Lightning rod
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A lightning rod (US, AUS) or lightning conductor (UK) is a metal rod or conductor mounted on top of a building and electrically connected to the ground through a wire, to protect the building in the event of lightning. Individual lightning rods are sometimes called finials, air terminals or strike termination devices.
If lightning targets the building it will preferentially strike the rod or rods, and be conducted to ground through the wire, instead of passing through the building, where it could start a fire or cause electrocution. A lightning rod is a single component in a lightning protection system.
In some instances, a metallic rod, taller than the building, is installed in the walls of the building during its construction. One end of the rod is kept out in the air and the other is buried deep in the ground.
In addition to rods placed at regular intervals on the highest portions of a structure, a lightning protection system typically includes a rooftop network of conductors, multiple conductive paths from the roof to the ground, bonding connections to metallic objects within the structure and a grounding network. The rooftop lightning rod is a metal strip or rod, usually of copper or aluminum. Lightning protection systems are installed on structures, trees, monuments, bridges or water vessels to minimize damage from lightning.
The lightning rod was invented by Benjamin Franklin in the Americas in 1749[1] and, perhaps independently, by Prokop Diviš in Europe in 1754.[2]
History
As buildings became taller, lightning becomes more of a threat. Lightning can damage structures made of most materials (masonry, wood, concrete and steel) as the huge currents involved can heat materials, causing a potential for fire, and also water to high temperatures.
Asia
Some of the most ancient lightning conductors can be found in Sri Lanka in places like the Anuradhapura Kingdom that dates back thousands of years. The Sinhalese kings, who mastered construction of stupas and advanced building structures, installed a metal tip made of silver or copper on the highest point of every building to conduct any lightning charge. In many parts of the world, ancient Buddhist monuments have been destroyed by lightning strikes, but not in Sri Lanka.[citation needed]
Russia
A lightning conductor may have been intentionally used in the Leaning Tower of Nevyansk. The spire of the tower is crowned with a metallic rod in the shape of a gilded sphere with spikes. This lightning rod is grounded through the rebar carcass, which pierces the entire building.
The Nevyansk Tower was built between 1725 and 1732, on the orders of industrialist Akinfiy Demidov. The Nevyansk Tower was built 25 years before Benjamin Franklin's experiment and scientific explanation.[4] However, the true intent behind the metal rooftop and rebars remains unknown.[5]
Europe
The church tower of many European cities, usually the highest structure, was the building often hit by lightning. Early on, Christian churches tried to prevent the occurrence of the damaging effects of lightning by prayers. Priests prayed,
- "temper the destruction of hail and cyclones and the force of tempests and lightning; check hostile thunders and great winds; and cast down the spirits of storms and the powers of the air."
Peter Ahlwardts ("Reasonable and Theological Considerations about Thunder and Lightning", 1745) advised individuals seeking cover from lightning to go anywhere except in or around a church.[6] In Europe, the lightning rod may have been independently invented by Czech priest Václav Prokop Diviš between 1750 to 1754.
United States
In the United States, the pointed lightning rod conductor, also called a "lightning attractor" or "Franklin rod," was invented by Benjamin Franklin in 1749 as part of his groundbreaking explorations of electricity. Although not the first to suggest a correlation between electricity and lightning, Franklin was the first to propose a workable system for testing his hypothesis.[7] Franklin speculated that, with an iron rod sharpened to a point at 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 reported kite experiment. This experiment, in fact, took place because he was tired of waiting for Christ Church in Philadelphia to be completed so he could place a lightning rod on top of it.
In the 19th century, the lightning rod became a decorative motif. Lightning rods were embellished with ornamental glass balls[8] (now prized by collectors). The ornamental appeal of these glass balls has been used in weather vanes. The main purpose of these balls, however, is to provide evidence of a lightning strike by shattering or falling off. If after a storm a ball is discovered missing or broken, the property owner should then check the building, rod, and grounding wire for damage.
