BS 6651:1999:2005 Edition
$215.11
Code of practice for protection of structures against lightning
| Published By | Publication Date | Number of Pages |
| BSI | 2005 | 112 |
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 1 | BRITISH STANDARD |
| 2 | Committees responsible for this British�Standard |
| 3 | Contents |
| 9 | Introduction 1 Scope 2 Normative references |
| 10 | 3 Definitions and abbreviations 3.1 Definitions |
| 13 | 3.2 Abbreviations 4 Technical aspects of lightning 4.1 General 4.2 Characteristics of lightning |
| 14 | Figure 1 Lightning flash density to ground |
| 15 | 5 Effects of lightning strike 5.1 Electrical effects 5.2 Side-flashing |
| 16 | 5.3 Thermal effects 5.4 Mechanical effects 6 Function of a lightning conductor Table 1 Recommended fixing centres for conductors |
| 17 | 7 Materials |
| 18 | Figure 2 Typical designs for lightning conductor fixings |
| 19 | 8 Dimensions Table 5 Minimum thicknesses of sheet metal used for roofing and forming part of the air termination network 9 Basic considerations 10 Need for protection 10.1 General |
| 20 | 10.2 Estimation of exposure risk Table 6 Relationship between thunderstorm days per year and lightning flashes per square kilometre per year |
| 21 | 10.3 Risks associated with everyday living 10.4 Suggested acceptable risk 10.5 Overall assessment of risk 10.6 Weighting factors |
| 22 | Figure 3 Map showing thunderstorm days per year throughout the world |
| 23 | Table 7 Comparative�probability�of�death�for�an�individual�per�year�of�exposure (order�of�magnitude�only) Table 8 Weighting factor Table 9 Weighting factor |
| 24 | Table 10 Weighting factor Table 11 Weighting factor Table 12 Weighting factor 10.7 Interpretation of overall risk factor |
| 25 | 10.8 Sample calculation of overall risk factor 11 Zone of protection 11.1 General |
| 26 | 11.2 Protective angle 11.3 Structures of exceptional vulnerability |
| 27 | Table 13 Examples of calculations for evaluating the need for protection |
| 29 | Figure 4 Details of structures and collection areas |
| 31 | Figure 5 Examples of lightning protection systems for brick chimneys |
| 32 | Figure 6 Protective angles and zones of protection for various forms of air termination |
| 33 | 12 General considerations for system design 13 Consultation 13.1 General 13.2 Architect 13.3 Public utilities |
| 34 | 13.4 Fire and safety officers 13.5 Television and radio installers 13.6 Builder |
| 35 | 14 Component parts 15 Air terminations 15.1 General 15.2 Basic rules |
| 36 | Figure 7 Examples of air terminations and down conductors using handrails, metal copings and reinforcing bars |
| 37 | Figure 8 Test joints |
| 38 | Figure 9 Typical forms of vertical air terminations |
| 39 | Figure 10 Air terminations for a flat roof |
| 40 | Figure 11 Air terminations for flat roofs at different levels |
| 41 | Figure 12 Air terminations for large areas of roof of various profiles |
| 42 | Figure 13 Air terminations and concealed conductors for buildings less than 20 m high with sloping roofs |
| 43 | Figure 14 Air terminations and down conductors for flat roof buildings |
| 44 | Figure 15 Air terminations for tall conducting structures |
| 45 | Figure 16 Air termination network with horizontal conductors for a structure with explosive or highly flamm… |
| 46 | Figure 17 Air termination for a flat roof showing connection to a standing seam joint when a metallic roof … 15.3 Forms of air termination |
| 48 | 16 Down conductors 16.1 General |
| 49 | Figure 18 Air termination and zone of protection for simple structure with explosive or highly flammable co… |
| 50 | 16.2 Pattern of down conductors 16.3 Recommended number 16.4 Tall structures presenting inspection difficulties 16.5 Routeing 16.6 Use of reinforcement in concrete structures |
| 52 | Figure 19 Patterns of down conductors (natural or not) for various forms of tall building |
| 53 | Figure 20 Voltage gradients along ground surface near to masts, towers and columns with single multiple ear… |
| 54 | 16.7 Internal routes 16.8 Sharp bends and re-entrant loops 16.9 Bonding to prevent side-flashing |
| 55 | Figure 21 Down conductor in internal duct Figure 22 Re-entrant loops |
| 56 | 16.10 Bonds |
| 57 | 16.11 Test points 17 Earth termination network 17.1 Resistance to earth |
