GTU B.Tech 2020 Winter Question Papers || Gujarat Technological University
Subject Name: Power System- II
Time: 10:30 AM TO 12:30 PM
Subject Code: 3150911
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE- SEMESTER-V (NEW) EXAMINATION - WINTER 2020Subject Name: Power System- II
Time: 10:30 AM TO 12:30 PM
Instructions:
- Attempt any FOUR questions out of EIGHT questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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| Q.1 | (a) Explain Types of Transmission Line. | 03 |
| (b) Write a short note on (I) Ferranti effect (II) Tuned power lines | 04 | |
| (c) Using Rigorous, Derive expressions for sending end voltage current for long transmission line. | 07 | |
| Q.2 | (a) What is p.u. system? Give the advantages of p.u. system | 03 |
| (b) Explain power in single phase AC circuits briefly | 04 | |
| (c) A synchronous generator is rated 645 MVA, 24 KV, 0.9 pf lagging. It has a synchronous reactance 1.2 O. The generator is feeding full load at 0.9 pf lagging at rated voltage. Calculate: --- Content provided by FirstRanker.com --- (a) Excitation emf (Ef) and power angle d(b) Reactive power drawn by the load Carry out calculations in pu form and convert the result to actual values. | 07 | |
| Q.3 | (a) Give classification of faults. What is difference between steady state reactance Xd, transient reactance Xd’ and sub-transient reactance Xd''? | 03 |
| (b) What is receiving end power circle diagram? Write down steps to draw it. | 04 | |
| (c) Explain factors deciding selection of circuit breaker. | 07 | |
| Q.4 | (a) Explain the performance of loaded Synchronous Machine. | 03 |
| (b) Why does a generator produce only positive sequence voltage? | 04 | |
| (c) A 50 Hz transmission line 300 km long has a total series impedance of 40 + j125 ohms and a total shunt admittance of 10-6 mho. The receiving end load is 50MW at 220 KV with 0.8 lagging pf. Find the sending end voltage, current, power and power factor using nominal - p method. | 07 | |
| Q.5 | (a) What are symmetrical components and its need? | 03 |
| (b) Write and explain symmetrical component transformation | 04 | |
| (c) Using appropriate interconnection of sequence networks, derive the equation for a line to line fault in a power system with fault impedance of Zf. | 07 | |
| Q.6 | (a) Differentiate symmetrical and unsymmetrical faults. List various unsymmetrical faults. | 03 |
| (b) Write equation of phase voltage in terms of symmetrical components | 04 | |
| (c) Explain sequence impedances and networks of synchronous machine. | 07 | |
| Q.7 | (a) | 03 |
| (b) Explain overvoltage due to arcing ground with necessary vector diagram. | 04 | |
| (c) Derive the equation for attenuation of travelling waves | 07 | |
| Q.8 | (a) Write a brief note on capacitance switching. | 03 |
| (b) Give reasons for following: The disruptive critical voltage is less than visual critical voltage. | 04 | |
| (c) Explain travelling waves of a transmission line when the receiving end is short circuited. | 07 |
Date: 29/01/2021
Total Marks: 56
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