Balls of solid glass occasionally were used in a method purported to prevent lightning strikes to ships and other objects. The idea was that glass objects, being non-conductors, are seldom struck by lightning. Therefore, goes the theory, there must be something about glass that repels lightning. Hence the best method for preventing a lightning strike to a wooden ship was to bury a small solid glass ball in the tip of the highest mast. The random behavior of lightning combined with observers' confirmation bias ensured that the method gained a good bit of credence even after 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 low success rate. In 1820 William Snow Harris invented a successful system for fitting lightning protection to the wooden sailing ships of the day, but despite successful trials which began in 1830, the British Royal Navy did not adopt 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 was an improvement in lightning protectors. The patent was granted due to a fault 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, in 1919 Dr. Tesla wrote an article for The Electrical Experimenter entitled "Famous Scientific Illusions", in which he explains 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 as tens of thousands of points for higher voltages to flow current into the air and lower the difference between the cloud to ground, and reduce the number of strikes per square mile of area. During the 1950s, DuPont made nitroglycerin in some buildings and moved it in "Angel Buggies" to the packing building. Employees at those sites were very sensitive to potential lightning strikes.[9]
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.[10] The statue was designed with multiple devices that are tipped with platinum. The Washington Monument also was equipped with multiple lightning points,[11] and the Statue of Liberty in New York Harbor gets hit with lightning which is grounded out.
Structure protectors
Lightning diversion
Lightning rods convey the current from a strike to the ground or water via a low-resistance conductor. A lightning strike is thus said to be diverted from the protected structure. However, diversion is a misnomer. Rather, the lightning rod widely used attracts and intercepts a strike that terminates near a protected structure.[13] There is some uncertainty as to why a lightning strike is attracted to a lightning rod or similar protector, the leading assumption being that the air near the rod becomes ionized during an electrical storm, and thus highly conductive relative to the surrounding air.[13]
Lightning arrester
In telegraphy and telephony, a lightning arrester is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them. Lightning arresters, also called surge protectors, are devices that are connected between each electrical conductor in a power and communications systems and the Earth. These prevent the flow of the normal power or signal currents to ground, but provide a path over which high-voltage lightning current flows, bypassing the connected equipment. Their purpose is to limit the rise in voltage when a communications or power line is struck by lightning or is near to a lightning strike.
A lightning arrester may be a spark gap or may have a block of a semi-conducting material such as silicon carbide or zinc oxide. Some spark gaps are open to the air, but more modern varieties are filled with dry gas and have a small amount of radioactive material to encourage the gas to ionize when the voltage across the gap reaches a specified level. Other designs of lightning arresters use a glow-discharge tube (essentially like a neon glow lamp) connected between the protected conductor and ground, or voltage-activated solid-state switches called varistors or MOVs. Lightning arresters built for substation use are impressive devices, consisting of a porcelain tube several feet long and several inches in diameter, filled with disks of zinc oxide. A safety port on the side of the device vents the occasional internal explosion without shattering the porcelain cylinder.
Lightning arresters are rated by the peak current they can withstand, the amount of energy they can absorb, and the breakover voltage that they require to begin conduction. They are applied as part of a lightning protection system, in combination with air terminals and bonding.
Electric power system lightning protection
High-tension power lines carry a lighter conductor (sometimes called a 'pilot' or 'shield') wire over the main power conductors. This conductor is grounded at various points along the link, or insulated from the tower structures by small insulators that are easily jumped by lightning voltages. The latter allows the pilot wire to be used for communications purposes, or to carry current for aircraft clearance lights. Electrical substations may have a web of grounded wires covering the whole plant.
Lightning protection of mast radiators
Mast radiators are insulated from the ground by a gap at the base. When lightning hits the mast, it jumps this gap. A small inductivity in the feed line between the mast and the tuning unit (usually one winding) limits the voltage increase, protecting the transmitter from dangerously high voltages. The transmitter must be equipped with a device to 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 shows incorrect behavior, e.g. as a result of undesired electrical charge. When the transmitter is switched off, these charges dissipate. The monitoring device makes several attempts to switch back on. If after several attempts the antenna continues to show improper behavior, possibly as result of structural damage, the transmitter remains switched off.
