e)

The height of the masts is determined by the Equation:

where "M" is the height of the masts, "S" is the height of the assumed salient

plane, "D" is the mast spacing on the diagonal axis as determined by

Equation (1), with C = 40 ft (12 m). "P" is given an empirical value (see

Appendix A, A-1) according to the value of "D" as calculated from Equation

(1).

The height of the masts as determined by the formulae is based on the

condition that the structure to be protected is located between two parallel

rows of masts. To determine the height of the masts, use Equation (1), and

using C = 40 ft (12 m), calculate for D, and then determine M by using the

curves of Appendix A, A-2, Chart No. 1.

f) The protection of a structure by self-standing vertical masts

dictates that the distance from the center line of the structure or complex to

the masts on the normal or the diagonal axis must not be more than 100 ft

(30.5 m). When this condition cannot be met, the protection of the structure

or complex will be by overhead ground wiring. To determine the final

distance, D1, along the diagonal axis, use Equation (1) substituting D1 for D,

with C values between 6 ft (1.8 m) minimum to 25 ft (7.6 m) maximum. D1 shall

not exceed 100 ft (30.5 m).

g) When overhead ground wiring are used for protection, support the

overhead ground wiring on masts located at the vicinity of the protected

structure at distances from the structure established as 6 ft (1.8 m) minimum

to 25 ft (7.6 m) maximum. The lowest point of mid-span sag in the overhead

ground wiring above the salient plane of the protected structure is to be no

less than 10 ft (3.05 m). Increase the distance of cable which is run

parallel to the structure by 1 ft (0.3 m) for each 10 ft (3.05 m) of

horizontal cable greater than 50 ft (15 m). Determine mid-span sag of the

overhead ground wire from the curves of Appendix A, A-2.

4.

Graphic Examples. In Appendix A, A-3, Example 1: L, W, and S are

known, C is given the value of 40, B = 18 ft (explained in Appendix A, A-1,

Definitions of Terms), and N is equal to 6. In Equation (1) substitute these

values and D is found to equal 98.5 ft. In Appendix A, A-1, refer to the

curves at point 98.5 ft (30 m) on the horizontal scale, then extend vertically

to the 50 ft slant line, and carry horizontally to the vertical scale, again

using Equation (1) and substituting actual distance C = 6 ft (1.8 m) minimum

to 25 ft (7.6 m) maximum, this will show a mast height of 95.5 (29 m).