: How far can the arrester be from the mast?
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: rolling sphere method calculator
[ d \leq \sqrtr^2 - (h - r)^2 - \sqrtr^2 - (H - r)^2 ] : How far can the arrester be from the mast