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BS 6651:1999 Code of practice for protection of structures against lightning, 2005
- BRITISH STANDARD [Go to Page]
- Committees responsible for this British�Standard
- Contents
- Introduction [Go to Page]
- 1 Scope
- 2 Normative references
- 3 Definitions and abbreviations [Go to Page]
- 3.1 Definitions
- 3.2 Abbreviations
- 4 Technical aspects of lightning [Go to Page]
- 4.1 General
- 4.2 Characteristics of lightning [Go to Page]
- Figure 1 Lightning flash density to ground
- 5 Effects of lightning strike [Go to Page]
- 5.1 Electrical effects
- 5.2 Side-flashing
- 5.3 Thermal effects
- 5.4 Mechanical effects
- 6 Function of a lightning conductor [Go to Page]
- Table 1 Recommended fixing centres for conductors
- 7 Materials [Go to Page]
- Figure 2 Typical designs for lightning conductor fixings
- 8 Dimensions [Go to Page]
- 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 [Go to Page]
- 10.1 General
- 10.2 Estimation of exposure risk [Go to Page]
- Table 6 Relationship between thunderstorm days per year and lightning flashes per square kilometre per year
- 10.3 Risks associated with everyday living
- 10.4 Suggested acceptable risk
- 10.5 Overall assessment of risk
- 10.6 Weighting factors [Go to Page]
- Figure 3 Map showing thunderstorm days per year throughout the world
- 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
- Table 10 Weighting factor
- Table 11 Weighting factor
- Table 12 Weighting factor
- 10.7 Interpretation of overall risk factor
- 10.8 Sample calculation of overall risk factor
- 11 Zone of protection [Go to Page]
- 11.1 General
- 11.2 Protective angle
- 11.3 Structures of exceptional vulnerability [Go to Page]
- Table 13 Examples of calculations for evaluating the need for protection [Go to Page]
- Figure 4 Details of structures and collection areas
- Figure 5 Examples of lightning protection systems for brick chimneys
- Figure 6 Protective angles and zones of protection for various forms of air termination
- 12 General considerations for system design
- 13 Consultation [Go to Page]
- 13.1 General
- 13.2 Architect
- 13.3 Public utilities
- 13.4 Fire and safety officers
- 13.5 Television and radio installers
- 13.6 Builder
- 14 Component parts
- 15 Air terminations [Go to Page]
- 15.1 General
- 15.2 Basic rules [Go to Page]
- Figure 7 Examples of air terminations and down conductors using handrails, metal copings and reinforcing bars
- Figure 8 Test joints
- Figure 9 Typical forms of vertical air terminations
- Figure 10 Air terminations for a flat roof
- Figure 11 Air terminations for flat roofs at different levels
- Figure 12 Air terminations for large areas of roof of various profiles
- Figure 13 Air terminations and concealed conductors for buildings less than 20 m high with sloping roofs
- Figure 14 Air terminations and down conductors for flat roof buildings
- Figure 15 Air terminations for tall conducting structures
- Figure 16 Air termination network with horizontal conductors for a structure with explosive or highly flamm...
- 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
- 16 Down conductors [Go to Page]
- 16.1 General [Go to Page]
- Figure 18 Air termination and zone of protection for simple structure with explosive or highly flammable co...
- 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 [Go to Page]
- Figure 19 Patterns of down conductors (natural or not) for various forms of tall building
- Figure 20 Voltage gradients along ground surface near to masts, towers and columns with single multiple ear...
- 16.7 Internal routes
- 16.8 Sharp bends and re-entrant loops
- 16.9 Bonding to prevent side-flashing [Go to Page]
- Figure 21 Down conductor in internal duct
- Figure 22 Re-entrant loops
- 16.10 Bonds
- 16.11 Test points
- 17 Earth termination network [Go to Page]
- 17.1 Resistance to earth
- 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 [Go to Page]
- 18.1 General
- 18.2 Ground conditions
- 18.3 Earth rods [Go to Page]
- Figure 23 Lightning protection system for tall buildings (over 20 m high) showing air terminations, down co...
- 18.4 Strips
- 19 Metal in or on a structure [Go to Page]
- 19.1 General
- 19.2 Isolation [Go to Page]
- Figure 24 Example of an earth electrode seal for use within a tanked structure
- Figure 25 Earth terminations: arrangement of earth electrodes
- Figure 26 Curve for determining the probable maximum current in the lightning flash from the ratio
- Figure 27 Transfer inductance in simple loop
- 19.3 Conditions where bonding is needed [Go to Page]
- Figure 28 Curve for determination of the flashover voltage as a function of spacing
- Figure 29 Plan of collection area
- Figure 30 Diagram showing bonding to services (gas, water and electricity)
- 20 Structures exceeding 20 m in height [Go to Page]
- 20.1 Non-conducting structures
- 20.2 Conducting structures
- 20.3 All types of stayed structure
- 20.4 Church towers and spires
- 21 Structures with roofs of high flammability [Go to Page]
- 21.1 Air terminations
- 21.2 Conductors and bonds
- 22 Buildings with explosive or highly flammable contents [Go to Page]
- 22.1 General
- 22.2 Protective methods [Go to Page]
- Figure 31 Church towers and spires
- Figure 32 Air termination with twin suspended horizontal conductors and zone of protection for structures w...
