TRANSMISSION LINES POLES SELECTION BASICS AND TUTORIALS

The ability of a pole to be self-supporting depends on the class of the pole and the load it must carry (ignoring for the present the characteristic of the soil).

Classes of Poles
All wood poles are divided into classes based on thickness and circumference. One system uses five classes: 5, 4, 2, 0, and 00, ranging from moderately thin (class 5) to extra heavy (class 00). Knowing the load, it is possible then to select the proper class of pole for each location and degree of loading.

If the number of units of loading is greater than the number of units the pole can support by itself, either the pole must be guyed or the conductors slackened to reduce the tension.

Heavier-class Poles
Poles one class heavier than the class specified by the tables should be used for each of the following purposes:

1. Junction poles

2. Poles supporting alley or side arms

3. Poles supporting line disconnects (except in-line types) or fuse cutouts

In addition, a pole of at least class 4 should be specified for deadend poles, angle poles, and transformer (or capacitor, regulator, or other equipment) poles.

Extra Heavy-class Poles
Class 0 and class 00 poles are special oversize poles and are used primarily in the following situations:

1. In place of sidewalk guys, the most expensive guys to install

2. At an angle in the line in place of the combination of a span guy with a stub pole and sidewalk guy on the opposite side of the road

3. At T intersections, where normally a sidewalk guy or a span guy with a stub pole would be used

4. Where guying permission or rights cannot be obtained

5. To satisfy consumer complaints, by replacing an existing or proposed anchor guy.

Selecting the Guy Wire
When the loading exceeds the strength of a pole, the pole should be guyed. The physical location of the pole in the field will determine what type of guy should be used: anchor, span, head, or sidewalk type.

Guy protectors should be installed on all anchor guys accessible to the public. When a pole line changes direction and the turn angle is less than 60°, the corner, or “pivot,” pole may be guyed with a single guy bisecting the angle. At angles greater than 60°, the pole should be guyed against the stress in each direction.

Selecting the Anchor
Anchors come in many types and sizes, each designed for certain soil and guying conditions. While each will do its specific job better than another design of anchor, most find use under more than one set of conditions.

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