Code No. 2294 / N

FACULTY OF ENGINEERING B.E. 2/4 (EE) II-Semester (New)(Supplementary) Examination, December 2012 Subject : Power System - I Time : 3 Hours

Max. Marks: 75

Note: Answer all questions of Part - A and answer any five questions from Part-B. PART – A (25 Marks) 1. Define the terms: Maximum demand, load factor.

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2. How is the load factor of a sub-station affected by increasing in diversity of loads?

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3. Explain the basic operating principle of ocean thermal energy conversion systems.

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4. Compare flat plate and concentrating type solar collectors.

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5. What are the limitations of solid type cables? How are these overcome in pressure cables? (2) 6. Discuss the advantages and disadvantages of (i) pin-type insulators (ii) suspension type insulators. (3) 7. What are the advantages of bundled conductors?

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8. What do you understand by transposition in overhead lines? Explain why transposition is done in such lines.

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9. Define and explain the terms: feeder, distributor and service mains.

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10. What are the advantages of a doubly fed distributor over singly fed distributor?

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PART – B (5x10=50 Marks) 11.(a) The runoff data of a river at a particular site is tabulated below: Month

January February March April May June

Mean of discharge per month (millions of cum) 45 20 25 10 0 55

Month

July August September October November December

Mean of discharge per month (millions of cum) 85 120 100 60 55 39

(i) Draw a hydrograph and find the mean flow. (ii) Draw the flow duration curve. (iii) Find the power in MW available at mean flow if the head available is 85 m and overall efficiency of generation is 89%. (Take each month of 30 days). (b) Classify the gas turbine power plants.

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(c) What factors should be taken into consideration while selecting the site for steam power plant? (3) 12.(a) What are the advantages and disadvantages of geothermal energy over other energy forms. (b) Describe the principle of a fuel cell and discuss the choice of fuels required. Discuss the advantages of fuel cells.

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Code No. 2294 / N ..2.. 13.(a) The towers of height 40 m and 95 m respectively support a transmission line conductor at water crossing. The horizontal distance between the towers is 520 m. If the tension in the conductor is 1620 kg, find the minimum clearance of the conductor and water and clearance mid-way between supports. Weight of conductor is 1.5 kg/m. Bases of the towers can be considered to be at water level. (5) (b) A single-core 66 kV cable working on 3-phase system has a conductor diameter of 3 cm and a sheath of inside diameter 5.4 cm. If two intersheaths are introduced in such a way that the stress varies between the same maximum and minimum in the three layers, find : (i) positions of intersheaths (ii) voltage on the intersheaths (iii) maximum and minimum stress (5) 14.

Deduce an expression for line to neutral capacitance for a 3-phase overhead transmission line when the conductors are (i) symmetrically placed (ii) unsymmetrically placed but transposed

15.(a) A 2-wire d.c. street mains AB, 650 m long is fed from both ends at 220V. Loads of 20 A, 40 A, 50 A and 30 A are tapped at distance of 100m, 250m, 400m and 500 m from the end A respectively. If the area of X-section of distributor conductor is 1cm2, find the minimum consumer voltage. Take  = 1.7 x 10- 6 cm. (b) Compare the annual cost of power supply to a factory having a maximum demand of 550kW and a load factor of 40% by having the supply from: (i) the factory’s own diesel generating plant (ii) a public supply

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With regards to (i) the capital cost of factory’s own generating plant is Rs.8 lakhs, cost of fuel oil is Rs.210 per ton, fuel consumption 0.65 lbs per kWh. Capital charges, cost of repairs and maintenance, interest and depreciation 15% of the total capital cost. Salaries and wages fo the operating staff are Rs.15,500 per year. With regards to (ii) the tariff is Rs. 160 per kW per annum of maximum demand plus 2.5 paise per kWh. Which of the two alternatives is favourable for the operation of the factory? (5) 16.(a) Two conductors of a d.c. distributor cable AB 1000 m long have a total resistance of 0.1 . The ends A and B are fed at 230 V. The cable is uniformly loaded at 0.5 A per metre length and has concentrated loads of 120A, 60 A, 100 A and 40 A at points distant 200m, 400m, 700m and 900m respectively from the end A. Calculate (i) the point of minimum potential (ii) currents supplied from ends A and B (iii) the value of minimum potential. (5) (b) Find an expression for the flux linkages due to a single current carrying conductor. (5) 17. Write short notes on the following: (a) Three part tariff (b) Radial system (c) Grading of capacitors

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