Transmission lines are composed of five main parts: conductors, fittings, insulators, towers and foundations. Transmission towers are an important part of supporting transmission lines, accounting for more than 30% of project investment. The choice of transmission tower type depends on the transmission mode (single circuit, multiple circuits, AC/DC, compact, voltage level), line conditions (planning along the line, buildings, vegetation, etc.), geological conditions, topographical conditions and operating conditions. The design of transmission towers should meet the above requirements, and be carefully designed on the basis of comprehensive technical and economic comparisons to achieve safety, economy, environmental protection, and beauty.
（1）Requirements for transmission tower planning and selection to meet electrical requirements:
1. Electrical clearance
2.Line spacing (horizontal line spacing, vertical line spacing)
3.Displacement between adjacent lines
4.Protection angle
5.String length
6.V-string angle
7.Height range
8.Attachment method (single attachment, double attachment)
（2）Optimization of Structural Layout
The structural layout should meet the requirements of operation and maintenance (such as setting up ladders, platforms, and walkways), processing (such as welding, bending, etc.), and installation while ensuring safety.
（3）Material Selection
1. Coordination
2. Structural requirements
3. Proper tolerance should be considered for hanging points (directly subjected to dynamic loads) and variable slope positions.
4. Components with opening angles and structural eccentricity should have tolerance due to initial defects (reducing load-bearing capacity).
5. Caution should be exercised in material selection for parallel-axis components, as repeated tests have shown failure of such components. Generally, a length correction factor of 1.1 should be considered for parallel-axis components, and torsional instability should be calculated according to the "Steel Code.”
6. Tensile rod elements should undergo block shear verification.
Post time: Aug-15-2023
