OPGW (Optical Ground Wire) cables play a dual critical role in modern power transmission systems: providing lightning protection for overhead lines and enabling high-speed communication through integrated optical fibers. The successful installation of OPGW cables requires meticulous preparation. Any oversight during the construction preparation phase can lead to catastrophic consequences, including cable damage, fiber breakage, structural failure, and project delays, resulting in significant economic losses. Unlike traditional ground wires, OPGW cables contain delicate optical fibers that are highly susceptible to damage from excessive bending, compression, or tensile stress. Comprehensive preparation during construction not only ensures compliance with technical standards but also minimizes operational risks, shortens installation time, and guarantees the long-term reliability of the communication infrastructure integrated into the power transmission network.
OPGW construction preparation
Storage and Transportation
OPGW fiber optic cable drums must be placed vertically during storage and transportation, and horizontal placement is not allowed. Measures to prevent movement should be implemented during storage and transportation. During transportation, appropriate cranes or forklifts should be used. For hoisting, suitable cable ropes should be passed through the drum axle holes to load and unload the drum horizontally. When using forklifts, the fork length should be greater than the drum width and correctly inserted at the drum edge. Contact with the outer layer of the OPGW fiber optic cable is not allowed. Damage to the drum and packaging should be avoided during storage and transportation. The specific handling method is shown in Figure.
Drum Assignment Verification and Testing
Before OPGW fiber optic cable installation, information such as drum assignment qualification should be verified. Each drum of fiber optic cable should be installed in the designated section according to the drum assignment table, and drum opening tests should be conducted using an Optical Time Domain Reflectometer (OTDR).
Construction Equipment
Tensioner
The diameter of the tensioner wheel must be greater than 70 times the diameter of the OPGW fiber optic cable and not less than 1200mm. The edge of the wheel must not have burrs or dents. The wheel groove should be covered with rubber or other suitable materials, and its dimensions should match the outer diameter of the OPGW fiber optic cable. A commonly used tensioner is shown in Figure.
Puller
The puller should have a grooved traction wheel structure, and the traction speed must be stable and variable. A commonly used puller is shown in Figure.
Pulling Rope
To effectively protect the fiber optic cable, a pulling rope must be used during the installation process. The OPGW fiber optic cable pulling rope is a low-twist structure steel wire rope connecting the puller and tensioner, used to pull the fiber optic cable. After pulling force is applied, the torque is small and it is not prone to forming kinks.
Stringing Pulley
The stringing pulley is a construction tool for fiber optic cable pulling. The pulley groove should be made of nylon or rubber material to protect the fiber optic cable. A commonly used stringing pulley is shown in Figure.
Pulling Grip and Swivel
The pulling grip connects the pulling rope and fiber optic cable through the pulley as a specialized connection tool, as shown in Figure.
The grip comes with an anti-bending connector and a rotating swivel to prevent the fiber optic cable from twisting during the pulling process, as shown in Figures.
Come-Along
The come-along is used to adjust the sag and tension of the OPGW fiber optic cable. A commonly used come-along is shown in Figure.
Construction Preparation Stage
Tensioning Site Layout
The tensioning site should be selected at an appropriate location to ensure the entrance and exit elevation angle is less than 25° and the horizontal deflection angle is less than 7°. The tensioning machine should be at least 2 times the tower height from the first tower. The cable drum support frame should be about 10m from the tensioner, and under site-constrained conditions, it must also be greater than 5m. The overall layout of the tensioning site is shown in Figure. When the site is limited, both the pulling site and tensioning site can be arranged by turning through turning pulleys. The setting of turning pulleys should be determined according to specific conditions.
Stringing Pulley Installation
For some tower positions, a single pulley is insufficient to bear the vertical load of the conductor, and double pulleys need to be set to reduce the load on a single pulley. This is generally used for tangent towers in mountainous terrain where the front and rear span distances are large and the tower itself is relatively high, while the positions of the front and rear towers are lower and bear greater pressure. When the wrap angle is greater than 30°, double pulleys need to be set to reduce the bending radius of the OPGW fiber optic cable on the pulley and prevent internal structural damage. When crossing highways, railways, and higher voltage grade power lines, double pulleys need to be set at the towers at both ends of the crossing span to improve the safety factor of the stringing pulley. When installing a single pulley, use a wire rope sling to connect the suspension point fitting and hang it at the suspension point, as shown in Figure1. When installing double pulleys, use two wire rope slings and use shackles to hang the stringing pulley on the construction hole of the ground wire peak or U-bolt, as shown in Figure2. The stringing pulleys at the 2 towers closest to the puller and
tensioner must be connected to ground wires.
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