- Figure 33 Vertical air termination for protection of explosive stores
- 23 Dwelling houses
- 24 Fences [Go to Page]
- 24.1 Nature of danger [Go to Page]
- Figure 34 Exceptional protection against overvoltages induced by lightning in incoming supplies to building...
- Figure 35 Lightning protection for domestic properties
- 24.2 Protection of livestock in fields
- 24.3 Fences surrounding structures containing flammable liquids or gases
- 25 Trees and structures near trees
- 26 Structures with radio and television aerials [Go to Page]
- 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
- 27 Miscellaneous structures [Go to Page]
- 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 [Go to Page]
- Figure 36 Lightning protection for tents
- 27.5 Sports stadiums
- 27.6 Windmills [Go to Page]
- Figure 37 Lightning protection (low cost installation) for isolated farm buildings of brick and tile constr...
- Figure 38 Lightning protection system for sports stadium (football ground)
- 27.7 Bridges
- 28 Corrosion [Go to Page]
- 28.1 General
- 28.2 Electrolytic corrosion between dissimilar metals
- 28.3 Chemical corrosion of aluminium near Portland cement, mortar mixes, etc. [Go to Page]
- Figure 39 Typical arrangement for protection of windmills
- Figure 40 Bridges
- 28.4 Chemical corrosion of copper
- 29 Structures
- 30 Overhead power lines
- 31 Inspection
- 32 Testing
- 33 Records
- 34 Maintenance and upkeep
- Annex A (informative) Explanatory notes on some of the recommendations of this code [Go to Page]
- A.1 Earth termination network earth electrodes [Go to Page]
- Table A.1 Relationship between diameter and mass of electrodes
- A.2 Metal in or on a structure and structures exceeding 20�m in height
- A.3 Trees and structures near trees
- A.4 Miscellaneous structures
- A.5 Structures with complex geometry [Go to Page]
- Figure A.1 Examples of use of the "rolling sphere method" for assessing a tall complex building for regions ...
- Annex B (informative) Guidance on the application of BS 6651 [Go to Page]
- 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
- 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
- B.8 Lightning protection system for a reinforced concrete chimney
- B.9 Down conductors in internal ducts
- B.10 Recommendations for lift installations
- 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
- 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... [Go to Page]
- C.1 General
- C.2 Application of this annex [Go to Page]
- Figure C.1 Strike location points to industrial installations which could affect electronic systems
- C.3 Basic considerations of electronic system lightning protection [Go to Page]
- C.3.1 Exposure levels
- C.3.2 Protection provided by the building [Go to Page]
- Figure C.2 Configurations involving electronic equipment
- Figure C.3 Lightning current distribution in a fifteen stanchion building
- Figure C.4 Plan view of fifteen stanchion building showing resulting field line plot (transfer�inductance co...
- C.4 Risk assessment [Go to Page]
- C.4.1 Decision to install lightning protection
- C.4.2 The probable number of lightning strikes [Go to Page]
- Table C.1 Effective collection area of mains services
- Table C.2 Effective collection area of data lines
- C.4.3 Vulnerability of the system configuration [Go to Page]
- Table C.3 Weighting factor
- 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 [Go to Page]
- Table C.6 Classification of structures and contents
- Table C.7 Classification of exposure level
- C.6 Sample calculations [Go to Page]
- Figure C.5 Collection area of structure and adjacent associated structure
- C.7 Methods of protection of installations against lightning [Go to Page]
- C.7.1 Earthing, bonding and potential equalization [Go to Page]
- Figure C.6 Cables entering a building separated from a transmitter mast
- Figure C.7 Bonding of cables and pipes at entry and exit to buildings
- C.7.2 Location of electronic equipment and cables
- C.7.3 Protection of building-to-building data lines [Go to Page]
- Figure C.8 Methods of reducing induced voltages
- Figure C.9 Hybrid earth system applied to equipment in multi-floor building
- 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...
- C.8 Characteristics and effects of lightning [Go to Page]
- C.8.1 Additional characteristics of lightning relevant to electronic equipment
- C.8.2 Strike points for lightning [Go to Page]
- Figure C.11 Direct injection into exposed electrical system
- Figure C.12 Protection from direct injection
- Figure C.13 Protection of cables located alongside tall vessels and bonding at roof level
- 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
- Figure C.16 Strike points on plant
- C.9 Lightning-induced transients and protection principles
- C.10 Sample calculations of induced voltage in instrumentation loops
- C.11 Sample calculation for protection of inner core(s) of coaxial cable
- C.12 Sample calculation of induced voltage in wiring
- C.13 Surge protection devices, location categories and testing [Go to Page]
- C.13.1 Location categories
- C.13.2 Magnitude of representative wave forms for testing mains surge protection devices [Go to Page]
- Table C.8 Location category A (mains)
- 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 [Go to Page]
- 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
- C.13.7 Combination wave test generator [Go to Page]
- Table C.12 Definitions of the waveshape parameters 1.2/50 4s [Go to Page]
- Figure C.17 Inductance
- Figure C.18 Simplified circuit diagram of the combination wave generator
- Figure C.19 Waveshape of open circuit voltage
- Figure C.20 Waveshape of short circuit current [Go to Page]