NFPA 780H-2014 Standard for the Installation of Lightning Protection Systems Handbook.pdf

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1、NFPA780Standard for the Installation of Lightning Protection SystemsHandbook 2014780NFPA, 1 Batterymarch Park, Quincy, MA 02169-7471, USAAn International Codes and Standards OrganizationNFPA, 1 Batterymarch Park, Quincy, MA 02169-7471An International Codes and Standards OrganizationNFPA780Standard f

2、or the Installation ofLightning Protection SystemsHandbook 2014Second EditionAnnotated by Richard RouxCopyright 2014National Fire Protection AssociationOne Batterymarch Park Quincy, Massachusetts 02169-7471All rights reserved. About this Handbook EditionThis PDF contains the complete 2014 edition of

3、 NFPA 780, Standard for the Installation of Light-ning Protection Systems, annotated to assist the readers understanding of the standards language and the intent behind it. The annotations are not part of the NFPA Standard but provide a valu-able commentary reflecting the views, explanations, and in

4、sights of authors and contributors selected by the NFPA based on their knowledge of and experience with the standard.How to Navigate Between the Text of the Standard and the AnnotationsNavigate between code or standard text and annotations by using hyperlinked icons and code numbers. While in code o

5、r standard text, click on hyperlinked s icon* to the left of the standard sec-tion to navigate to corresponding annotations. Click on the hyperlinked annotative standard section number 1.1 to return to previous standard section.*Please note, only the sections featuring icons contain annotations.For

6、longer blocks of annotations, it is recommended that you enable the back arrow functional-ity in Acrobats page navigation menu, which will also allow you to return to the previous stan-dard section.How to Ensure You Have the Most Up-to-date Version of the NFPA StandardThe NFPA Standard, in the editi

7、on contained herein, is current as of the effective date des-ignated at the time the standard was issued 2014. This Handbook Edition does not, however, include errata, tentative interim amendments (TIAs), or formal interpretations (FIs) that may have been issued after the effective date. For all err

8、ata, TIAs, or FIs that may have been issued since the effective date, or for any new editions that may have superseded this edition, please visit the “Document Information pages” link for the relevant NFPA Standard located in the “Codes email: stds_adminnfpa.org.For more information about NFPA, visi

9、t the NFPA website at www.nfpa.org. IMPORTANT NOTICES AND DISCLAIMERS CONCERNING THE HANDBOOk EDITIONNotice and Disclaimer Concerning LiabilityPublication of this Handbook Edition is for the purpose of circulating information and opinion among those concerned for fire and electrical safety and relat

10、ed subjects. While every effort has been made to achieve a work of high quality, neither the NFPAnor the contributors to this Handbook Edition guarantee the accuracy or completeness of or assume any liability in connec-tion with the information and opinions contained in this Handbook Edition. The NF

11、PA and the contributors shall in no event be liable for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, or reliance upon this Handbook Edition.This Hand

12、book Edition is published with the understanding that the NFPA and the contribu-tors to this Handbook Edition are supplying information and opinion but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professiona

13、l should be sought.NFPA codes, standards, recommended practices, and guides (“NFPA Standards”), includ-ing the NFPA Standard that is the subject of this Handbook Edition, are made available for use subject to Important Notices and Disclaimers Concerning NFPA Standards, which are separately bookmarke

14、d and viewable in this Handbook Edition, and which can also be viewed at www.nfpa.org/disclaimers.Notice Concerning Interpretations Contained in the AnnotationsNFPA codes, standards, recommended practices, and guides (“NFPA Standards”), including the NFPA Standard that is the subject of this Handboo

15、k Edition are developed in accordance with the published procedures of the NFPA by technical committees comprised of volunteers drawn from a broad array of relevant interests. In this Handbook Edition the text of the NFPA Standard is accompanied with annotations providing explanation and commentary

16、on the meaning and intent of the Standard. The annotations contained in this Handbook Edition are not a part of the NFPA Standard and do not constitute Formal Interpretations of the NFPA (which can be obtained only through requests processed by the responsible technical committees in accordance with

