While both scenarios involve stringing OPGW, installing on a brand-new transmission line and retrofitting an existing ground wire present distinct methodological differences, primarily due to the presence (or absence) of an existing energized power system and infrastructure.

I. Stringing OPGW on a Brand-New Transmission Line:

• Context: This scenario involves stringing OPGW alongside new phase conductors on newly erected towers, where the line is not yet energized.

• Methodology:

  • Conventional Tension Stringing: This is the most common method. After towers are erected, pilot ropes are strung (often by drone or manually), followed by pulling ropes, and then the OPGW. Phase conductors are typically strung either before or after the OPGW, depending on the sequence defined by the project.

  • No Live-Line Constraints: Since the line is de-energized, minimum approach distances (MAD) to existing energized conductors are not a concern (unless there are nearby existing active lines in the corridor). This simplifies safety protocols related to electrical hazards.

  • Clearer Right-of-Way: The right-of-way is usually clear of existing conductors, allowing for more straightforward equipment placement and less risk of accidental contact with other live components.

  • Parallel Stringing: Sometimes, multiple conductors and OPGW can be strung in parallel using specialized running boards and multiple pulling/tensioning machines, increasing efficiency.

• Equipment Implications:

  • Our full range of hydraulic pullers and tensioners, conductor stringing blocks, reel stands, and pulling ropes are utilized. The equipment capacity is determined by the span lengths and OPGW weight/tension requirements.

II. Replacing an Existing Ground Wire with OPGW (Retrofit/Reconductoring):

• Context: This involves removing an old, de-energized or, more commonly, energized overhead ground wire and replacing it with OPGW, often while the phase conductors below remain energized. This is a more complex and high-risk operation.

• Methodology:

  • "Live-Line" or "Hot Stringing" Techniques (Most Common):

    • Carrier Method: A self-propelled carrier or robot travels along the existing ground wire, pulling a pilot rope and positioning specialized double pulleys. The old ground wire is then used as a pulling rope to pull in the new OPGW, simultaneously removing the old wire from the other end. This method significantly reduces outage requirements.

    • Direct Replacement Method: Involves pulling the new OPGW directly in place of the old ground wire, often using specialized clamps that grip both the old and new wires.

    • Insulated Tools and Equipment: All equipment and ropes must be designed for live-line work, featuring high dielectric strength and proper insulation.

    • Strict MAD Adherence: Maintaining minimum approach distances to the energized phase conductors below is absolutely critical. All personnel must be highly trained in live-line safety.

    • Temporary Grounding: Careful grounding and bonding procedures are implemented at each structure where work is being performed.

  • De-energized Replacement: If an outage is granted, the existing ground wire and potentially the phase conductors are de-energized and grounded. This simplifies safety, but outages are costly.

• Equipment Implications:

  • Specialized "Live-Line" OPGW Stringing Equipment: This includes insulated puller-tensioners or standard units with strict grounding protocols, insulated stringing blocks, self-moving traction machines (robots) that travel on the existing ground wire, and insulated pulling ropes.

  • Anti-Twisting Devices: Even more critical to prevent torsional transfer during the simultaneous removal/installation process.

  • Enhanced Communication Systems: Robust, clear communication among all crews is paramount due to the higher risk.

  • Precision Control: Pullers and tensioners with advanced feedback and automatic control are vital to manage tensions within strict limits, especially when pulling against the resistance of the old wire.

Our company specializes in providing the full range of both conventional and advanced "live-line" OPGW stringing equipment and tools, enabling our clients to execute new line installations or complex retrofit projects safely and efficiently, regardless of whether the line is energized or de-energized.