Lightning conductors and grounding precautions
Ideally, the underground part of the assembly should reside in an area of high ground conductivity. If the underground cable is able to resist corrosion well, it can be covered in salt to improve its electrical connection with the ground. While the electrical resistance of the lightning conductor between the air terminal and the Earth is concerning, the inductive reactance of the conductor could be more important. For this reason, the down conductor route is kept short, and any curves have a large radius. If these measures are not taken, lightning current may arc over an obstruction, resistive or reactive, that it encounters in the conductor. At the very least, the arc current will damage the lightning conductor and can easily find another conductive path, such as building wiring or plumbing, and cause fires or other disasters. Grounding systems without low resistivity to the ground can still be effective in protecting a structure from lightning damage. When ground soil has poor conductivity, is very shallow, or non-existent, a grounding system can be augmented by adding ground rods, counterpoise (ground ring) conductor, cable radials projecting away from the building, or a concrete building's reinforcing bars can be used for a ground conductor (Ufer Ground). These additions, while still not reducing the resistance of the system in some instances, will allow the dissipation of the lightning into the earth without damage to the structure.[14]
Additional precautions must be taken to prevent side-flashes between conductive objects on or in the structure and the 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 housing flammable or explosive materials. The most effective way to prevent this potential damage is to ensure the electrical continuity between the lightning protection system and any objects susceptible to a side-flash. Effective bonding will allow the voltage potential of the two objects to rise and fall in tandem, thereby eliminating any risk of a side-flash.[15]
Lightning protection system design
Considerable material is used to make up lightning protection systems, so it is prudent to consider carefully where a rod structure will have the greatest effect. Historical understanding of lightning, from statements made by Ben Franklin,[16] assumed that each device protected a cone of 45 degrees.[17] This has been found to be unsatisfactory for 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 was developed by Dr Tibor Horváth. To understand this requires knowledge of how lightning 'moves'. As the step leader of a lightning bolt jumps toward the ground, it steps toward the grounded objects nearest its path. The maximum distance that each step may travel is called the critical distance and is proportional to the electrical current. Objects are likely to be struck if they are nearer to the leader than this critical distance. It is standard practice to approximate the sphere's radius as 46 m near the ground.[18]
An object outside the critical distance is unlikely to be struck by the leader if there is a solidly grounded object within the critical distance. Locations that are considered safe from lightning can be determined by imagining a leader's potential paths as a sphere that travels from the cloud to the ground. For lightning protection, it suffices to consider all possible spheres as they touch potential strike points. To determine strike points, consider a sphere rolling over the terrain. At each point, we are simulating a potential leader position. Lightning is most likely to strike where 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 in most lightning diversion systems is in transporting the captured discharge from the lightning rod to the ground, though.[19] Lightning rods are typically installed around the perimeter of flat roofs, or along the peaks of sloped roofs at intervals of 6.1 m or 7.6 m, depending on the height of the rod.[20] When a flat roof has dimensions greater than 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 a rectangular grid pattern.[21]
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 its American colonies, British scientists maintained that a lightning rod should have a ball on its end. American scientists maintained that there should be a point. As of 2003[update], the controversy had not been completely resolved.[22] It is difficult to resolve the controversy because proper controlled experiments are nearly impossible in such work; in spite of the work of Moore, et al. [described below] most lightning rods seen on buildings have sharp points. Work performed by Charles B. Moore, et al.[23], in 2000 has helped this issue, finding that moderately rounded or blunt-tipped lightning rods act as marginally better strike receptors. [described below] As a result, round-tipped rods are installed the majority of the time on new systems in the United States. To quote:
- Calculations of the relative strengths of the electric fields above similarly exposed sharp and blunt rods show that while the fields are much stronger at the tip of a sharp rod prior to any emissions, they decrease more rapidly with distance. As a result, at a few centimeters above the tip of a 20-mm-diameter blunt rod, the strength of the field is greater 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 limited by the easy formation of ions in the surrounding air, the field strengths over blunt rods can be much stronger than those at distances greater than 1 cm over sharper ones.
