TOOLS IN CONSTRUCTION OF TRANSMISSION LINES

Basic tools needed to construct overhead transmission lines are as follows:

1. Conductor blocks
2. Overhead groundwire blocks
3. Catch-off blocks
4. Sagging blocks
5. Pulling lines
6. Pulling grips
7. Catch-off grips
8. Swivels
9. Running boards
10. Conductor lifting hooks
11. Hold-down blocks

Conductor blocks are made in the following configurations:

1. Single conductor
2. Multiple conductor
3. Multiversal type (can be converted from bundle to single, and vice versa)
4. Helicopter

Conductor blocks should be large enough to properly accommodate the conductor and be lined with a resilient liner such as neoprene or polyurethane and constructed of lightweight, high-strength materials.

Sheaves should be mounted on anti-friction ball bearings to reduce the tension required in stringing and facilitate proper sagging.

Conductor blocks are available for stringing single conductors or multiple conductors. Some are convertible, thus enhancing their versatility.

When stringing multiple conductors, it is desirable to pull all conductors with a single pulling line so that all conductors in the bundle have identical tension history. The running board makes this possible. Pulling lines are divided into two categories:
1. Steel cable
2. Synthetic rope

Because of the extra high tension required in transmission line construction, steel pulling lines and pilot lines are most practical to use. Torque-resistant, stranded, and swagged cable are used so that ball bearing swivels can be utilized to prevent torque buildup from being transferred to the conductor.

Some braided or woven steel cables are also used. If synthetic ropes are utilized, the most important features should include:

1. No torque
2. Very minimum elongation
3. No “kinking”
4. Easily spliced
5. High strength/small diameter
6. Excellent dielectric properties

Stringing overhead groundwires does not normally require the care of current-carrying conductors. Most overhead groundwires are stranded steel construction and the use of steel wire with a fiber optic core for communications has become a common practice.

Special care should be taken to ensure that excessive bending does not occur when erecting overhead groundwires with fiber-optic centers, such as OPT-GW (Optical Power Telecommunications — Ground Wire) and ADSS (All Dielectric Self-Supporting Cable).

Special instructions are available from the manufacturer, which specify minimum sheave and bullwheel diameter for construction. OPT-GW should be strung using an antirotational device to prevent the cable from twisting. 

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