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DESIGN & ANALYSIS OF TRANSMISSION

TOWER

A Synopsis Submitted

in Partial Fulfillment of the Requirements

for the Project of

BACHELOR OF TECHNOLOGY

In

Civil Engineering

By

Abhijit Kumar (Roll No. 1301000001)

Adit Yadav (Roll No. 1301000005)

Amit Tiwari (Roll No. 1301000011)

Ashutosh Yadav (Roll No. 1301000022)

Deepesh Pandey (Roll No. 1301000031)

Under the Supervision of

Mr. B.K Suman

Assistant Professor

United College of Engineering & Research, Naini, Allahabad (U.P)

To

Faculty of Civil Engineering

Dr. A.P.J ABDUL KALAM TECHNICAL UNIVERSITY

LUCKNOW

November, 2016

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Index

S.No Topic Page No.

1. Introduction 3-8

2. Scope of work 9

3. Objective 10

4. Abstract 11-12

5. Methodology 13-15

6. References 16

Figure Index

1. Transmission Tower 3

2. Lattice Tower 4

3. Peak of Tower 5

4. Cross Arm 6

5. Cage 7

6. Tower Body 7

7. Basic Wind Design Map 10

8. Plan of Tower 13

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TRANSMISSION TOWER

INTRODUCTION

A steel transmission tower is a tall structure, usually a steel lattice tower, used to support an

overhead power line. They are used in high voltage AC and DC system, and come in a wide

variety of shape and sizes. Typical height ranges from 15 to 55 m (49 to 180 ft) though the

tallestare the 370 m (1214 ft) span of Zhousman island overhead power line tie.

Fig-1: Transmission tower

In addition to steel other materials may be used, including concrete and wood. The transmission

tower is an important tower accessory and the performance of the transmission line very much

on the design of the transmission tower. The electric transmission tower can be classified several

ways. Here we will try to classify it broadly. The most obvious and visible owe type tower are-

1- Lattice structure

2- Tubular pole structure

Lattice structure

Lattice steel towers are made up of many different steel structural components connected

together with bolts or welded. Many different types of lattice steel towers exist. These towers are

also called self-supporting transmission towers or free-standing towers, due to their ability to

support themselves. These towers are not always made of steel; they can also be made of

aluminum or galvanized steel. Self- supporting lattice structure are used for electricity

transmission line tower. The lattice structure can be erected easily in very inaccessible location

as the tower member can be easily transported. Lattice structure are light and cost effective.

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Tubular steel poles

Tubular steel poles are another of the major types of transmission towers. They are made up of

hollow steel poles. Tubular steel poles can be manufactured as one large piece, or as several small pieces which fit together.

Components of Transmission Tower

Transmission tower consists of following parts

1- Peak of transmission tower

2- Cross arm of transmission tower 3- Boom of transmission tower 4- Cage of transmission tower

5- Transmission tower body

Peak of Transmission Tower

The Peak of transmission tower is mainly used for lay ground wire in suspension clamp and tension clamp in suspension and angle tower locations. Peak is a portion of the above vertical configuration of top cross arm. We can simply say that Peak is the section above the boom in

case of the horizontal section of tower. The peak height depends on the specific angle of shield and clearance of mid span.

Fig- 3: Peak of transmission tower

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Cross arm of Transmission Tower

Cross Arm is one of the key components of transmission line and it holds the power conductor.

Cross arm can vary due to the location and power carried by the transmission line. Number of cross arms depend on the number of circuits consist in Transmission Line.

Fig- 4: cross arm of transmission tower

The Cage

The area between tower body and peak is known as the cage of the Transmission Tower. The

main vertical section of any transmission tower is named as cage. Normally cross section of cage

takes square shape and the shape is also depending on the height of the transmission line.

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Fig- 6: tower body of steel transmission tower

Fig-5: CAGE OF TRANSMISSION TOWER

Body of Tower

Tower body is the main part of the tower which connects the boom and the cage to tower

foundation on body extension or the leg extension. The shape of the body is square type and

tower body consist two columns which connected ate the end of the foundations.

