How Are Transmission Towers Built?
In modern power systems, transmission towers are critical infrastructure for the long-distance transmission of high-voltage electricity. Like massive steel giants, they support the nation's power grid, traversing cities, mountains, deserts, and rivers to deliver electricity to every household. But perhaps you're wondering: How are transmission towers built?
Building a transmission tower involves more than just stacking steel structures; it also involves preliminary design, site selection, precision manufacturing, complex transportation, and challenging on-site construction. This article, from the perspective of a professional manufacturer, systematically explains how transmission towers are constructed, step by step, to help you fully understand the engineering logic behind tower construction.
Transmission Tower Pre-Construction Preparation
Before any construction begins, thorough and professional preparation determines the stability, safety, and long-term performance of the entire transmission tower.
Site Selection And Geological Survey
The site selection of a transmission tower is a key component of the entire transmission line design. The tower's location not only determines the conductor's routing and span, but also directly impacts the construction difficulty and subsequent operation and maintenance efficiency.
First, the line's route must be carefully considered: densely populated areas, cultural heritage sites, high-pressure gas pipelines, railways, airports, and high-risk geological zones must be avoided. The ideal site should minimize construction costs and maximize maintenance convenience.
Geological surveys are also crucial. Through drilling sampling, compression testing, and seismic intensity analysis, engineers assess key indicators such as foundation bearing capacity, hydrological conditions, and soil type. In mountainous areas or seismic zones, they even need to assess risks such as landslides and mudslides.
Furthermore, the impacts of wind loads, ice thickness, and thermal expansion on the tower structure must be calculated to provide parameters for subsequent structural design.
Structural Design and Standard Determination
Tower type selection and structural design are the most critical technical aspects of "how do they build transmission towers?"Transmission tower design requires a comprehensive consideration of the following factors:
- Voltage level (110kV, 220kV, 500kV, or even 1000kV)
- Number of circuits (single, double, or multiple)
- Terrain type (plain, hilly, plateau, mountainous)
- Climatic conditions (wind speed, icing, lightning frequency)
- Conductor type and sag requirements
Common tower types include straight towers, tension towers, corner towers, and terminal towers, each with distinct structural characteristics. For example, high-pressure tension towers typically utilize steel tubular structures to enhance tensile strength, while straight towers often utilize angle steel structures for more economical manufacturing and installation.
Designers must adhere to national standards (such as China's DL/T 5154) or international standards (such as IEC 60826) and conduct detailed design in accordance with the specific technical specifications of the power company.
Transporting a Transmission Tower
After the tower is fabricated, efficiently and safely transporting hundreds of components to the construction site, especially in mountainous or remote locations, is a significant challenge.
The first step is component packaging. Each angle steel, flange, and bolt package must be numbered and categorized to ensure alignment with the installation drawings and avoid confusion on site. The outer packaging is made of moisture-proof and impact-resistant materials to prevent damage and rust during transportation.
Transportation plans are tailored to local conditions. In areas with accessible highways, large trucks can be used for full-load transport. However, in mountainous and forested areas, light trucks, multi-wheel trailers, or even helicopters or cable cars are often needed for transport uphill.
Transportation routes must be surveyed and planned in advance to confirm bridge load capacity, curve radius, and grade restrictions. Transportation permits must also be obtained from local governments to avoid delays in construction.
How Do They Build Transmission Towers On Site?
Entering the on-site construction phase marks the transition of the tower construction project from blueprints to reality. The construction process is divided into three core stages: foundation construction, tower assembly, and hoisting.
Foundation Construction And Tower Footing
Based on the geological survey report, the construction team will excavate the foundation pit, tie the reinforcement, erect formwork, and pour the concrete tower footing. Common foundation types include independent foundations, pile foundations, and raft foundations, with the choice based on the bearing capacity of the foundation and the terrain.
The tower body can only be installed after the foundation reaches 100% of its design strength. This period typically takes 7 to 14 days, during which time maintenance, rain protection, and frost protection measures must be implemented.
Tower Assembly and Installation Methods
Transmission towers can be assembled in two main ways:
- Ground Assembly + Overall Hoisting: The entire tower or partial tower structure is pre-assembled on the ground near the foundation, then hoisted to the tower base using a crawler crane or truck crane. This method offers advantages such as increased safety and construction efficiency, but also requires a larger site.
- Segmental Assembly + Segmental Hoisting: The tower is assembled section by section at the tower base (tower legs, tower body, tower head). Each completed segment is hoisted to its designated location and then secured. This method is suitable for areas with narrow terrain or mountainous areas.
Throughout the installation process, technicians use total stations or laser rangefinders to ensure the tower's verticality, connection angles at each node, and torque standards meet standards. For high-voltage lines, structural accuracy directly impacts electrical safety.
Safety and Technical Assurance During Transmission Tower Construction
Transmission tower construction heights typically exceed 30 meters, and UHV towers can reach heights exceeding 80 meters. Safety must be a top priority.
Risk Control For Working At Height And Live Electrical Lines
- A full fall protection system (safety belt, restraining rope, and fall arrester) must be used for working at height.
- Every construction worker must complete specialized height work training and obtain a certification before performing their duties.
- Power grid transformation projects require consideration for working near live electrical lines, requiring the installation of insulating shields or requesting temporary power outages.
Technology-Assisted Construction Improves Efficiency And Safety
- Drone inspections: Used for aerial surveys, monitoring construction progress, and inspecting welding quality.
- BIM (Building Information Modeling): 3D modeling enables pre-construction visualization and reduces rework.
- Tower deformation monitoring sensors: Installed at key locations, they provide real-time detection of deflection caused by wind pressure or construction stress.
These technologies have significantly enhanced the intelligent construction of modern transmission towers and reduced human error.
Construction Differences Between Different Types Of Transmission Towers
The construction of transmission towers varies not only by voltage level but also significantly by the terrain and surrounding environment:
- In urban areas: The tower must be aesthetically pleasing and occupy a small footprint. Steel tubular towers or steel column towers are often used, and installation must be coordinated with transportation and pipeline relocation.
- In mountainous areas: Foundation preparation is complex, requiring the construction of construction access roads, cableway transportation, and segmented assembly. Tension towers are also relatively heavy.
- In offshore/wetland areas: Deep piles or caisson structures are required for foundations in soft soils. Construction requires the use of floating cranes and piling platforms.
Conclusion
Through this in-depth analysis, I believe you now have a clear understanding of how transmission towers are built. From initial site selection and design to component manufacturing, transportation, on-site assembly, and even safety control and technical assistance, every step requires the coordinated efforts of a professional team. This is not just a structural engineering project, but a complete system integration project.
As a professional transmission tower manufacturer,JOISYNC has many years of industry experience and is familiar with tower construction solutions for various voltage levels and terrain scenarios. If you are facing planning, design, procurement, or technical implementation issues for a transmission tower project, please contact JOISYNC. We can provide:
- Technical drawing design support
- Tower fabrication and hot-dip galvanizing services
- Installation and construction technical guidance and on-site support
- Dedicated one-on-one project management services
Visit our transmission tower product or submit your request through the on-site form. We will develop a customized transmission tower construction plan to help you complete each tower construction efficiently and safely.