- The results of this study suggest that moderately blunt metal rods (with tip height to tip radius of curvature ratios of about 680:1) are better lightning strike receptors than sharper rods or very blunt ones.
In addition, the height of the lightning protector relative to the structure to be protected and the Earth itself will have an effect.[24][25]
Dissipation & Charge Transfer Theories
A controversy over the assortment of operation theories dates back to the 18th century, when Franklin himself stated that 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.
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).[26][27] 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[28][29] and that a considerable electric current through the tower can be measured when thunderclouds are overhead.
Due to the large amounts of capital involved in lightning protection systems, dissipation-based lightning protection systems have been deemed "controversial". However, they have even been included in some national technical standards. Promoters of traditional Franklin systems claim they do not work, whereas multinational companies around the world use them to protect critical infrastructure and valuable commodities. Laboratory-scale measurements of the effects of dissipation devices do not scale to applications involving natural lighting. [30] However, full-scale systems are in operation protecting facilities at thousands of sites globally, even in the highest lightning strike prone areas of Central Africa Industrial Fire World, Vol. 22 No. 6.
Various investigators believe the natural downward lightning strokes to be unpreventable.[31] Dissipation or Charge Transfer proponents have never claimed to "prevent" lightning termination, rather they believe they can protect a site from direct termination by "relocating" the stroke termination to some location other than the protected facility by the reduction of the electrical potential between storm cell and facility.
The following 3 paragraphs represent vested interests in traditional "Franklin" lightning protection systems, and hence granted full immunity to publish whatever they want as they monitor this page, thereby promoting the "controversy".
Scientists from the National Lightning Safety Institute claim that these dissipation devices are nothing more than expensive lightning protectors and that they, unlike traditional methods, are not based on "scientifically proven and indisputable technical arguments".[32] William Rison states that in his opinion the underlying theory of dissipation is "scientific nonsense".[33]
According to these sources, there is no proof that the dissipation arrangement is at all effective. According to opponents of the dissipation technology, the various designs of 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 generation of upward lightning strokes.[31] Some field investigations of dissipaters show that their performance is comparable to conventional terminals and possess no great enhancement of protection. According to these field studies, these devices have not shown that they totally eliminated lightning strikes.[34]
No major standards body, such as the NFPA or UL, has currently endorsed a device that can prevent or reduce lightning strikes. The NFPA Standards Council, following a request for a project to address Dissipation Array Systems and Charge Transfer Systems, denied the request to begin forming standards on such technology (though the Council did not foreclose on future standards development after reliable sources demonstrating the validity of the basic technology and science were submitted).[35]
Early Streamer Emission (ESE) Theory
Initially, an NFPA independent third party panel stated that "the [Early Streamer Emission] lightning protection technology appears to be technically sound" and that there was an "adequate theoretical basis for the [Early Streamer Emission] air terminal concept and design from a physical viewpoint". (Bryan, 1999[36]) The same panel also concluded that "the recommended [NFPA 780 standard] lightning protection system has never been scientifically or technically validated and the Franklin rod air terminals have not been validated 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 of traditional 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.[37] The NFPA withdrew its proposed draft edition of standard 781 due to a lack of evidence of inceased effectiveness of Early Streamer Emission-based protection systems over conventional air terminals.
