Power tower: the steel backbone that supports modern electricity
一、The construction process of power towers
The construction of power towers is a complex and intricate project that requires close cooperation between ground and aerial work teams. The ground operation team is responsible for assembling components, which is an important part of the entire construction process. The components of power towers are complex and require extremely high precision, with assembly errors not exceeding 1 millimeter. In order to ensure accuracy, measuring instruments are required during the construction process to accurately measure the inclination angle and height difference of steel pipes.
Ground workers need to strictly follow the design requirements when assembling components. They need to carefully inspect each component to ensure its quality meets the standards. During the assembly process, professional tools and equipment should be used to ensure that the components are firmly and reliably connected.
The high-altitude operation team lifts the assembled components on the ground and installs them in place at high altitude. This is a highly dangerous job that requires operators to have rich experience and professional skills. When conducting high-altitude operations, construction personnel must strictly follow safety operating procedures to ensure their own safety.
There are many high-risk job categories in society, and the traditional industry of power construction is one of the more dangerous types. When facing the high risk of high-altitude operations in power construction, workers must maintain a full mental state and a careful work attitude, ensuring their own safety before conducting scientific high-altitude operations in power construction. So what are the general precautions for high-altitude operations in power construction? Let's take a look together below:
(1) Personnel participating in high-altitude operations in power construction must undergo a physical examination at a formal hospital and pass the physical fitness test before they can carry out the operation.
(2) Any location above 2 meters above the ground is considered high-altitude work, therefore it is necessary to wear relevant safety protection tools.
(3) Before wearing safety protection tools, they should be carefully inspected to ensure that all tools meet quality standards.
(4) Soft soled shoes are required for high-altitude operations during power construction, while hard soled shoes and plastic shoes should be avoided.
(5) The seat belt should be hung on a sturdy and secure component, with the point of force on the upper part of the person's center of gravity.
(6) Before conducting high-altitude operations in power construction, scaffolding should be erected in advance or isolation measures should be taken to prevent falls.
(7) The structure of the springboard on the scaffolding erected at high altitude must be tightly tied to prevent the two ends from curling up.
(8) When working on the top of containers or other dangerous edges such as single steel beams or roofs at high altitude, railings and safety nets should be installed on the side facing the air.
(9) Tools and materials carried during high-altitude operations in power construction should be placed in tool bags and secured with safety ropes. Larger tools should be secured with safety ropes to sturdy components and should not be placed randomly to prevent falling.
(10) High altitude workers are not allowed to throw tools and objects up or down at will.
(11) When conducting high-altitude operations in power construction, if it is not for relevant personnel, other people should be prevented from lingering under the construction site to avoid falling objects and injuring people.
(12) It is prohibited to work on unstable structures, so the structure should be inspected and warning signs hung before construction to prevent accidental boarding.
(13) Attention should be paid to clearing snow during high-altitude power construction in winter, especially in case of icing, to avoid slipping.
The above are the precautions for high-altitude operations in power construction that rely on safety. In recent years, the safety hazards of power construction have become increasingly serious, which is caused by a lack of safety awareness due to non-compliance with safety construction regulations. Therefore, it is recommended that all power construction workers read the above work regulations thoroughly and deeply understand them, in order to avoid terrible power accidents caused by improper operation.
二、Maintenance methods for power towers
1. Steel structure maintenance
• Fire prevention measures: Exposed steel components need to be coated with fire-resistant paint, with a fire resistance time of 1.5 hours for steel beams and 2.5 hours for steel columns, to meet the requirements of building codes.
• Anti corrosion treatment: using sandblasting combined with electric steel brush rust removal process to remove previous rust scales and iron rust. First, apply two coats of epoxy zinc rich anti rust primer, with a dry film thickness of 70um and a practical amount of 0.25-0.3kg/㎡; Apply two more coats of epoxy cloud iron gray thick paste primer, with a wet film thickness of 190um and a dry film thickness of 100um. The weight ratio of paint paste to curing agent is 100:15. After anti-corrosion treatment, the corrosion resistance of the steel structure is significantly improved, which can extend the service life of the power tower and reduce the occurrence of accidents.
2. Remote Maintenance
• Build a remote maintenance system for the iron tower through communication technology, and the on-site data collection end is connected to the local network through Dongyong Technology ORB305 industrial router to monitor and collect relevant data such as signal stability of the iron tower.
• The network transmission end is connected to the data acquisition end through an ORB305 industrial grade wireless router, and a data channel is established between the front-end and the data center through the operator's network to remotely maintain the tower.
• The data center receives transmission data from the front-end through the Dongyong Technology Cloud Platform server for storage, backup, and display. The configuration software is deployed through the Cloud Assistant, and the data can be visually displayed in graphical form for management and maintenance personnel to analyze and process in a unified manner.
