Rolling Sphere Method Calculator -

: Never trust manual approximations for critical infrastructure. Run the rolling sphere simulation, verify the red zones, and then build with confidence. About the author: This article is based on principles from IEC 62305 and IEEE 998. Always consult local codes and a licensed engineer for final designs.

The sphere’s radius is not arbitrary. It is derived from the formula, which relates to the peak lightning current. The most common standard (IEC 62305 and NFPA 780) defines protection levels (I to IV) with corresponding sphere radii: rolling sphere method calculator

A smaller sphere (Level I) is more "touchy" and will probe into every crevice, providing the highest level of protection. A larger sphere (Level IV) offers less stringent protection, suitable for ordinary structures. The Core Equation To determine if a point at height ( H ) is protected by a lightning mast of height ( h ) (with ( h > H )), the horizontal distance ( d ) from the mast to the point must satisfy: Always consult local codes and a licensed engineer

: How far can the arrester be from the mast? The most common standard (IEC 62305 and NFPA

But manual RSM calculations are tedious and error-prone. Enter the —a digital tool that transforms complex 3D geometry into actionable protection zones. This article explains the physics behind the method and how to leverage a calculator for real-world designs. The Physics: Why a Sphere? The Rolling Sphere Method is based on a simple premise: Imagine a sphere of a fixed radius, ( r ), rolling over the terrain and over the structure in question. Where the sphere touches the ground or a lightning protection system (LPS), it represents a point a lightning leader could attach. Any volume that the sphere cannot touch (because it is shielded by a mast, air terminal, or the ground itself) is considered protected.

[ d \leq \sqrtr^2 - (h - r)^2 - \sqrtr^2 - (H - r)^2 ]