Since most lightning protectors' ground potentials are elevated, the path distance from the source to the elevated ground point will be shorter, creating a stronger field (measured in volts per unit distance) and that structure will be more prone to ionization and breakdown.[38]
Members of the Scientific Committee of the International Conference on Lightning Protection has issued a joint statement stating their opposition to Early Streamer Emission technology.[39]
Analysis of strikes
Lightning strikes to a metallic structure can vary from leaving no evidence excepting perhaps a small pit in the metal to the complete destruction of the structure (Rakov, Page 364).[40] When there is no evidence, analyzing the strikes is difficult. This means that a strike on an uninstrumented structure must be visually confirmed, and the random behavior of lightning renders such observations difficult.[40][41][42][43] There are also inventors working on this problem,[44][45] such as through a lightning rocket. While controlled experiments may be off in the future, very good data is being obtained through techniques which use radio receivers that watch for the characteristic electrical 'signature' of lightning strikes using fixed directional antennas.[46][47][48][49] Through accurate timing and triangulation techniques, lightning strikes can be located with great precision, so strikes on specific objects often can be confirmed with confidence.
The energy in a lightning strike is measured in joules. The reason that lightning does damage is that this energy is released in a matter of microseconds (typically 30 to 50 microseconds).
Standards
The introduction of lightning protection systems into standards allowed various manufactures to develop protector systems to a multitude of specifications. There are multiple international, national, corporate and military lightning protection standards.
- NFPA-780 Standard for the Installation of Lightning Protection Systems
- LPI-175 Standard of Practice for the Design - Installation - Inspection of Lightning Protection Systems
- M440.1-1, Electrical Storms and Lightning Protection, Department of Energy
- AFI 32-1065 - Grounding Systems, U. S. Air Force Space Command
- Motorola R-56 Standards and Guidance for Communications Sites
- FAA STD 019e, Lightning and Surge Protection, Grounding, Bonding and Shielding Requirements for Facilities and Electronic Equipment
- IEEE STD 142, Grounding of Industrial and Commercial Power Systems
- IEEE STD 1100, Powering and Grounding Electronic Equipment
- Lightning Protection Systems, UL's Lightning Protection program, Underwriters Laboratories
- IEC 62305 Series of lightning protection guidelines.
Aircraft protectors
Lightning protection for aircraft is provided by mounting devices on the aircraft structure. The protectors are provided with extensions through the structure of the aircraft's outer surface and within a static discharger. Protection systems for use in aircraft must protect critical and non-critical electronic equipment. Aircraft lightning protection provides an electrical path having a plurality of conductive segments, continuous or discontinuous, that upon exposure to a high voltage field form an ionization channel due to the system's breakdown voltage. Various lightning protection systems must reject the surge currents associated with the lightning strikes. Lightning protection means for aircraft include components which are dielectrics and metallic layers applied to the ordinarily lightning-accessible surfaces of composite structures. Various ground connection means to the layers comprises a section of wire mesh fusing the various layers to an attachment connecting the structure to an adjacent ground structure. Composite-to-metal or composite-to-composite structural joints are protected by making the interface areas conductive for transfer of lightning current.
Some aircraft lightning protection systems use a shielded cable system. These systems consist of one or more conductors enclosed by a conductive shield. The cable has both conductors of one end connected to a grounding element. This is intended to provide protection from electromagnetic interference. Such systems reduce the electromagnetically induced voltage in a shielded conductor. This is intended to provide protection against induced electromagnetic interference from lightning. This network provides a normally-high impedance which breaks down to a very low impedance in response to a momentary voltage surge electromagnetically induced in the shield. This establishes a conductive path between the shield and ground. Any surge voltage from lightning creates a current through the cable. This results in an electromagnetic field of the opposite direction, which cancels or reduces the magnitude of the electromagnetic field within the shielded cable.
Watercraft protectors
A lightning protection installation on a watercraft comprises a lightning protector mounted on the top of the mast or superstructure and a grounding conductor in contact with the water. Electrical conductors attach to the protector and run downward to the conductor. For a vessel with a conducting (iron or steel) hull, the grounding conductor is the hull. For a vessel with a non-conducting hull, the grounding conductor may be retractable, part of the hull, or attached to a centerboard.
See also
- List of lightning rod patents
- Grounding kit
- Václav Prokop Diviš (1698–1765), constructor of the first grounded lightning rod, in Přímětice u Znojma during 1750-1754.