3. periodic testing
• Bottom detection: Testing the horizontal angle, ground bolts, nuts, etc. of the power tower, mainly detecting the data of the tower bottom, such as applicability, the quality of the bottom grounding, and whether the anti-theft measures of the foundation bolts are in place. The detection data should be recorded in a timely manner, compared with historical data, analyzed for overall performance, and problems should be rectified in a timely manner. Any problematic components should be replaced in a timely manner.
• Verticality detection: The verticality of the power tower is a key indicator for detection. After detection, the data should be recorded in a timely manner and compared with historical data. If the verticality of the power tower does not meet the relevant requirements, the cause of the error should be identified, an effective rectification plan should be proposed, and the rectification work should be completed within the specified time.
• Component inspection: The power tower is composed of multiple components, and it is necessary to inspect the components on time. To check whether the components of the tower are qualified, obvious deformation, damage, rust, and unqualified parts should be replaced in a timely manner. At the same time, the joints between the components and tower sections should be checked for cracking, especially focusing on key parts such as lightning rods and masts. If there are problems, they should be maintained in a timely manner to ensure their quality and avoid safety hazards caused by component problems.
三、Structural characteristics of power towers
As an important infrastructure for power transmission, the structural characteristics of power towers play a crucial role in ensuring the stability and safety of power transmission.
1. The basic structure consists of three main parts: tower head, tower body, and tower legs. Some iron towers also have cable sections. The members are mainly composed of single equilateral angle steel or composite angle steel, and the materials are generally Q235 and Q345 steel. Q235 and Q345 steel have good strength and toughness, and can withstand various loads borne by power towers. The connection method of angle steel members usually adopts bolt connection, which is convenient for installation and disassembly, and can also ensure the firmness of the connection.
2. Type characteristics
◦ Angle steel towers are generally used in the wild, while steel pipe poles and narrow base steel pipe towers are generally used in urban areas due to their small footprint. Angle steel towers are widely used in fields such as power transmission lines, communication signal transmission, broadcasting and television transmission due to their high strength, stable structure, easy installation and maintenance, and low cost. Angle steel tower is a tower structure mainly composed of angle steel components connected by bolts or welding. It usually adopts a lattice design, that is, multiple angle steel components are assembled in a grid form. This design can increase the rigidity and stability of the tower, while reducing material usage and lowering the tower's own weight.
◦ Steel pipe towers are composed of several circular or polygonal steel pipes, which have advantages such as high strength, high stability, and corrosion resistance. The steel pipe tower structure has relative technological and economic advantages, and is suitable for application in transmission towers that can withstand large loads. Its load characteristics are manifested as low wind pressure borne by the members, high flexural stiffness of the section, simple structure, and clear force transmission, which can fully utilize the bearing capacity of the material. On the one hand, it can reduce the weight of the iron tower and reduce the foundation force; On the other hand, it is beneficial to enhance the ability to resist natural disasters under extreme conditions. By using steel tube towers with relatively small wind pressure shape coefficients while meeting the requirements for strength and stability calculations, the wind load on the tower body can be significantly reduced. In terms of cross-sectional characteristics, the steel pipe components have symmetrical cross-sectional centers and isotropic cross-sectional characteristics; The material is evenly distributed around the perimeter, and the section has high bending stiffness. For the compression bending components of transmission towers, the use of steel pipes with smaller cross-sectional areas and larger turning radii can fully balance the mechanical properties of the material, achieve structural stiffness and stability requirements, especially for large load towers with larger geometric dimensions and longer members. The advantage of good stability performance of steel pipe tower members is obvious. In terms of structural connections, the main materials of the steel pipe tower are connected by flanges or intersecting connections, and the diagonal and main materials are connected by plug-in plates or intersecting connections. The connection structure is relatively simple, which increases the welding workload, reduces the adverse effects of eccentricity of angle steel components on the structural bearing performance, and enhances the stiffness and density of the connection nodes, helping to improve the overall stiffness and stability of the structure and its ability to resist wind-induced dynamic loads.
◦ The steel pipe pole structure is simple, easy to install, and has good corrosion resistance. It is suitable for the installation of medium and low voltage lines, with a small footprint and beautiful appearance. The steel pipe pole is processed and transported separately, assembled on site, and easy to process and install. According to feedback from construction, compared to iron towers, steel pipe poles have the following advantages: they eliminate the need for tower leveling and foundation construction; The tower assembly is convenient, and it takes 2 days to construct and install a self-supporting iron tower, while installing a steel pipe pole only takes 0.5 days. All of these indicate that steel pipe poles have great advantages in facilitating construction and accelerating project progress. At the same time, steel pipe poles occupy a small area, have no cables, require narrow corridors, and are beautiful, upright, and simple, which is more coordinated with the urban environment. However, the processing requirements are high and the cost is high, making them suitable for urban areas. With the increasing awareness of environmental protection among people, relevant departments have put forward higher requirements for environmental protection, and have successively issued a series of relevant regulations to regulate people's behavior, which puts higher demands on the design of environmental protection. Steel pipe poles can meet people's requirements for environmental protection. They adopt mature tower types, have reasonable structures, reliable strength, and fully utilize the mechanical properties of materials. After nearly one year of live operation since the project was put into operation, it has been proven that the pole is safe, reliable, and operates stably.
