OPGW optical cable diversion applications

OPGW optical cable diversion involves rerouting or replacing the overhead ground wire while maintaining both grounding and communication functions.

Understanding OPGW

An Optical Ground Wire (OPGW) is a hybrid cable installed at the top of high-voltage transmission towers, combining lightning protection grounding with optical fiber communication capabilities . The cable typically consists of:

• Outer protective layer: Stranded aluminum or aluminum alloy wires for conductivity and corrosion resistance.
• Central tube: Stainless steel or aluminum housing the optical fibers, protecting them from moisture, mechanical stress, and temperature variations.
• Optical fibers: Usually single-mode fibers for long-distance, high-speed data transmission . OPGW serves as both a shield against lightning strikes and a high-speed communication channel for grid monitoring and control.

Reasons for Diversion

Diversion of OPGW may be required due to:

• Tower modifications or relocation
• Replacement of damaged or aged cables
• Upgrading to higher fiber count or improved mechanical design
• Construction of new transmission lines intersecting existing routes

Diversion Procedure

1. Planning and Safety:
   • Conduct a detailed survey of the existing line and towers.
   • Ensure power line de-energization if necessary, and follow strict safety protocols, including personal protective equipment for high-voltage work .
2. Mechanical Preparation:
   • Secure the existing OPGW with clamps or temporary supports.
   • Measure and mark the length of cable to be stripped or rerouted.
   • Remove outer aluminum or steel layers carefully using metal saws or grinders, taking care not to damage the optical fibers .
3. Splicing and Fiber Management:
   • Use fusion splicing to connect the optical fibers of the diverted cable to the existing network.
   • Employ appropriate closures (heat-shrink tubes, splice trays, or branch joint closures) to protect fibers from environmental exposure and mechanical stress .
   • Ensure proper anchoring of closures to towers using galvanized steel clamps or stainless steel hardware .
4. Installation on Towers:
   • Mount the diverted OPGW along the tower tops, maintaining proper sag and tension to prevent mechanical strain.
   • Ensure electrical continuity for grounding and lightning protection.
   • Test optical fiber transmission to verify signal integrity before finalizing the installation .
5. Final Checks:
   • Inspect mechanical attachments, grounding continuity, and fiber splices.
   • Confirm that the cable is free from excessive tension, kinks, or abrasion points.
   • Document the diversion for maintenance records and future reference.

Key Considerations

• Fiber Protection: Optical fibers are sensitive to strain; loose-tube construction in OPGW prevents fiber damage during handling .
• Weather and Environmental Conditions: Diversion should account for wind, ice, and temperature variations affecting cable tension.
• Simultaneous Functions: The diversion must maintain both grounding and communication functions without interruption.
• Equipment: Specialized pulling equipment, tensioners, and aerial devices may be required for safe handling of long spans . By following these procedures, OPGW diversion can be performed safely and efficiently, ensuring continued protection of the transmission line and uninterrupted communication for grid operations.