Types and Design Classification of Overhead Transmission Towers

Transmission Towers Overview

Main Types of Transmission Towers

1. Suspension Towers

2. Tension Towers

3. Terminal Towers

4. Transposition Towers

5. Self-Supporting Towers

• Narrow Base Towers: Small base size, integrated single foundation for four legs. Adopts angle steel lattice bolted structure. Suitable for urban areas with limited land and high land cost, saving steel consumption but with higher foundation cost.
• Broad Base Towers: Large base size, independent separate foundations for each leg. Consumes more steel but features lower foundation cost, suitable for spacious areas with low land cost.
• Tangent Towers: Used for straight line sections, equipped with vertical suspension insulators.
• Deviation Towers: Used for line direction changes, equipped with tension insulators.

6. Guyed / Stayed Towers

• Portal Structure Type: Two legs connected by cross arms at the top, fixed with guy wires and double leg foundations.
• V Structure Type: Two legs arranged in an angled V-shape with an integral heavy foundation, stabilized by multiple guy wires.

7. A / B / C / D Type Towers

• A Type Tower: Suspension type, applicable for line deflection of 0–2°.
• B Type Tower: Tension type, applicable for line deflection of 2–15°.
• C Type Tower: Tension type, applicable for line deflection of 15–30°.
• D Type Tower: Tension type, applicable for line deflection of 30–60°.

8. Circuit Classification Towers

• Single Circuit Tower: Carries only one set of transmission line conductors.
• Double Circuit Tower: Carries two sets of transmission line conductors.
• Multi Circuit Tower: Carries more than two sets of transmission line conductors.

9. Special Crossing Towers

• River Crossing Towers: Suspension or tension type with 0° deflection; modern design supports a span up to 800m.
• Railway Crossing Towers: Tension type, crossing railways at right angles, with strict standards on tower distance, conductor height and limited span length.
• Road Crossing Towers: Tension type with double tension hardware and double insulators for safety; fixed minimum height between conductors and road surface, and limited span length within 250m.