Overhead Power Line Stringing Equipment

Overhead power line stringing equipment comprises the essential tools and machinery used to install and tension conductors safely and efficiently on overhead transmission and distribution lines. This equipment ensures proper conductor sag, alignment, and tension during the stringing process.

Core Components of Overhead Power Line Stringing Equipment

• Tensioners: These are the most critical devices, applying controlled tension to conductors during installation to prevent sagging or damage. Modern hydraulic tensioners feature closed hydraulic circuits with infinitely variable tension control, automatic safety brakes, and wear-resistant bullwheel linings (e.g., MC nylon) to protect conductors. They can handle bundled conductors and are often mounted on trailers for mobility.

• Pulling Lines (Bull Lines): Strong ropes or steel pilot wires used to pull conductors through stringing blocks. Pilot wires are often galvanized steel braided ropes designed to prevent conductor twisting during installation, especially in rugged or challenging terrain.

• Stringing Blocks (Pulleys): These guide conductors and pulling lines over poles or towers, reducing friction and preventing conductor damage. High-quality blocks use ball bearings for efficient sheave rotation, typically causing only about 2% friction loss per block. Larger diameter blocks are used at critical points such as lead poles or sharp angles.

• Pullers: Machines that pull the conductor or pulling line through the stringing blocks. Pullers work in coordination with tensioners and stringing blocks to maintain proper tension and smooth conductor movement.

• Come Along Clamps and Cable Grips: Used to securely hold conductors or earth wires during stringing operations, available in manual and automatic types suited for various conductor sizes.

• Reel Stands and Winches: Reel stands hold conductor reels with braking systems to control payout, while winches assist in pulling conductors over long distances or difficult terrain.

• Swivels and Anti-Twisting Devices: These prevent conductor twisting and birdcaging by allowing rotation during pulling.

Features and Applications

• Equipment is designed to string conductors for voltages ranging from low-voltage distribution lines to ultra-high voltage transmission lines (e.g., 800 kV), including bundled conductors.

• Hydraulic tensioners and pullers provide adjustable tension and pulling forces, with safety features such as automatic over-pull protection and hydraulic brakes.

• Pilot wire systems, such as the "Spider System," use multiple colored ropes to string phase conductors and neutrals sequentially, improving efficiency and safety.