[ A_d = L \times W + 2 \times (L + W) \times H + \pi \times H^2 ]
The calculates zones protected by air terminals: A sphere of radius ( r ) (from table above) is rolled over the structure. Any surface touched by the sphere needs direct protection. 5. Down Conductor Spacing Number of down conductors required:
(approx.):
For an isolated rectangular building:
[ R = N \times P \times L ]
:
[ n = \fracPd ]
[ V_step = \fracI \cdot \rho2 \pi r ]