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DESIGN OF 400KV

TRANSMISSION LINE

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Contents

Abstract

Introduction

The problems associated with EHV-AC

transmission

Pccl substations in Andhra Pradesh

AP Transco 400KV substation

Design of a transmission line

Conclusion

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ABSTRACT:

The transmission lines constitute the electric powersystem. The availability of a well developed high

capacity system of transmission lines makes it

technically and economically feasible to transmit large

blocks of electrical energy over large distances.

At transmission voltages of 132KV,230KV,choice ofconductor size is governed by the current density and

at higher voltages by voltage gradients .

Procedure for the design of 400KV transmission line

is presented ,considering the corona inception, radio

interference level, audible noise, shunt reactorcompensation and switching over voltages.

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INTRODUCTION:

In present day power systems for economical transmission of large blocks

of power over long distances, it is necessary to go for higher and higher

transmission voltages.

As per current terminology, voltages less than 300KV are termed as High

voltage, those between 300KV to 765KV are termed as extra high

voltage(EHV) and those greater than 765 KV are termed as ultra high

voltages(UHV).

In transmission system to choose the high voltage for transmitting a given

amount of power over a given distance economically, the number of factors

to be considered are ;

1.The cost of transmission line

2.Selection of power conductors

3. Tower dimensions

4.Compensatation of reactive power and

5.Cost of active power losses.

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THE PROBLEMS ASSOCIATED WITH EHV ACTRANSMISSION:

1.Corona and radio interference:

Corona is not only a source of power on transmission lines but also asource of interference with radio and communications. The problem is moreacute when transmission of power is at EHV.

Bundled conductors offer an economical solution for minimizingcorona loss and radio interference for EHV lines.

2.Line support:EHV lines have large mechanical loading on towers due to bundied

conductors, large air and ground clearances.

The transmission line must therefore, be made more wind resistance.

3.Insulation Requirement:

The magnitude of likely voltage surges determines the required lineinsulation level.

In addition the recent trend is to go for HVDC transmission fortransfer of bulk amount of power over long distance.

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Pccl substations in Andhra Pradesh

Ramagundam switching station(RSS)

Ganapoor(HYD)

Nagarjunsagar (Thallapally)

Guthi(Ananthapoor)

Kadapa

Khammam

Ramagundam switching station is undercontrol ofNTPC

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AP Transco 400KV Substations

Mamidipally

Kurnool

Vizag(Kalapaka)

Rajahmandri(Vemagiri)

Chittoor

Nellore

Mahbhoob Nagar

Dichpally(NZB)

Gajwel

All this substations are inter connect with

PCCL lines

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DESIGN OF A TRANSMISSION LINE:

The necessary electrical design features are:

1.Choice of voltage

2.Selection of conductors

3.Spacing of conductors

4.Corona

5.Insulation design

6.Surge impedance loading of transmission line.

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The necessary mechanical design features are:

1.Loading on transmission conductors

2.Span,sag and Tension

3.Sag-Tension relation

4.Effect of temperature

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Transmission line designTransmission line design

The electric lines thatgenerate the most publicinterest are high-voltagetransmission lines.

These are the largest and

most visible electric lines.Most large cities requireseveral transmission linesfor reliable electric service.

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Conclusion

The silent features of a EHV transmission line are presented

in this work. The Electrical and Mechanical Design aspects of

a 400KV Line are presented.

The effect of choice of voltage for transmission and the

performance of the line are discussed.

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References

o Power system analysis and design

------ B.R. Gupta

o Electrical power systems

------ V.KMehtha

o Google

o Wikipedia