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Design of Transmission Tower. Upcoming SlideShare. Like this document? Why not share! Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Published in: Engineering.To browse Academia. Skip to main content. Log In Sign Up. Download Free PDF. Aravind S. The transmission line towers cost about 35 to 45 per cent of the total cost of the transmission line. A transmission tower is a space truss and is an indeterminate structure.
This chapter covers certain basic principles and stipulations to be followed in the analysis and design of transmission line towers, incorporating Indian electricity rulesManual on transmission line towersIS and draft revision of IS The configuration of a transmission line tower depends on the following factors: 1.
The length of the insulator assembly. The minimum clearances to be maintained between conductors, and between conductor and tower. The location of ground wire or wires with respect to the outermost conductor. The mid-span clearance required from consideration of the dynamic behaviour of conductors and lightning protection of the line.
The minimum clearance of the lowest conductor above ground level. The tower configuration is determined essentially by three factors: a Tower height.
Minimum permissible ground clearance hi. Vertical spacing between conductors h3. Vertical clearance between ground wire and top conductor h4. For Extra High Voltage EHV lines, this clause stipulates that the clearance above the ground shall not be less than 5.
The permissible minimum ground clearance for different voltages adopted in India are furnished in Table 3. It should not be less than the values shown in Table 3. For high voltage lines upto and including 11, volts 1. For high voltage above 11, volts and upto and including 33, volts 1. Maximum sag of lower conductor. Height and location of ground wire. Length of cross arm and conductor spacing. Minimum mid-span clearance.
Tower width at base and at top hamper. Span length is fixed from economic consideration.Premium Membership. Study specialized technical articles, electrical guides, and papers. The towers and conductors of a transmission line are familiar elements in our landscape. However, on closer inspection, each transmission line has common components with unique characteristics, beginnings and ends.
In this article, we list main transmission line components and their characteristics:. Transmission towers are the most visible component of the bulk power transmission system. Their function is to keep the high-voltage conductors separated from their surroundings and from each other. Higher voltage lines require greater separation. The unintended transfer of power between a conductor and its surroundings, known as a fault to ground, will occur if an energized line comes into direct contact with the surroundings or comes close enough that an arc can jump the remaining separation.
The first design consideration for transmission towers is to separate the conductors from each other, from the tower, and from other structures in the environment in order to prevent faults. This requirement and the electrical potential voltage define the basic physical dimensions of a tower, including its height, conductor spacing, and length of insulator required to mount the conductor. Given these basic dimensions, the next design requirement is to provide the structural strength necessary to maintain these distances under loading from the weight of the conductors, wind loads, ice loading, seismic loads, and possible impacts.
Of course, the structure must meet these requirements in the most economical possible manner.Transmission Lines - Tower Testing
This has lead to the extensive use of variants on a space frame or truss design, which can provide high strength with minimal material requirements. The result is the ubiquitous lattice work towers seen in all regions of the country.
The last design requirement is to provide a foundation adequate to support the needed tower under the design loads. Some of the environmental implications of a transmission line result directly from these transmission tower design requirements. In addition, excavation, concrete pouring, and pile driving are required to establish foundations. All of these tasks require access roads and service facilities with dimensions and strength sufficient to handle large, heavy tower components, earthmoving equipment, and maintenance equipment.
Figure 1 shows a lattice-type tower with a single-circuit kV line. A close look at the figure reveals twelve conductors strung from insulators suspended on the crossbar, but this is a single-circuit line.
A single-circuit AC line transfers power in three phases. Thus, there are three isolated conductors for a single AC transmission circuit. In addition, some high-capacity circuits at up to kV use multiple bundled conductors for each phase rather than a single larger conductor. The lattice tower in Figure 1 uses groups of four conductors to carry each of the three phases.
Above kV, bundled conductors are normally used to reduce corona discharge. There are several other features to note in Figure 1 above. The conductors are supported in a horizontal configuration. This configuration requires broad towers to achieve adequate line separation, which is about 45 feet between conductors for kV.
The horizontal configuration requires a correspondingly greater cleared width for the ROW than a vertical configuration, which stacks the conductors in a vertical plane.
The vertical configuration results in higher, narrower towers. An alternative to the lattice tower, the monopole toweris also used in this power corridor. The monopole structures shown here actually support two circuits of three conductors each, for a total of six isolated conductors. Just barely visible at the top outer edges of these towers are grounding lines that are connected directly to the towers and that serve as lightning protection.Premium Membership.
Study specialized technical articles, electrical guides, and papers. The foundation is the name given to the system which transfers to the ground the various steady state dead and variable live loads developed by the transmission tower and conductors. Foundations may be variously subjected to compressive or bearing forces, uplift and shear forces, either singly or as a result of any combination of two or three of the forces.
Usually, the limiting design load with transmission line foundations is the uplift load. In this respect, there is a major difference between the design of foundations for transmission lines compared to the design of foundations for most normal civil engineering structures. Accordingly, the amount of literature describing design techniques for overhead line foundations is relatively small compared to the literature available for more traditional civil engineering foundation design practice.
The selected foundation design for a particular tower must provide an economical, reliable support for the life of the line.
The foundation must be compatible with the soil and must not lose strength with age. With the progressive increase in transmission system voltages there has been a related increase in foundation sizes and it is worth noting that with a typical quad conductor kV linesingle leg uplift and ultimate compression loads of 70 or 80 tonnes are usual for suspension towers.
