what kind of stringing equipment and accessories for overhead power transmission lines construction?
Tools
Basic tools needed to construct overhead transmission lines are as follows:
Conductor blocks
Overhead groundwire blocks
Catch-off blocks
Sagging blocks
Pulling lines
Pulling grips
Catch-off grips
Swivels
Running boards
Conductor lifting hooks
Hold-down blocks
Conductor blocks are made in the following configurations:
Single conductor
Multiple conductor
Multiversal type (can be converted from bundle to single, and vice versa)
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:
Steel cable
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:
No torque
Very minimum elongation
No "kinking"
Easily spliced
High strength/small diameter
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.