Transmission tower parts and types of Transmission towers

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Transmission Towers: Parts, Design, and Types Explained

High-voltage power transmission is the backbone of modern electricity networks. To transmit power over long distances, transmission lines are laid, and these lines are supported by transmission towers, also known as pylons.



Transmission towers serve two primary purposes:

  1. To safely separate high-voltage conductors from surroundings and from each other.

  2. To keep conductors at sufficient height above the ground, ensuring safety and reliability.

Most overhead transmission lines carry three-phase power using three conductors or bundles of conductors. Typically, ACSR (Aluminum Conductor Steel Reinforced) is used: a steel core provides strength, while surrounding aluminum wires offer high conductivity with low resistance.

Key Parts of a Transmission Tower

A transmission tower is an engineered steel structure designed to withstand natural calamities, wind loads, and conductor tensions. It is made of several essential parts:

  1. Tower Top – Holds the earth/shield wire to protect conductors from lightning strikes.

  2. Cross Arm – Carries insulators that support conductors. Its size depends on transmission voltage.

  3. Beam – The section connecting and supporting the cross arms.

  4. Insulator Strings – Carry transmission lines; their number increases with voltage level.

  5. Cage (K-Frame / Fork) – The main structural frame providing overall support.

  6. Tower Body & Legs – Provide ground clearance; higher voltage requires higher clearance and wider leg spacing.

  7. Tower Base – Anchors the tower to the foundation, ensuring stability.

  8. Vibration Dampers – Prevent fatigue due to wind-induced conductor vibrations. Two types are used:

    • Stockbridge (VORTX) Dampers – Most common type.

    • Spiral Dampers – Used in special cases.



Transmission Tower Height Considerations

The height of a transmission tower is a critical design factor and depends on:

  • Minimum ground clearance (higher voltage → greater clearance).

  • Conductor sag (sag cannot be eliminated, only minimized).

  • Vertical spacing between top and bottom conductors.

  • Gap between ground wire and top conductor.

➡ A typical horizontal configuration transmission tower is about 100 feet high, designed to bear both vertical loads (conductor weight) and horizontal loads (wind forces).

Types of Transmission Towers

Transmission towers are classified based on line deviation angles, function, and design:

  • Suspension / Tangent Towers (< 2°) – For straight-line runs.

  • Small Angle Towers (2° – 15°) – For minor deviations.

  • Medium Angle Towers (15° – 30°) – For moderate deviations.

  • Large Angle Towers (30° – 60°) – For sharp deviations.

  • Dead-End Towers (> 60°) – For terminating lines or major direction changes.

  • Transposition Towers (4 Cross-Arms) – Used to interchange conductor positions to balance line parameters.

  • Special Towers – JC, MC, NB, NBMC types for specific site requirements.

  • Pole-Mounted Termination Towers – For compact spaces or urban terminations.

  • Monopoles – Single-pole steel towers, aesthetically suited for cities.

Final Thoughts

Transmission towers are a critical part of the power transmission system, ensuring safe, reliable, and efficient delivery of electricity across long distances. Their design depends on voltage level, terrain, weather conditions, and line configuration.

Modern innovations like monopole towers and compact designs are increasingly used in urban areas to save space while maintaining reliability.


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