With tension towers, ultimate loads of or tonnes are often developed. With the large sizes of foundations for EHV and UHV transmission it is obvious that significant economies can be made in producing foundation designs to exactly match the soil conditions. Increasingly, transmission lines are routed through areas of poor ground conditionsoften for reasons of amenity. This results in the need for the use of special, generally larger, foundations. The logistical problems of installing large foundations, often in difficult ground conditions, must be taken into account when considering foundation design.
The ground in which the foundations are installed can vary from igneous, sedimentary or metamorphic rock, noncohesive soils, sand or gravel to cohesive soil, usually clays. Equally, soils with a high organic content, for example peat, can also prevail. Composite soils will also be found, and examples of these are sandy gravels and silty sand or sandy peat. Fundamental to the proper design of foundations is an accurate series of soil tests to determine the range of soil types for which the foundation designs will be required.
It is good practice to carry out soil tests at a rate of 1 in 5 tower sites. This is generally sufficient to enable an accurate forecast of the range of soil types to be established.
There are seven basic types of tower foundations:. Resource: High voltage engineering and testing — Hugh M. Ryan Buy this book at Amazon. Designing and esp these foundations vs soil conditions, is possible by group of design engineers working as a joint enterprise. Each tower is a project. So i believe in sharing of knowledge n experience.
And I would like to know how to calculate foundation design? Search for:. More Information. Design of Overhead Transmission Line Foundation. Tower foundation The foundation is the name given to the system which transfers to the ground the various steady state dead and variable live loads developed by the transmission tower and conductors.
In ground of poor load-bearing capacity the dimensions of foundations become considerable.A transmission tower or power tower alternatively electricity pylon or variations is a tall structureusually a steel lattice towerused to support an overhead power line. In electrical gridsthey are generally used to carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations ; utility poles are used to support lower-voltage subtransmission and distribution lines that transport power from substations to electric customers.
They come in a wide variety of shapes and sizes. In addition to steel, other materials may be used, including concrete and wood. There are four major categories of transmission towers:  suspensionterminaltensionand transposition.
Some transmission towers combine these basic functions. Transmission towers and their overhead power lines are often considered to be a form of visual pollution. Methods to reduce the visual effect include undergrounding. The term "pylon" comes from the basic shape of the structure, an obelisk-like structure which tapers toward the top, and the name is mostly used in the United Kingdom and parts of Europe in everyday colloquial speech.
This term is used infrequently in most regions of the United States, as the word "pylon" is commonly used for many other things, mostly for traffic cones. The use of "pylon" is more common in the Midwestincluding areas such as Cincinnati and Chicago. Three-phase electric power systems are used for high voltage or kV and above and extra-high voltage or kV and above; most often or kV and above in contemporary systems AC transmission lines.
In some European countries, e. Germany, Spain or Czech Republic, smaller lattice towers are used for medium voltage above 10 kV transmission lines too.
The towers must be designed to carry three or multiples of three conductors. The towers are usually steel lattices or trusses wooden structures are used in Canada, Germany, and Scandinavia in some cases and the insulators are either glass or porcelain discs or composite insulators using silicone rubber or EPDM rubber material assembled in strings or long rods whose lengths are dependent on the line voltage and environmental conditions. Typically, one or two ground wiresalso called "guard" wires, are placed on top to intercept lightning and harmlessly divert it to ground.
Towers for high- and extra-high voltage are usually designed to carry two or more electric circuits with very rare exceptions, only one circuit for kV and higher. Indeed, for economic reasons, some transmission lines are designed for three or four circuits, but only two or three circuits are initially installed.
Some high voltage circuits are often erected on the same tower as kV lines. Paralleling circuits of kV, kV and kV-lines on the same towers is common. Sometimes, especially with kV circuits, a parallel circuit carries traction lines for railway electrification. High-voltage direct current HVDC transmission lines are either monopolar or bipolar systems.
With bipolar systems, a conductor arrangement with one conductor on each side of the tower is used. On some schemes, the ground conductor is used as electrode line or ground return.
No document with DOI "10.1.1.119.5202"
In this case, it had to be installed with insulators equipped with surge arrestors on the pylons in order to prevent electrochemical corrosion of the pylons. For single-pole HVDC transmission with ground return, towers with only one conductor can be used.
In many cases, however, the towers are designed for later conversion to a two-pole system. In these cases, often conductors on both sides of the tower are installed for mechanical reasons.
Until the second pole is needed, it is either used as electrode line or joined in parallel with the pole in use. In the latter case, the line from the converter station to the earthing grounding electrode is built as underground cable, as overhead line on a separate right of way or by using the ground conductors. Electrode line towers are used in some HVDC schemes to carry the power line from the converter station to the grounding electrode. They are similar to structures used for lines with voltages of 10—30 kV, but normally carry only one or two conductors.
AC transmission towers may be converted to full or mixed HVDC use, to increase power transmission levels at a lower cost than building a new transmission line. Towers used for single-phase AC railway traction lines are similar in construction to those towers used for kV three-phase lines. Steel tube or concrete poles are also often used for these lines.One thing worth noting on this front is that if I had a bet on an event then when logged in I could quickly and easily see the live score of that event on my betslip along with any cash out info.
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