PTU Punjab Technical University B-Tech May 2019 Question Papers 3rd Semester Electrical and Electronics Engineering (EEE)-EE-Electrical Engineering
Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(EE) PT (Sem.?3)
POWER SYSTEM - I (Transmission & Distribution)
Subject Code : BTEE-405
M.Code : 72165
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3.
SECTION-C contains T HREE questions carrying T EN marks each and students
have to attempt any T WO questions.
SECTION-A
1. Write briefly :
(a) What is skin effect?
(b) A Conductor consists of seven identical strands each having a radius of r. Determine
the factor by which r should be multiplied to find the self GMD of the conductor.
(c) A load of three impedances each (6+j9) is supplied through a line having an impedance
of (l+j2) ohm. The supply voltage is 400V, 50Hz. Determine the power input & output
when the load is delta connected.
(d) What are the uses of transposition of power lines?
(e) State Kelvin's law.
(f) What is meant by surge impedance?
(g) Give a comparison between AC and DC distribution system.
(h) What is meant by capacitance grading of a cable?
(i) What is purpose of using intersheath in a cable?
(j) What is the use of synchronous phase modifiers?
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SECTION-B
Q2. A three phase 50 Hz transmission line has conductors of factor 90 mm2 and effective
diameter of 1 cm and are placed at the vertices of an equilateral triangle of side lm. The line
is 20 km long & delivers a load of 10 MW at 33 kV and 0.8 power factor. Neglect
capacitance and assume temperature of 20?C. Determine the voltage regulation of line.
Q3. A transmission line conductor at a river crossing is supported between two towers at height
of 50 & 80 m above water level. The horizontal distance between the towers is 300 m. If
the tension in the conductor is 2000 Kg. find the clearance between the conductors and
water at a point midway between the towers. Weight of conductor = 0.844 Kg/m. Assume
that the conductor takes the shape of parabolic curve.
Q4. Explain the necessity of a stringing chart for a transmission line and show how such a chart
can be constructed?
Q5. State the classification of cables according to voltage and discuss their general
construction.
Q6. What is void formation in a cable and how does this effect the performance of a cable?
SECTION-C
Q7. A 50 Hz three phase transmission line is 280 km long. It has total series impedance of
35+j140 ohms and a shunt admittance of 930 mho. It delivers 40 MW at 220 kV at 0.9 pf
lagging. Find the sending end voltage, Voltage regulation, transmission efficiency and A,
B, C, D constants using long line rigorous solution.
Q8. Drive an expression for the capacitance per phase of a three phase line with equilateral and
transposed unsymmetrical spacing.
Q9. A 3 phase transmission line 160 km long transmits a load of 90 MW at 0.8 power factor
Lagging. The line voltage at the receiving end is 230 kV. The constant of the line are as
follows :
A = D = 0.9785 /0.3? B = 85.2 /77.47? C = 0.000503 /90.1?
Construct the receiving end and sending end circle diagrams for the transmission line and
calculate the sending end voltage, current, power factor, regulation and efficiency of the
transmission line.
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
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This post was last modified on 04 November 2019