PTU B.Tech EEE 3rd Semester May 2019 72165 POWER SYSTEM I Question Papers

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Roll No.

Total No. of Pages : 02

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Total No. of Questions : 09

B.Tech.(EE) PT (Sem.-3)

POWER SYSTEM - I (Transmission & Distribution)

Subject Code : BTEE-405

M.Code : 72165

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Time: 3 Hrs. Max. Marks : 60

INSTRUCTION TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

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SECTION-A

1. Write briefly :
   1. What is skin effect?
   2. 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.
   3. 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.
   4. What are the uses of transposition of power lines?

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   5. State Kelvin's law.
   6. What is meant by surge impedance?
   7. Give a comparison between AC and DC distribution system.
   8. What is meant by capacitance grading of a cable?
   9. What is purpose of using intersheath in a cable?

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   10. What is the use of synchronous phase modifiers?

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SECTION-B

2. 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.

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3. 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.
4. Explain the necessity of a stringing chart for a transmission line and show how such a chart can be constructed?
5. State the classification of cables according to voltage and discuss their general construction.
6. What is void formation in a cable and how does this effect the performance of a cable?

SECTION C

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7. 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.
8. Drive an expression for the capacitance per phase of a three phase line with equilateral and transposed unsymmetrical spacing.
9. 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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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.