Protection Zone for Buildings Against Lighning Strokes Using Transmission Line Protection Practice

The nature of the zone of protection of structures from an elevated rod or wire, inadequately defined in the past, can be determined with high reliability using data developed by E.R.Whitehead of the Illinois Institute of Technology under contract from the Edison Electric Institute for the protection of high-voltage electric transmission lines. The vertical boundary of this zone of protection is not linear, as has been believed in the past, but is a circular arc, tangent to the ground, of 150-ft radius for 99.5 percent protection and 125-ft radius for 99.9 percent protection.