| 58 | 17.2 Importance of reducing resistance to earth 17.3 Common network for all services 17.4 Isolation of earth electrode systems for testing 17.5 Structures on rock 18 Earth electrodes 18.1 General 18.2 Ground conditions 18.3 Earth rods |
| 59 | Figure 23 Lightning protection system for tall buildings (over 20 m high) showing air terminations, down co… |
| 60 | 18.4 Strips 19 Metal in or on a structure 19.1 General 19.2 Isolation |
| 61 | Figure 24 Example of an earth electrode seal for use within a tanked structure |
| 62 | Figure 25 Earth terminations: arrangement of earth electrodes |
| 63 | Figure 26 Curve for determining the probable maximum current in the lightning flash from the ratio |
| 64 | Figure 27 Transfer inductance in simple loop |
| 67 | 19.3 Conditions where bonding is needed |
| 68 | Figure 28 Curve for determination of the flashover voltage as a function of spacing |
| 69 | Figure 29 Plan of collection area |
| 70 | Figure 30 Diagram showing bonding to services (gas, water and electricity) 20 Structures exceeding 20 m in height 20.1 Non-conducting structures 20.2 Conducting structures |
| 71 | 20.3 All types of stayed structure 20.4 Church towers and spires 21 Structures with roofs of high flammability 21.1 Air terminations 21.2 Conductors and bonds 22 Buildings with explosive or highly flammable contents 22.1 General |
| 72 | 22.2 Protective methods |
| 73 | Figure 31 Church towers and spires |
| 74 | Figure 32 Air termination with twin suspended horizontal conductors and zone of protection for structures w… |
| 75 | Figure 33 Vertical air termination for protection of explosive stores |
| 77 | 23 Dwelling houses 24 Fences 24.1 Nature of danger |
| 78 | Figure 34 Exceptional protection against overvoltages induced by lightning in incoming supplies to building… |
| 79 | Figure 35 Lightning protection for domestic properties |
| 80 | 24.2 Protection of livestock in fields 24.3 Fences surrounding structures containing flammable liquids or gases 25 Trees and structures near trees |
| 81 | 26 Structures with radio and television aerials 26.1 Indoor aerials in protected structures 26.2 Outdoor aerials in protected structures 26.3 Aerials on unprotected structures 26.4 Use of earth electrodes of lightning protection system |
| 82 | 27 Miscellaneous structures 27.1 Tents and marquees 27.2 Metal scaffolding and similar structures 27.3 Tall metal masts, tower cranes and revolving and travelling structures 27.4 Low cost buildings in areas of high lightning incidence |
| 83 | Figure 36 Lightning protection for tents 27.5 Sports stadiums |
| 84 | 27.6 Windmills Figure 37 Lightning protection (low cost installation) for isolated farm buildings of brick and tile constr… |
| 85 | Figure 38 Lightning protection system for sports stadium (football ground) |
| 86 | 27.7 Bridges 28 Corrosion 28.1 General |
| 87 | 28.2 Electrolytic corrosion between dissimilar metals 28.3 Chemical corrosion of aluminium near Portland cement, mortar mixes, etc. |
| 88 | Figure 39 Typical arrangement for protection of windmills |
| 89 | Figure 40 Bridges |
| 90 | 28.4 Chemical corrosion of copper 29 Structures 30 Overhead power lines 31 Inspection 32 Testing |
| 91 | 33 Records 34 Maintenance and upkeep |
| 92 | Annex A (informative) Explanatory notes on some of the recommendations of this code A.1 Earth termination network earth electrodes |
| 93 | Table A.1 Relationship between diameter and mass of electrodes |
| 94 | A.2 Metal in or on a structure and structures exceeding 20�m in height |
| 95 | A.3 Trees and structures near trees A.4 Miscellaneous structures |
| 96 | A.5 Structures with complex geometry |
| 97 | Figure A.1 Examples of use of the “rolling sphere method” for assessing a tall complex building for regions … |
| 98 | Annex B (informative) Guidance on the application of BS 6651 B.1 “Zone of protection” and “rolling sphere” methods of lightning protection B.2 Damage to metal cladding caused by direct arc-connected strike B.3 Tall brick-built chimneys B.4 Lightning protection for flat roofs |
| 99 | B.5 Air terminations and tiled roofs B.6 Design of a lightning protection system for a structure having different side elevation heights e… B.7 Use of reinforcement in concrete structures |
| 100 | B.8 Lightning protection system for a reinforced concrete chimney B.9 Down conductors in internal ducts B.10 Recommendations for lift installations |