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Advantages of Steel Transmission Tower

There are following advantages of steel transmission tower which are as follows-

This is the major advantage of steel bars, the city is currently under construction, the wave of the

transformation of the city is beautiful and livable if the resident are also more and more attention. Thus urban construction erection of power lines have become increasingly demanding, which is also reflect in their aesthetics requirements, especially in some urban landscape road more

stringent requirements in this regards, while the traditional tower in this regard Is difficult to meet the requirements, steel rod for its compact structure, the image of beautiful compact, so you

can basically meet aesthetic requirements.

Establish the traditional tower construction tower must have a process group, either the whole group or sub group tower, duration are similar but the basic need to set up steel

rod construction process, just the overall steel rod cross arm after installation set immediately available, the construction speed is much faster than the Eiffel tower construction, under normal

circumstances a construction team one day group legislature tower 1.5 to 2 group, and one day steel rod about 10 groups the use of steel rod can greatly improve construction efficiency, shorten the construction period.

Disadvantages of Steel Transmission Tower

The tower material loss has been a major problem plagued the safe operation of the tower,

although taken certain precautions, such as 6 m or less installed anti- theft bolts but the tower loss problems still occurs.

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SCOPE OF WORK

Our primary aim is to design a Transmission Tower proposed tower is situated at Allahabad

which comes into Wind Zone II.

Allahabad falls in the region where wind speed ranges up to 47m/s.

Wind characteristics are as per IS: 875-1987.

Key points and terms involved due to wind forces are:

DESIGN WIND SPEED, DESIGN WIND PRESSURE, and DESIGN WIND FORCE.

We have taken the plan of 4 legged single circuit transmission towers which is widely used as

support to power transmission.

We are using STAAD.ProVi8 for its design and analysis

The member design and code checking in STAAD.PRO are based upon the allowable stress

design method as per two IS: 802 (Part 1/ Sec 1): 1995. It is a method for selecting varying

primary and secondary members under consideration of design loads, allowable stresses and

design limitations.

In this project, the design of steel lattice tower prescribed for transmission of electricity by the

categorized gravity and lateral loads has been studied and analyzed for the employment of the

project. The analysis has been done by taking different combination of loads and then the design

has been come into picture using the code module IS 800:1984.

At all stages, the effort is to provide optimally safe design along with keeping the economic

considerations.

.

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Objective

Main Objective is designing of transmission tower of 132KV current distribution wire

Focus of this project is to propose a steel lattice tower for electricity transmission system and analyze it under various loads thereby designing and checking the proposed members for

failures.

Physical Details - The tower is to be located in the city of Allahabad, Uttar Pradesh. Safe and economic design of steel transmission tower using the software tool STAAD.ProVi8 2008.

The height of the tower is 25 m. The number of cables supported by this tower is 7.

In this Map Allahabad region is shown by green color which shows basic wind speed up to 47

m/s across the year.

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Abstract

In this project Analysis and Design of narrow based Transmission Tower is carried out keeping

in view supplying optimum utilization of electric supply with available resources and increasing population in the locality of Allahabad.

Transmission Line Towers constitute about 28 to 42 percent of the total cost of the Transmission

Lines. The increasing demand for electrical energy can be met more economical by developing different light weight configurations of transmission line towers.

In this project, an attempt has been made to make the transmission line more cost effective keeping in view providing optimum electric supply for the required area by considering unique transmission line tower structure.

The objective of this research is met by choosing a 132KV Self Supporting Lattice Towers with a view to optimize the existing geometry.

Using STAAD PRO v8i analysis and design of tower has been carried out as a three dimensional structure. Then, the tower members are designed.

