This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
As a general rule, the poles should be set from 100 to 125 feel apart, which is equivalent to 53 to 42 poles per mile.
Under certain conditions, these spacings given will have to be modified; but if the poles are spread too far apart, there is danger of too great a strain on the poles themselves, and on the cross-arms, pins, and conductors. If, on the other hand, they are placed too close together, the cost is unnecessarily increased.
Fig. 60. Plan View, Cover, and Section of Double Cut-out Box.
The size and number of conductors, and the potential of the linework, determine to a great extent the distance between the poles; the smaller the size, the less the number of conductors; and the lower the potential, the greater the distance between the poles may be made. Of course, the exact location of the poles is subject to variation because of trees, buildings, or other obstructions. The usual method employed in locating poles, is first to make a map on a fairly large scale, showing the course of the linework, and then to locate the poles on the ground according to the actual conditions.