Steel pipe poles are widely used in urban, suburban, and Senruida transmission line projects due to their advantages of small footprint, no impact on the laying of other pipelines on the foundation, flexible and diverse accessory designs, and less likely to be stolen tower materials. In recent years, the rural power grid renovation project has been steadily advancing, and the number of new construction and renovation projects for power lines has been increasing; At the same time, with the acceleration of urban construction, rapid growth in urban electricity consumption, expansion of municipal road construction, and land development, there are increasing demands for the addition, renovation, and relocation of overhead power lines. Due to limited urban road channels, the application of multi circuit installation is becoming more and more common. Under these conditions, the advantages of urban steel pipe poles in urban power lines are becoming increasingly apparent. In addition, with the application of Q390, Q420, and even higher strength steel materials, steel pipe poles can be designed to be more compact and aesthetically pleasing. But precisely because of the characteristics of steel pipe poles, the amount of steel used for steel pipe poles is relatively large, and their material cost accounts for a much higher proportion in the entire line project than that of self-supporting iron towers.
四、The Development History of Power Towers
1. Historical Tracing
◦ The history of power towers can be traced back to power plants in the late 19th century, when electricity was transmitted in the form of utility poles. With the advancement of technology, people's demands for power transmission are constantly increasing, and power poles are gradually unable to meet the demand, so power towers have emerged.
◦ From early wooden power poles to later reinforced concrete towers, and now to modern steel towers, power towers have been continuously improved and upgraded. For example, there have been three generations of towers for the power transmission across the river in Wufengshan, Zhenjiang, including 110 kV wooden towers, 220 kV reinforced concrete towers, and 500 kV steel towers, witnessing the development of Zhenjiang's power and technological progress.
2. Classification development
◦ According to their shapes, they are divided into five types: wine cup shaped, cat head shaped, top shaped, dry shaped, and barrel shaped. According to their uses, they are divided into tension towers, straight towers, corner towers, etc. Electric power towers of different shapes and purposes play important roles in different scenarios.
◦ In recent years, China's transmission line tower industry has developed rapidly, with continuous growth in sales revenue. With the increasing investment in the power grid, the development prospects are broad. On the one hand, the continuous promotion of ultra-high voltage and 5G construction has brought strong growth momentum to the iron tower industry; On the other hand, there are a large number of Chinese tower production enterprises, presenting a polarized competitive pattern of low-end dispersion and high-end concentration. In the low-end market represented by angle steel towers, there are numerous enterprises, but most of them are small in scale and have weak technical capabilities, resulting in fierce homogeneous competition. In the power tower market with higher voltage levels, due to the high requirements for product safety and stability, State Grid Corporation of China mainly implements a centralized bidding and procurement system. Only large enterprises with large capital scale, reliable product quality, and advanced technology can participate in the competition, and the market concentration is relatively high.
五、The role of power towers
1. An overhead power tower can support the transmission of electricity by raising overhead power lines. As a tower shaped building with a steel frame structure, the power tower usually has a height of 25-40 meters, and one of its main functions is to overhead power lines. By raising the wires high, power towers provide stable support for power transmission, ensuring that electricity can be safely and efficiently delivered to various places.
2. Protect the support to prevent personnel or animals from entering the high-voltage line area by mistake and avoid electric shock accidents. Power towers not only serve as overhead power lines, but also protect the safety of personnel and animals. It can effectively prevent personnel or animals from entering the high-voltage line area by mistake, thereby avoiding the occurrence of electric shock accidents. For example, protective measures such as setting up fences can provide effective protection around the power tower and eliminate safety hazards. At the same time, the substation has also taken a series of measures to prevent small animals, such as sealing cable trenches, doors and windows, setting up rat traps, metal nets, etc., to prevent small animals from entering the distribution facilities and avoid accidents such as short circuits caused by small animals.
3. Different types of power towers have different uses for specific purposes, such as straight towers for hanging vertical insulation ropes in straight sections, and corner towers for line corners. According to different application scenarios, there are multiple types of power towers, each with its specific purpose. For example, the straight tower Z is used for the straight section, hanging vertical insulated ropes; Corner tower J is used for the corners of the line; Terminal tower D places the line terminal in front of the substation; The Cross Tower K is located in a wide river and canyon; Transposition tower H is used for the same phase on the road; The traction tower N is used to limit line accidents and anchor the role of conductors, making it easy to construct and maintain, and to suspend traction insulator chains; Fork tower F is suitable for double circuit front forks; The right angle tower ZJ is used for straight lines at corners. These different types of power towers play their unique roles in the power transmission system.
