My regards;
The number of down
conductors can be determined as follows:
1-One conductor for a structure whose base area does not
exceed100 sq m
2-Determine the whole numbers N1 and N2, and select the
smaller of the two
N1=1+(A-100)/300
N2=P/30
Where N=whole number
of the working area
A=base
area of the structure in sq m
P=perimeter of the structure in m
3-Where the height of the structure is more than 30m in
height, additional considerations to
the above should be applied.