Structural lightning protection design considerations

\| \| Flat Tape System \| Solid Circular System \| Cable and Wire System \| Accessories \| \| How to apply lightning protection \|
Structural lightning protection design considerations

BS 6651 (Protection of structures against lightning) clearly advises strict adherence to the provision of a conventional Lightning Protection System (LPS) to the total exclusion of any other device or system for which claims of enhanced protection are made. Principle components of a conventional structural lightning protection system, in accordance with BS 6651 are: Air termination network Down conductors Earth termination network Bonding (to prevent side flashing)
Air termination network
On high risk structures such as explosive factories, no part of the roof should be more than 2.5m from an air termination conductor. This is generally achieved by applying a 5m x 10m mesh to the roof. However, for most structures, a mesh of 10m x 20m is considered sufficient, giving a maximum distance from any part of the roof to the nearest conductor of 5m.
The `Zone of Protection' offered by an air termination network is considered to be 45° for heights up to 20m. Above this height, the zone of protection is determined by the `Rolling Sphere Method'. This involves rolling an imaginary sphere of 60m radius over a structure. The areas touched by the sphere are deemed to require protection. On tall structures, this can obviously include the sides of the building.