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EXPT NO:DATE:

COMPUTATION OF TRANSMISSION LINE PARAMETERS

AIM:

To determine the positive sequence line parameters L and C per phase per kilometer of three phase

and doule circuit transmission lines for different conductor arran!ement"

THEORY:

INDUCTANCE

The inductance is computed from flu# linka!e per ampere" $n the case of the three phase lines%

inductance of each phase is not the same if conductors are not spaced equilaterall&" A different inducta

in each phase results in unalanced circuit" Conductors are transposed in order to alance the inductancthe phases and the avera!e inductance per phase is !iven & simple formulae% 'hich depends on condu

confi!uration and conductor radius"

GENERAL FORMULA:

The !eneral formula for computin! inductance per phase in m( per km of a transmission is !iven &

L)*"+ ln,Dm-Ds. ///////////////////////////////////// ,0.

1here Dm)2eometric mean Distance ,23D.

Ds)2eometric 3ean 4adius ,234.

The e#pression for 234 and 23D for different arran!ement of conductors of the transmission lines is

!iven in the follo'in! section"

Three Phase/5&mmetrical 5pacin!:

23D)D ,0"6.

234)r e/0-6)r7,0"8.4)radius of conductor

Three Phase/As&mmetrical Transposed:

23D)2eometric mean of the three distances of the uns&mmetricall& placed conductors

),Da9Dc9Dca. ,0-;.234)re/,0-6.

r)radius of conductor

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234 for t'o su conductor Ds

Ds)sqrt ,Ds9d. /////////////////////////////////////////,+.

,Ds9d;. ,0-6. //////////////////////////////////////////,6.

1here Ds is the 234 of each su conductor and d is the undle spacin!

L)*"+ ln ,23D-234. m(-km /////////////////////////////,8.

Capacitance:

A !eneral formula for evaluatin! capacitance per phase in micro farad per km of a transmission line is !i

&

C) *"*88?-,ln Dm-ln Ds. //////////////////////////////,?.

1here 23D is the @2eometric 3ean Distance 'hich is the same as that defined for inductance under

various cases"

EXERCISES:

0" A three/phase transposed line composed of one AC54 0%6;%*** cmil% 6B-B ; cm and a 234 of ";> cm" The ne' line 'ill also have a flat horiontal confi!uration ut

it is to e operated at a hi!her volta!e and therefore the phase spacin! is increased to 06m as

measured from the centre of the undles" The spacin! et'een the conductors in the undle is68cm"

,a. Determine the inductance and capacitance per phase per kilometer of the aove t'o lines",. =erif& the results usin! the availale pro!ram"

,c. Determine the percenta!e chan!e in the inductance and capacitance in the undle conductor

s&stem" 1hich s&stem is etter and 'h&

+;

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PROGRAM:

FincludeGiostream"hHFincludeGmath"hH

FincludeGconio"hH

void main,.I

clrscr,.J

coutGG P4O24A3 TO K$ND L$NE CON5TANT5GGendlJcoutGG ENTE4 T(E =ALE KO4 5$N2LE CONDCTO4MnGGendlJ

float Da0%D0%Dc0%Dca0%d0%2340%Dm0%Dr0%ll0%cl0%Da%Dc%Dca%d%Ds%l+%c+%234%D%Dm%l%cJ

coutGGENTE4 T(E D$5TANCE

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l+),*"+9+";*;9lo!0*,Dm-Ds..J

c+)*"*88?-,+";*;9lo!0*,Dm-Ds..J

l),,ll0/l+.-ll0.90**Jc),,c+/cl0-c+.90**J

coutGGOTPT =ALE5GGendlJ

coutGGKO4 5$N2LE CONDCTO4GGendlJcoutGGT(E $NDCTANCE $5GGll 0GGm(-kmGGendlJ

coutGGT(E CAPAC$TANCE $5GGcl 0GGnf-mGGendlJ

coutGGKO4

ENTE4 T(E =ALE KO4

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ENTE4 T(E D$5TANCE

ENTE4 T(E >8*m(-km

T(E CAPAC$TANCE $5 *"*000?Bnf-m

KO4 PE4CENTA2E =ALE5

C(AN2E $N $NDCTANCE )+B"8;?>8>C(AN2E $N CAPAC$TANCE )+8"*0;;B

+?

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+" A sin!le circuit three phase transposed transmission line is composed of four AC54

0%+B+%*** cmil conductor per phase 'ith flat horiontal spacin! of 06m et'een phases

a and and et'een phases and c" The undle spacin! is 68m"The conductor diameter is ;"0?m"

,a. Determine the inductance and capacitance per phase per kilometer of the line" ,. =erif& the results usin! availale pro!ram"

PROGRAM:

FincludeGconio"hH

FincludeGiostream"hHFincludeGmath"hH

main ,.

I

clrscr ,.Jfloat Da%Dc%Dca%r%4!m%Deq%Ds%d%Ds 0%aJ

float L%c%L;JcoutGGP4O24A3 KO4 0 C$4C$T 6 AC54 TO K$ND L$NE PA4A3ETE45GGendlJ

coutGG/////////////////////////////////////////////////////////////////////////////////////////////////GGendlJ

coutGG$NPT =ALE5GGendlJ

coutGG///////////////////////GGendlJcoutGGENTE4 T(E D$5TANCE

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L;),*"+60-lo!0*,Deq-Ds..J

c),L;9po',0*%/>..J

coutGGCAPAC$TANCE)GGcGGf-mGGendlJ!etch ,.J

INPUT VALUES:

ENTE4 T(E D$5TANCE 6>?8m

$NDCTANCE)>"**;6+e/*B(-m

CAPAC$TANCE)0"+6?>e/0*f-m

RESULT:

Thus $nductance and Capacitance of transmission line is calculated"

+