| 101 | B.11 Earthing of steel framed buildings B.12 Bonding of external metal clad structures B.13 Bonding of the lightning conductor to the main earthing terminal |
| 102 | B.14 Bonding of the lightning conductor to service pipes B.15 Utilizing steelwork beneath combustible roofing materials as an air termination Annex C (informative) General advice on protection against lightning of electronic equipment within or on… C.1 General |
| 103 | C.2 Application of this annex Figure C.1 Strike location points to industrial installations which could affect electronic systems |
| 104 | C.3 Basic considerations of electronic system lightning protection C.3.1 Exposure levels C.3.2 Protection provided by the building |
| 105 | Figure C.2 Configurations involving electronic equipment Figure C.3 Lightning current distribution in a fifteen stanchion building |
| 106 | Figure C.4 Plan view of fifteen stanchion building showing resulting field line plot (transfer�inductance co… |
| 107 | C.4 Risk assessment C.4.1 Decision to install lightning protection |
| 108 | C.4.2 The probable number of lightning strikes Table C.1 Effective collection area of mains services |
| 109 | Table C.2 Effective collection area of data lines C.4.3 Vulnerability of the system configuration Table C.3 Weighting factor |
| 110 | Table C.4 Weighting factor Table C.5 Weighting factor C.4.4 Risk of a lightning strike to a particular system configuration C.5 Decision to provide protection Table C.6 Classification of structures and contents |
| 111 | Table C.7 Classification of exposure level C.6 Sample calculations |
| 115 | Figure C.5 Collection area of structure and adjacent associated structure C.7 Methods of protection of installations against lightning C.7.1 Earthing, bonding and potential equalization |
| 117 | Figure C.6 Cables entering a building separated from a transmitter mast |
| 118 | Figure C.7 Bonding of cables and pipes at entry and exit to buildings |
| 119 | C.7.2 Location of electronic equipment and cables C.7.3 Protection of building-to-building data lines |
| 120 | Figure C.8 Methods of reducing induced voltages |
| 121 | Figure C.9 Hybrid earth system applied to equipment in multi-floor building |
| 122 | Figure C.10 Earth connection from zero voltage reference of equipment to earth of surge protection devices C.7.4 Protection of equipment having component parts on the outside of buildings or connected to towers… |
| 123 | C.8 Characteristics and effects of lightning C.8.1 Additional characteristics of lightning relevant to electronic equipment C.8.2 Strike points for lightning |
| 124 | Figure C.11 Direct injection into exposed electrical system Figure C.12 Protection from direct injection |
| 125 | Figure C.13 Protection of cables located alongside tall vessels and bonding at roof level |
| 126 | Figure C.14 Locations where high, medium or low lightning current can be expected to flow through cables asso… Figure C.15 Lightning current characteristics for severe negative strike |
| 127 | Figure C.16 Strike points on plant |
| 128 | C.9 Lightning-induced transients and protection principles |
| 130 | C.10 Sample calculations of induced voltage in instrumentation loops C.11 Sample calculation for protection of inner core(s) of coaxial cable |
| 131 | C.12 Sample calculation of induced voltage in wiring |
| 132 | C.13 Surge protection devices, location categories and testing C.13.1 Location categories C.13.2 Magnitude of representative wave forms for testing mains surge protection devices Table C.8 Location category A (mains) |
| 133 | Table C.9 Location category B (mains) Table C.10 Location category C (mains) C.13.3 Testing mains surge protection devices C.13.4 Magnitude of representative waveform for testing data line barriers Table C.11 Location category C (data lines) C.13.5 Testing data line surge protection devices C.13.6 Information to be provided by manufacturers of surge protection devices |
| 134 | C.13.7 Combination wave test generator |
| 135 | Table C.12 Definitions of the waveshape parameters 1.2/50 4s Figure C.17 Inductance |
| 136 | Figure C.18 Simplified circuit diagram of the combination wave generator Figure C.19 Waveshape of open circuit voltage |
| 137 | Figure C.20 Waveshape of short circuit current |
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