EE3113 Power System Analysis [617220]

EE3113 Power System Analysis
Dr. Umer Amir KhanTransmission LinesSection # 02

1. Introduction
•Transmission lines are the back bone of the electric power system

1. Introduction
•Our objective is to be able to model a transmission line.

1. Introduction
ResistanceInductance
Capacitance
Conductance

2. Critical Parameters -Resistance
•Resistance is the opposition to the flow of electrons.
•All transmission lines have natural resistance.
•They generate power losses (copper losses).
•A critical parameter used in modeling of transmission line.
PR=i2R

2. Critical Parameters -Inductance
•A flowing current generates a magnetic field around the conductor.
•This magnetic field will generate self inductance as well as mutual
inductance between other lines

2. Critical Parameters -Inductance

2. Critical Parameters -Inductance
dtdN eind

2. Critical Parameters -Capacitance

2. Critical Parameters -Capacitance

2. Critical Parameters -Conductance

2. Critical Parameters -Conductance

2. Critical Parameters
Series Impedance (Z) Resistant, Inductance
Shunt Admittance (Y) Capacitance

3. Representation of Lines

3. Representation of Lines
•Transmission line modeling is based on the length of the
transmission line.
•There are three types of transmission line models
•The short Transmission Line (length < 80 km)
•The Medium Transmission Line (Length >80 km & < 240 km)
•The Long Transmission Line (Length > 240 km)

4. The Short Transmission Line

4. The Short Transmission Line

4. The Short Transmission Line

4. The Short Transmission Line

5. The Medium Transmission Line
•Transmission line modeling is based on the length of the
transmission line.
•There are three types of transmission line models
•The short Transmission Line (length < 80 km)
•The Medium Transmission Line (Length >80 km & < 240
km)
•The Long Transmission Line (Length > 240 km)

5. The Medium Transmission Line

5. The Medium Transmission Line

5. The Medium Transmission Line

5. The Medium Transmission Line

5. The Medium Transmission Line

5. The Medium Transmission Line

6. The Long Transmission Line
•Transmission line modeling is based on the length of the
transmission line.
•There are three types of transmission line models
•The short Transmission Line (length < 80 km)
•The Medium Transmission Line (Length >80 km & < 240 km)
•The Long Transmission Line (Length > 240 km)

6. The Long Transmission Line

6. The Long Transmission Line

6. The Long Transmission Line

4. The Short Transmission Line

4. The Short Transmission Line

4. The Short Transmission Line

4. The Short Transmission Line

QUESTION
A 220-kV, 150 MV A, 60 -Hz, three -phase transmission line is 140 km long. The
characteristic parameters of the transmission line are:
r = 0.12 Ω/km; x = 0.88 Ω/km; y =4.1 ×10-6 S/km
where, r is the resistance per kilometer, x is the reactance per kilometer, y is the shunt
admittance per kilometer.
The voltage at the receiving end of the transmission line is 210 kV. will treat it as short
line:
a) What is series impedance and shunt impedance of the transmission line ? Draw the
equivalent circuit of the transmission line?
b) Solving the transmission line as short transmission line, what is the sending end
voltage if the line is supplying rated voltage and apparent
power at 0.85 PF lagging? At unity PF? At 0.85 PF leading?
c) What is the voltage regulation of the transmission line for each of the cases in (b)?
d) What is the efficiency of the transmission line when it is supplying rated apparent
power at 0.85 PF lagging?