The total capacitance of the transmission line is considered at the
receiving end side or load side in the medium transmission line. All the
parameters are given considering three phase transmission line.
Here
VS =
Sending end voltage to neutral
VR = Receiving end voltage to neutral
IS = Sending
end current
IR =
Receiving end current
IC =
Capacitance current
R = Resistance of
transmission line, resistance to the neutral in the three-phase line
X = Reactance of
transmission line, reactance to the neutral in the three-phase line
Z = R + j X =
Impedance
Y = jXC
= Admittance
A, B, C and D =
Constant
Generalized
Constant of the transmission line is given by sending end voltage and sending
end current equation
VS = AVR
+ BIR……. ( 1 )
IS = CVR
+ DIR……....( 2 )
Important Points to be noted
The sending end current is equal to receiving end current and capacitor current in the end condenser medium transmission line.
IS = IR
+ IC
IS = IR
+ YVR
IS = YVR
+ IR …… ( 3 )
Similarly
Vs = VR
+ ISZ
= VR + ( IR + YVR
)Z
= VR + ZIR + ZYVR
= ( 1 + YZ )VR + ZIR ….. ( 4 )
Compare equation (
2 ) and ( 3 )
IS = CVR + DIR |
IS = YVR + IR |
C = Y and D = 1 |
Compare equation ( 1 ) and ( 4 )
VS = AVR + BIR |
Vs = ( 1 + YZ )VR + ZIR |
A = ( 1 + YZ ) and B = Z |
From the above
value of A,B,C and D
A = ( 1 + YZ )
B = Z
C = Y
D = 1
Therefore
AD – BC = 1
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