- James Otis, Jr., contemporary of Ben Franklin, killed at doorway by lightning in Andover, Massachusetts on May 23, 1783.
Notes
- ^ Jernegan, M. W. (1928). "Benjamin Franklin's "Electrical Kite" and Lightning Rod". The New England Quarterly. 1 (2). The New England Quarterly: 180–196. doi:10.2307/359764. JSTOR 359764.
- ^ 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 Invention Independent?". Isis. 43 (4): 358–364. doi:10.1086/348160. ISSN 0021-1753. JSTOR 227389. - ^ I. Bernard Cohen, The Two Hundredth Anniversary of Benjamin Franklin's Two Lightning Experiments and the Introduction of the Lightning Rod, in: Proceedings of the American Philosophical Society, Vol. 96, No. 3. (Jun. 20, 1952), pp. 331–366.
- ^ The office of the first Russian oligarch Template:Ru icon
- ^ "History of Rebar". Whaley Steel.
- ^ Seckel, Al, and John Edwards, "Franklin's Unholy Lightning Rod". 1984.
- ^ Recovering Benjamin Franklin: an exploration of a life of science and service. Open Court Publishing. 1999. ISBN 9780812693874.
- ^ "Antique Lightning Rod Ball Hall of Fame". Antique Bottle Collectors Haven. (glass lightning balls collection)
- ^ 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.
- ^ Statue of Freedom http://www.aoc.gov/cc/art/freedom.cfm
- ^ The Point of a Monument: A History of the Aluminum Cap of the Washington Monument: The Functional Purpose
- ^ Sir William Thomson, Papers on Electrostatics and Magnetism.
- ^ a b U.S. Patent 1,266,175 – Tesla, "Lightning-Protector"
- ^ NFPA-780 Standard for the Installation of Lightning Protection Systems 2008 Edition - Annex B - B.4.3
- ^ NFPA-780 Standard for the Installation of Lightning Protection Systems 2008 Edition - Annex C
- ^ High-voltage surge eliminator, Roy B. Carpenter, Jr., U.S. patent 5,532,897. Page 1, Column 1, Line 26-27.
- ^ Donlon, Tim, "Lightning Protection for Historic Buildings". Cathedral Communications Limited, 2001.
- ^ Installation requirements for lightning protection systems - UL 96A 4.7.3.4.2
- ^ Lightning protection installation, U.S. patent 3,919,956
- ^ Installation requirements for lightning protection systems - UL 96A 8.2.2
- ^ Standard for the installation of lightning protection systems 2008 edition - NFPA-780 4.8.2.4
- ^ Ian Godwin (March 26, 2003). "Franklin letter to King fans flames of lightning debate". ABC Science Online. Australian Broadcasting Corporation. Retrieved July 29, 2011.
- ^ C. B. Moore, William Rison, James Mathis, and Graydon Aulich, "Lightning Rod Improvement Studies". 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.
- ^ U.S. patent 1,266,175, Tesla, "Lightning-Protector".
- ^ U.S. patent 3,371,144, Griscom, "Transmission-line lightning-proofing structures". Page 25, Column 5. (cf. [...] the charge on a leader as a function of height above ground[...])
- ^ U.S. patent 6,307,149, Richard Ralph Zini, et al., Non-contaminating lightning protection system. Claim one and claim ten.
- ^ John Richard Gumley, U.S. patent 6,320,119, Lightning air terminals and method of design and application
- ^ Emitter of ions for a lightning rod with a parabolic reflector, Manuel Domingo Varela, U.S. patent 6,069,314.
- ^ Lightning-protector for electrical conductors, Johathan H. Vail, U.S. patent 357,050.
- ^ Vernon Cooray (ed.) Lightning Protection, The Institution of Engineering and Technology, 2010, ISBN 978-1-84919-106-7 pp. 240-260, p 320
- ^ a b Mousa, Abdul M. "The applicability of Lightning Elimination Devices to Substations and Power Lines". British Columbia Hydro, Burnaby, British Columbia, Canada V3N 4X8.
