# One high lightning rod or several low ones?

When choosing the design of external lightning protection, designers are increasingly opting for high lightning rods. The reason is that they are in doubts about the reliability of meshed cages or a series of lower lightning rods. Is their choice right? Can a single high air terminal reliably protect a facility?

Professor E. M. Bazelyan's article on our website about the lightning protection of residential and public buildings tackles this issue.

It includes an example of designing an external lightning protection system for the building having dimensions of 60x20 meters and a height of 20 meters.

If you place a high lightning rod on the building (as shown in a figure above), then calculations show that its height should be 54 meters*. The number of lightning strikes into such a lightning rod in the specified area is defined by a contraction area of SM = 9πh2 ≈ 0,082km2, which is almost 4 times the contraction area of the protected building itself (without lightning protection). It turns out that when installing a high lightning rod, the number of adjacent lightning strikes increases almost fourfold! Of course, designers and building owners will hardly be satisfied.
In this case, it is better to use an external lightning protection system based on several lightning rods.

ZANDZ specialists assist in the design, selection, and installation of grounding and lightning protection systems. Contact us and we will surely help!

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