From Build and Protect Winter 2019 issue 20
The earth experiences 100 lightning flashes per second and the U.S. alone has more than 40 million lightning strikes each year. Thunderstorms occur virtually everywhere and that puts just about any type of structure at risk to lightning damage.
Lightning can enter a structure in numerous ways, as illustrated in the above graphic. Since a single lightning strike is capable of introducing a chain reaction of destruction, the lightning protection system (LPS) design and installation needs to follow the guidelines of NFPA 780 to effectively address all aspects of this complex electrical hazard.
The design of the LPS must:
1) intercept the lightning flash (provide a preferred strike receptor)
2) conduct the current to earth
3) dissipate the current into the earth
4) create equipotential balance to prevent hazardous potential differences between the LPS, structure and its internal systems.
When considering all the factors associated with susceptibility, safety, and disruption, the cost of installing lightning protection is minimal as compared to the potential for loss and risk.