Pharos University EE-272

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Pharos UniversityEE-272

Electrical Power Engineering 1“Electrical Engineering Dep”

Prepared By:Dr. Sahar Abd El Moneim Moussa

Dr. Sahar Abd El Moneim Moussa

Dr. Sahar Abd El Moneim Moussa 2

OVERHEAD TRANSMISSION LINEMEDIUM OHTL


2- Medium OHTL: ( from 80 km to 240 km)

The medium OHTL can be represented either by:

i. - equivalent circuit ii. T- equivalent circuit


i- - Circuit: Equivalent Circuit:

j X

VS VR

IS R

C/2C/2

Ics I ICR

Ir


The General equation is:

In Matrix Form :

VS = 1+ Z VR

IS = 1+ IR


The ABCD Parameters of a short T.L:

A=D= 1+, B=Z, C=

Efficiency:

x100%

Voltage Regulation:

= x100


i- T- Circuit: Equivalent Circuit:


The General equation is:

In Matrix Form :

VS = 1+ Z VR

IS = 1+ IR


The ABCD Parameters of a short T.L:

A=D= 1+, B= Z, C=

Efficiency:

x100%

Voltage Regulation:

= x100


Example 9A 50 Hz 200 km, transmission line has 132 kV between the lines at the receiving end and has per phase R=0.1 /km , L=0.828 mH/kmAnd C= 0.005 F/km. the line is supplying a load of 30MW at 0.85 lagging pf. Find using approximated -model:

a) A,B,C and D constants of the lineb) V and I at the sending end of the linec) and VR of the line


Solution:Z= R+ j L= 0.1 x 200 + j 2 x x 50 x 0.828 x 10-3 x 200 = 20 + j 52 = 55 69 Y= j C= j 2 x x 50 x 0.005 x 10-6 x 200 = j 314 x 10-6 mho= 314x10-6 90 mhoYZ= -0.016 + j 0.00628 ( 1)

a) A= D= 1

B= Z= 20 + j 52 = 55 69

C= Y = j 314 x 10-6 mho= 314x10-6 90 mho


b) Vs= A VR + B IR = VR + Z IR

VR (ph)= IR= =

Vs= 76210 0 + 55.7 69 x 154 -31.8= 83200 3.6 V

Is= C VR= + DIR= Y VR + I R

= 314 x 10-6 90 x 76210 0 + 154 -31.8= 143 -23.5 A


c) PR= 30 MW

PS = 3 x VSph x Is x Cos S

S= VS - IS= 3.6 –(23.5) = 27.1

PS= 3 x 83200 x 143 x cos 27.1= 31.77 MW

%=

VR% =

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