Lightning Protection of Buildings

Extending initial work on this subject, which developed the circular-sided conical zone of protection below and around grounded high objects, the interrelationship between stroke current magnitude and radius of the sides of the cone is developed. Further, the minimum magnitude of stroke current which is likely to be damaging to structures is determined to be approximately 10 000 A for which the critical radius for 99.5 percent protection is 150 ft (45 m).