# PTU B.Tech Electrical Engineering 6th Semester May 2019 71135 ELEMENTS OF POWER SYSTEM Question Papers

PTU Punjab Technical University B-Tech May 2019 Question Papers 6th Semester Electrical and Electronics Engineering (EEE)-EE-Electrical Engineering

Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(Electronics & Electrical) (2011 Onwards O.E.)/
(Electrical & Electronics) (2013 OE) (Sem.?6)
ELEMENTS OF POWER SYSTEM
Subject Code : BTEEE-OPC
M.Code : 71135
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 radial distribution network?

(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 (1+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 void formation in a cable?

(j) What is the use of synchronous phase modifiers?
1 | M-71135

(S2)-667

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 having a diameter of 19.5 mm weighs 0.85 kg/m. The span
is 275 m. The wind pressure is 39 kg/m2 of projected area with ice coating of 13mm, the
ultimate strength of the conductor is 8000 kg. Calculate the maximum sag, if the factor of
safety is 2 and ice weighs 910 kg/m3.
Q4. What is a stringing chart? Explain clearly the procedure adopted for stringing the power
conductors on the supports.
Q5. State the classification of cables according to voltage and discuss their general
construction.
Q6. Derive an expression for the capacitance per phase of a three phase line with equilateral
Spacing.
SECTION-C
Q7. A single circuit 50 Hz, 3 phase transmission line has the following parameters /km: R = 0.2
ohm, L = 1.3 mH, C = 0.01F, The voltage at the receiving end is 132 kV. Determine the
efficiency of the line if line is 120 km long and delivers 40 MW at 132kV and 0.8 pf
lagging.
Q8. Derive for a long line the sending end voltage and current relations in terms of receiving
end voltage and current and the parameters of line.
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.

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