbrough, RichiH, Rico402, Rjwilmsi, Rossami, Rostin, Rumping, SCEhardt, Schmendrik881, Shadow1, Shirik, Shirulashem, Shoy, Sietse Snel, Sjö,SkyWalker, SmartGuy, Smithck0, Snek01, Snigbrook, Some jerk on the Internet, Squids and Chips, Srleffler, Srlnkn, Steve Quinn, Svonkie, Syncategoremata, TAnthony, Tangotango, Tbone762,Tcncv, Tdreyer1, Teleomatic, Teles, The Thing That Should Not Be, Tide rolls, Tinky1878, Torindkflt, Tr00st, Tulkolahten, Twilsonb, Uusitunnus, Vanessaezekowitz, Vicki Rosenzweig,Wackjum, WayneConrad, Wdchk, Weedwhacker128, Whisky drinker, WikHead, Wikibofh, Wikid77, Woohookitty, Wtshymanski, Xiaphias, Y control, Yamaguchi先 生, Yoganate79,Zahartono, Zamphuor, Zapvet, Ztara, 509 anonymous edits

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