- ^ Mousa, Abdul M. (1999). "Scientists Oppose Early Streamer Air Terminals". National Lightning Safety Institute. Retrieved 2006-09-18.
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- ^ Rison, William (2001). "There Is No Magic To Lightning Protection: Charge Transfer Systems Do Not Prevent Lightning Strikes" (pdf). National Lightning Safety Institute. Retrieved 2006-09-18.
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- ^ Rison, W., Moore, C.B., and Aulich, G.D., "Lightning air terminals - is shape important?", Electromagnetic Compatibility, 2004. EMC 2004. 2004 InternationalSymposium on Volume 1, 9–13 August 2004 Page(s):300 - 305 vol.1
- ^ Casey C. Grant, "To: Interested Parties"
- ^ Bryan, R. G., et al., "Report of the Third-Party Independent Evaluation Panel on the Early Streamer Emission Lightning Protection Technology".
- ^ Report of The Committee on Atmospheric And Space Electricity of The American Geophysical Union on The Scientific Basis for Traditional Lightning Protection Systems
- ^ U.S. patent 1,869,661, Bumbraugh, "Lightning protection system and method".
- ^ Mousa, Abdul M. "Scientists Oppose Early Streamer Air Terminals", 1999.
- ^ a b Rakov, et al., Lightning: physics and effects
- ^ Martin A. Uman, Lightning Discharge. Courier Dover Publications, 2001. 377 pages. ISBN 0486414639
- ^ Donald R. MacGorman, The Electrical Nature of Storms. Oxford University Press (US), 1998. 432 pages. ISBN 0195073371
- ^ Hans Volland, Handbook of Atmospheric Electrodynamics, Volume I. CRC Press, 1995. 408 pages. ISBN 0849386470
- ^ Method and apparatus for the artificial triggering of lightning, Douglas A. Palmer, U.S. patent 6,012,330
- ^ Lightning rocket, Robert E. Betts, U.S. patent 6,597,559
- ^ Lightning locating system, Ralph J. Markson et al., U.S. patent 6,246,367.
- ^ Lightning locating system, Airborne Research Associates, Inc., U.S. patent 5,771,020.
- ^ 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 6,420,862
- ^ 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 6,552,521.
References
- Vladimir A. Rakov and Martin A. Uman, Lightning: physics and effects. Cambridge University Press, 2003. 698 pages. ISBN 0521583276
- J. L. Bryan, R. G. Biermann and G. A. Erickson, "Report of the Third-Party Independent Evaluation Panel on the Early 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 to C. 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", Bulletin of the American Meteorological Society, December 2002.
- Mousa, Abdul M. "War of the Lightning Rods", Electricity Today, 2004.
- Zipse, Donald. "Prevent Lightning Strikes with Charge Transfer Systems", Power Quality, November 2001
- Zipse, Donald. "Lightning protection methods: An update and a discredited system vindicated", IEEE Trans. on Industry Applications, 37, 407-414, 2001.
- Carpenter, Jr., Roy B. "Preventing Direct Strikes".
External links
- "Researchers find that blunt lightning rods work best". 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". National Transportation Library, 2002-08-09.
- Kithil, Richard, "Lightning Rods: Recent Investigations". National Lightning Safety Institute, September 26, 2005.
- Kithil, Richard, "Should Lightning Rods be Installed?". National Lightning Safety Institute, September 26, 2005.
- Kithil, Richard, "Fundamentals of Lightning Protection". National Lightning Safety Institute, September 26, 2005.
- Nailen, Richard L., "Lightning controversy goes on", The Electrical Apparatus, February 2001.
- Lightning Safety Alliance education 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 W.S. Orr 1855.
- February 1919 Popular Science article about Lightning Arresters and how they were used in early AC and DC power distribution systems, Electrical Devices and How They Work, Part 14: Lightning Arresters, Popular Science monthly, February 1919, 5 unnumbered pages, Scanned by Google Books: http://books.google.com/books?id=7igDAAAAMBAJ&pg=PT17