Overhead conductor installation is a critical phase of power line construction. The process is also known as "tension stringing" because it involves installing conductors while keeping them under constant tension. This method is used to keep the conductor off the ground, preventing damage and ensuring safety. A typical project involves a coordinated sequence of operations with specialized machinery.

Phase 1: Preparation and Setup

Before any pulling begins, the site and equipment must be properly prepared.

1. Surveying and Route Planning: The final sag and tension of the conductor are calculated for the entire span.

2. Tower & Insulator Installation: Towers or poles are erected, and OHTLstringingequipment.com/Stringing-Blocks--Sheaves.html target='_blank'>Stringing Blocks (sheaves) are installed on the arms of the towers.

3. Equipment Setup: A hydraulic OHTLstringingequipment.com/Hydraulic-Conductor-Tensioners.html target='_blank'>Tensioner is positioned at the start of the section, and a hydraulic puller is set up at the end of the section. The conductor reels are placed on hydraulic drum stands near the Tensioner.

Key Equipment:

• Hydraulic drum stands: For safely and efficiently handling and unwinding large conductor reels.

• Stringing Blocks: These are critical for guiding the conductor through the towers while minimizing friction.

• Hydraulic Puller-Tensioners: Many modern machines combine the functions of both a puller and a tensioner in a single unit.

Phase 2: Pilot line stringing

Before the heavy conductor can be installed, a lighter pilot line must be run.

1. Pilot Line Pulling: The pilot line is a lightweight, anti-twisting rope (often braided steel or synthetic). A puller draws this line from the tensioner, running it through all the stringing blocks along the entire section.

2. Running Grounds: For safety, running grounds are attached to the pilot line and the main pulling rope to ensure the line is grounded throughout the process.

Key Equipment:

• Pilot Line Pullers: Smaller, high-speed machines designed specifically for pulling pilot lines.

• Anti-Twisting Braided Steel Ropes: Used as the pulling line due to their high strength and resistance to twisting.

Phase 3: conductor stringing and Sagging

This is the main event of the installation, requiring synchronized operation of the puller and tensioner.

1. Connecting the Conductor: The pulling rope is connected to the conductor using a conductor pulling grip and a Swivel. The Swivel is essential to prevent any twist in the pulling rope from being transferred to the conductor.

2. The Pulling Process: The puller at one end begins to pull the rope, while the tensioner at the other end applies a controlled back tension to the conductor drum. This keeps the conductor elevated off the ground and prevents it from being scuffed or damaged.

3. Sagging: Once the conductor is in place, it is brought to its final sag and tension. This is a crucial step that is verified using a pre-calculated sag chart based on temperature and span length.

Key Equipment:

• Hydraulic Pullers and Tensioners: The core equipment for controlling the stringing operation.

• Swivels: A seemingly simple component that is vital for preventing conductor damage.

• Conductor pulling grips: Used to securely connect the conductor to the pulling rope without causing damage.

Phase 4: Finalization

Once the conductor is properly sagged, the final steps can be completed.

1. Clamping (Clipping-in): The conductor is removed from the temporary stringing blocks and permanently secured to the insulators on the towers.

2. Splicing and Dead-Ending: Any required mid-span splices are made, and the conductor is terminated at the end towers.

3. Removal of Equipment: All temporary equipment, including stringing blocks and running grounds, is removed.