For the Transmission tower, analysis was performed and the design done for the following loads:

1.Self Weight 2.Wind load and 3.Cable load

India has a large population residing all over the country and the electricity supply need of this

population creates requirement of a large transmission and distribution system. Also, the

disposition of the primary resources for electrical power generation viz., coal, hydro potential is

quite uneven, thus again adding to the transmission requirements. Transmission line is an

integrated system consisting of conductor subsystem, ground wire subsystem and one subsystem

for each category of support structure. Mechanical supports of transmission line represent a

significant portion of the cost of the line and they play an important role in the reliable power

transmission. They are designed and constructed in wide variety of shapes, types, sizes,

configurations and materials. The supporting structure types used in transmission lines generally

fall into one of the three categories: lattice, pole and guyed. The supports of EHV transmission

lines are normally steel lattice towers. The cost of towers constitutes about quarter to half of the

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cost of transmission line and hence optimum tower design will bring in substantial savings. The

selection of an optimum outline together with right type of bracing system contributes to a large

extent in developing an economical design of transmission line tower. The height of tower is

fixed by the user and the structural designer has the task of designing the general configuration

and member and joint details. The goal of every designer is to design the best (optimum)

systems. But, because of the practical restrictions this has been achieved through intuition,

experience and repeated trials, a process that has worked well. Power Grid Corporations of India

Limited has prescribed the following steps to. Optimized the Design of Power Transmission

Lines:-

o Selection of clearances.

o Insulator and insulator string design.

o Bundle conductor studies.

o Tower configuration analysis.

o Tower weight estimation.

o Line cost analysis and span optimization.

o Economic evaluation of line.

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Methodology

The location of transmission tower is in Naini, Allahabad. We are going to design four legged

transmission tower. For the designing of this tower we have to calculate various data as per codal

provision and as per guidelines of governing bodies.

Plan:

The plan on which we are working is four legged single circuit steel transmission tower.

Figure 8: plan of tower

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Method of Work A lattice tower is analyzed as a space truss. Each member of the tower is assumed pin-connected at its joints carrying only axial load and no moment. Today, finite element computer programs

are the typical tools for the analysis of towers for ultimate design loads. In the analytical model the tower geometry is broken down into a discrete number of joints (nodes) and members

(elements). User input consists of nodal coordinates, member end incidences and properties, and the tower loads. For symmetric towers, most programs can generate the complete geometry from a part of the input. Loads applied on the tower are ultimate loads which include overload

capacity factors.

CRITICAL LOAD COMBINATION:

STAAD.Pro does the design on a load case by load case basis. By default, for each load case, the

software carries out design at a total of 13 sections (including start and end) and finds out the

highest utilization ratio amongst all sections for that case. It then moves on to the next case and

follows the same procedure. If the highest utilization ratio for the second case is lesser than that

obtained for the prior one, the former case is retained as critical case and the software moves on

to the next one. If the utilization ratio for the second case being considered is greater than that for

the first one, the second case becomes the new critical load case and it moves on to the next one.

This way it scans through the entire list of cases/combinations and the case/combination with the

highest utilization ratio is reported as the critical load case in the analysis output file along with

the details of the forces at the critical section.

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Data collection and calculation

• As per need of design and analysis.

• Identifying loading condition which is severe. • Analysis and design with the help of Staad pro.

• Validate the data.

Data Input for Design with STAAD.pro

Types of sections of all member groups

ISA Specifications for various angles according to their expected design performance.

Material requirements i.e. concrete in base and Substructure, steeling superstructure.

Load combinations with appropriate factors as per IS-875: 1987-V

Effective length factors for various members

Foundation and soil parameters i.e. moisture content and plasticity etc.

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References

IS CODE 875 Part 3

Limit State Design of Steel Structures by S.K Duggal

Guide for design of steel transmission towers by American Society of Civil

Engineers, American Society of Civil Engineers Task Committee on Tower Design

Design of Latticed Steel Transmission Structures: (ASCE 10-97)

International Journal of Advanced Engineering, Management and Science (IJAEMS)

[Vol-1, Issue-4, July- 2015]