Question

1- A 69-kV, three-phase short transmission

line is 16 km long. The line has a per

phase series impedance of 0.125 +

j0.4375 ohm per km. Determine the sending

end voltage, voltage regulation, the

sending end power, and the transmission

efficiency when the line delivers

a. 70 MVA, 0.8 lagging power factor at 64 kV

b. 120 MW, unity power factor at 64 kV

2-three-phase, completely transposed 345-kV, 200 km
line has two 795,000-

cmil 26/2 ACSR conductor per bundle and

the following line constants of

z

= 0.032+j0.35 ohm/km and y=j4.2x10-6 S/km.

Full load at the receiving end is 700 MW

at 0.9 pf leading and at 95% of rated

voltage. Determine the following:

a. ABCD parameters of the nominal

π

b. Sending end voltage

Vs, current

IS, and real

power

Ps

c. Percent voltage regulation

d. Transmission-line efficiency at full load.

Answer #1

1- 30-kV, three-phase transmission line has a per
phase series impedance of z = 0.05+j0.45 ohm per Km and a per phase
shunt admittance of y = j3.4x10-6
siemens per km. The line is 80 km long.
Using the nominal π
model, determine
a The transmission line ABCD constants.
b Find the sending end voltage and current,
voltage regulation, the sending end power
and the transmission efficiency when the line
delivers
1. 200 MVA, 0.8 lagging power factor at 220...

A 250 km , three- phase , 50 Hz transmission line is delivering
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line-line) . The conductor resistance is 0.11 ohm/km . The line
inductance per phase is 1.24 mH/km and the line to neutral
capacitance is given as 9.4 x 10 – 9 F/km.
a ) find the nominal – Л representation.
b) find the sending end voltage , VS by nominal – Л...

A 100 km long, three phase 50 hz transmission line has
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receiving end, calculate the regulation and efficiency of the line
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c....

A three-phase 12-mile, 50 kV (line), 60 Hz line has a resistance
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the receiving end of the line absorbs 10 MVA at 90 percent of rated
voltage. Calculate:
ABCD parameters of the line
The sending-end voltage if the load power factor is 0.8
lagging.
The sending-end line voltage, line current and complex power if
the load has a power factor of 0.7 leading.

Use MATLAB:
A three-phase Y-A transformer is rated 225-kV:24-kV, 400 MVA and
has a series reactance of 6.08 Ohms as referred to its high-voltage
terminals. The transformer is supplying a load of 375 MVA, with
0.89 power factor lagging at a voltage of 24 kV (line-to-line) on
its low-voltage side. It is supplied from a feeder whose impedance
is 0.17 + j 2.2 Ohms connected to its high-voltage terminals. The
total load in the system remains constant at 375 MVA....

The generalized circuit constants (ABCD) of a 345 kV
transmission line are given as:
A = D = 0.82 + j0.019
B = 40 +j150 ohm
C = (-1.35 + j193.3) x 10-6 S
Do this problem using the per unit system. Hint: The sending end
power and voltage will make good base values.
a) At the sending end, the transmission line is delivering 400
MVA at 0.8 pf at the rated voltage. Find the receiving end voltage
and current...

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having an impedance per phase of 2 + j5 ?/mile. At the receiving
end of the transmission line is a Y-Y step down transformer T2.
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Load#1 40 MVA at 0.8 pf...

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•...

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• Determine the voltage and power factor at the sending end of
the transmission line.
• Find the parallel capacitor bank in kVAr that enhance the
power factor to unity. Assume the plant voltage is...

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