17、 the published procedures of the NFPA). The annotations, therefore, solely reflect the personal opinions of the author or other contributors and do not necessarily represent the official position of the NFPA or its technical committees.ISBN: 978-1455910090Copyright 2013 National Fire Protection Asso

18、ciation. All Rights Reserved.NFPA780Standard for theInstallation of Lightning Protection Systems2014 EditionThis edition of NFPA 780, StandardfortheInstallationofLightningProtectionSystems, was preparedby the Technical Committee on Lightning Protection. It was issued by the Standards Council onMay 2

19、8, 2013, with an effective date of June 17, 2013, and supersedes all previous editions.This edition of NFPA 780 was approved as an American National Standard on June 17, 2013.Origin and Development of NFPA 780NFPA first adopted Specifications for Protection of Buildings Against Lightning in 1904. Re

20、visedstandards were adopted in 1905, 1906, 1925, 1932, and 1937. In 1945, the NFPA Committee andthe parallel American Standards Association (ASA) Committee on Protection Against Lightningwere reorganized and combined under the sponsorship of NFPA, the National Bureau of Stan-dards, and the American

21、Institute of Electrical Engineers (now the IEEE). In 1946, NFPA acted toadopt Part III and in 1947 published a revised edition incorporating this part. Further revisionsrecommended by the Committee were adopted by NFPA in 1949, 1950, 1951, 1952, 1957, 1959,1963, 1965, 1968, 1975, 1977, 1980, 1983, 1

22、986, 1989, and 1992.Commencing with the 1992 edition of the Lightning Protection Code, the NFPA numericaldesignation of the document was changed from NFPA 78 to NFPA 780.With the issuance of the 1995 edition, the name of the document was changed fromLightning Protection Code to Standard for the Inst

23、allation of Lightning Protection Systems. Thischange was directed by the Standards Council in order to make the title more accuratelyreflect the documents content. In addition, the Council directed certain changes to thescope of the document to clarify that the document did not cover lightning prote

24、ction instal-lation requirements for early streamer emission systems or lightning dissipater array systems.The 1997 edition of NFPA 780 incorporated editorial changes to make the documentmore user friendly.In issuing this document, the Standards Council noted that lightning is a stochastic, if notca

25、pricious, natural process. Its behavior is not yet completely understood. This standard isintended to provide requirements, within the limits of the current state of knowledge, for theinstallation of those lightning protection systems covered by the standard.The 2000 edition of NFPA 780 was amended

26、to provide requirements for open structuressuch as those found on golf courses. A 1998 lightning flash density chart replaced the 1972lightning frequency isoceraunic chart.The 2004 edition of NFPA 780 reflected an extensive editorial revision of the standard tocomply with the concurrent edition of t

27、he NFPA Manual of Style for Technical Committee Docu-ments. These revisions included the addition of three administrative chapters at the beginningof the standard: “Administration,” “Referenced Publications,” and “Definitions.” Five techni-cal chapters followed the administrative chapters in the sam

28、e sequence as in the 2000 edition.Other editorial revisions included the breakout of paragraphs with multiple requirementsinto an individually numbered paragraph for each requirement, the minimization of the useof exceptions, the use of consistent headings for sections and section subdivisions, and

29、reor-ganization to limit paragraph numbering to six digits. The International System of Units,commonly known as SI or metric, was used throughout the document. The appendixes wererenamed annexes and reordered in a more logical sequence.The 2004 edition also contained a number of technical revisions

30、throughout the standard.These revisions included the following: a main conductor, solid strip, was added for Class IImaterial requirements for ordinary structures exceeding 75 ft in height; handrails could beused as a substitute for down conductors; additional separation between ground rods wasrequi

31、red where multiple ground rods are used; additional guidance was provided for those7801NFPA and National Fire Protection Association are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts 02169.instances where it is necessary to install the grounding conductor d

32、irectly on bedrock; the section entitled SurgeSuppression was entirely rewritten; titanium strike termination devices were permitted to be used; and in Annex K theterm Faraday cage was replaced with metallic cage.The 2008 edition provided requirements for surge protective devices to be installed at

