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

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?

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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 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.

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