While "Anti-Vibration Dampers" are typically installed after the primary stringing and sagging is complete, they are considered essential "Cable Stringing Accessories" because they are a crucial, permanent component for ensuring the long-term mechanical integrity and lifespan of overhead conductors. Their primary function is to mitigate conductor vibration that can lead to fatigue damage.

Why They Are Essential:

• Fatigue Protection: Overhead conductors are susceptible to Aeolian vibration (wind-induced oscillation) and sub-span oscillation (in bundled conductors). Without damping, these continuous vibrations can cause:

  • Fatigue Breakage: Repeated stress cycles can lead to fatigue failure of individual strands, particularly at suspension clamps or points of stress concentration.

  • Damage to Hardware: Vibration can also loosen or damage insulators, clamps, and other line hardware.

  • Arcing Damage: In severe cases, vibration can cause clashing of conductors within a bundle, leading to arcing and localized heat damage.

• Extended Conductor Lifespan: By effectively dampening vibrations, these accessories significantly extend the operational life of the conductor, reducing maintenance costs and ensuring grid reliability.

• Improved System Reliability: Preventing conductor fatigue failures means fewer unscheduled outages, enhancing the overall reliability and availability of the transmission line.

Common Types of Anti-Vibration Dampers:

• Stockbridge Dampers: The most common type. They consist of a central clamp that attaches to the conductor and two masses (often made of cast iron or zinc alloy) connected by a steel messenger cable. When the conductor vibrates, the damper's masses vibrate out of phase with the conductor, dissipating the vibratory energy. They are highly effective over a broad range of frequencies.

• Spiral Vibration Dampers (Helical Dampers): Made from a resilient, non-metallic material (e.g., PVC, HDPE) in a helical shape. They are wrapped around the conductor and dissipate vibration energy through friction and impact with the conductor. They are typically used on smaller conductors and distribution lines.

• Spacer Dampers: Used exclusively on bundled conductors. They serve a dual purpose:

  • Maintain Bundle Geometry: Physically separate and maintain the precise spacing between individual conductors within a bundle.

  • Dampen Sub-span Oscillation: Incorporate elastomeric or hinged components that absorb and dissipate energy from oscillations between the individual conductors within a bundle.

• Mid-Span Dampers: Less common, but used to address specific vibration issues in very long spans.

The correct selection and precise placement of these dampers, based on conductor type, tension, span length, and wind data, are critical engineering considerations for any successful OHTL project.