33、all power service entrances,at the entrance of conductive communications systems and antenna systems, and where an electrical or electronicsystem conductor leaves the structure.The new definition for lightning protection system included the term conductive structural members. Clarification wasprovid

34、ed relative to the use of ancillary metal parts that cannot be substituted for the main conductor. Strike termina-tion devices included air terminals, metal masts, certain permanent metal parts of structures, and elevated conductors.Revisions clarified that metal masts and overhead ground wires were

35、 included in the requirements of Chapter 4.Significant changes were made to the requirements for the use of bimetallic clamps and aluminum in proximity toearth. The standard has long required that grounding electrodes be located near the outside perimeter of the struc-ture, and in the 2008 edition a

36、dditional guidance was provided to assist the system designer. Changes were also madeto better address the requirements for grounding electrodes in shallow topsoil applications.The requirements for the use of multiple ground rods were revised. Revisions were also made in numerous areas ofthe standar

37、d for clarity and to enhance its usability. Revisions to the graphs and formulas for the rolling sphere methodwere made to facilitate their use in metric units.Requirements were added to address proper installation of lightning protection equipment on large roof top mechani-cal units. The installati

38、on of air terminals and main-size conductors in these applications were quantified and detailed.Revisions were made to enhance and clarify the requirements for the bonding together of all grounded media andunderground metallic piping. The intent was to provide for potential equalization and not to u

39、se the metallic piping asa lightning protection system grounding electrode. All grounding media and buried metallic conductors that mightassist in providing a path for lightning currents in or on a structure must be interconnected to provide a commonground potential. Guidance was provided on the use

40、 of isolating spark gaps.Significant changes were made to the requirements pertaining to the conductors and other lightning protectionsystem hardware used near the top of a heavy-duty stack.Other significant changes included a complete rewrite of Chapter 8, Protection for Watercraft, providing a num

41、berof technical revisions; more user information added in Annex B, Principles of Lightning Protection; and a revision ofAnnex F, Protection for Trees.In addition to significant technical changes, the 2011 edition included new and revised text.With the addition of two new chapters, the 2011 edition o

42、f the standard presented a major change in the scope ofthe document. The first new chapter addressed the protection of structures housing ammunition and explosivematerials. The second new chapter included requirements for providing lightning protection for wind turbines,specifically wind turbine str

43、uctures that comprise externally rotating blades, a nacelle, and a supporting tower. The2011 edition was substantially reorganized to accommodate these new chapters in a logical order.The sections pertaining to strike termination devices, zones of protection, and the rolling sphere method weretotall

44、y reorganized for better usability. The text clearly provided that strike termination devices include air terminals,metal masts, permanent metal parts of structures, and overhead ground wires. The text qualified where a metal mastwould be permitted to serve as the down conductor. The requirements fo

45、r overhead ground wires and masts andoverhead ground wires were relocated.The 2011 edition clarified the requirements for strike termination devices at the eaves for a pitched roof, and afigure was added to graphically illustrate that condition.A new section on roof top helipads provided requirement

46、s to ensure that an adequate level of protection isprovided to those areas within the height and safety criteria set forth by the Federal Aviation Administration (FAA) orother AHJs.Chapter 7 provided requirements for the protection of structures containing flammable vapors, flammable gases,or liquid

47、s that can give off flammable vapors. The section on floating roof tanks was revised in its entirety as a result ofrecent testing and research conducted for aboveground storage tanks.The lightning risk assessment methodology provided in Annex L was completely rewritten. The lightning riskassessment

48、was provided to assist the building owner, safety professional, or architect/engineer in determining the riskof damage or injury due to lightning. This annex provided both a simplified, quick-look assessment and a moredetailed assessment for those requiring a more detailed analysis. Once the level o

49、f risk has been determined, thedevelopment of appropriate lightning protection measures can begin.The 2014 edition provides reorganization of Sections 4.7 and 4.8, to better align the requirements for strike terminationdevices. Reorganization of these sections in a more logical order clarifies the requirements and application of the standard.Previously, these requirements were intermingled, causing confusion and possible misapplication. Section 4.8 has also beenrevised to clarify the requirements for protection where small objects are located on roofs.Section 4.14 has bee