Elective – III : Electrical Distribution System
Time : Three Hours
Max. Marks : 80
Notes : 1. All questions carry marks as indicated.
2. Solve Question 1 OR Questions No. 2.
3. Solve Question 3 OR Questions No. 4.
4. Solve Question 5 OR Questions No. 6.
5. Solve Question 7 OR Questions No. 8.
6. Solve Question 9 OR Questions No. 10.
7. Solve Question 11 OR Questions No. 12.
8. Assume suitable data whenever necessary.
9. Use of non programmable calculator is permitted.
1. a) Discuss the following terms : [08 M]
i) Diversity Factor
ii) Coincidence Factor
iii) Utilization Factor
iv) Contribution Factor
b) Discuss in detail the classification of loads with their characteristics. [05 M]
2. a) Derive the relation between load factor & loss factor. [06 M]
b) A generating station has a maximum demand of 80 MW and a connected load of 150 MW. If MWhr generated in a year are 400 x 103. Calculate : [07 M]
i) Load Factor
ii) Demand Factor
3. a) Draw a line diagram of a radial type primary feeder. Mention the factors that influence the selection of primary feeders. [06 M]
b) Explain the voltage choice & feeder design for secondary distribution system. [07 M]
4. a) Explain the following : [06 M]
i) Radial type feeders with tie & sectionalising switches.
ii) Radial feeder with express feeder & back feed.
iii) Loop type primary feeder.
b) An industrial area near a city was found to have a load density of 0.5MVA / km2 . The total area was to be located between a rectangular screen of 8km x 4km . Determine the suitable number of 33KV /11KV substation, their capacity & feeder length. The loads are to be served by 11 KV feeders. [07 M]
5. a) Derive the expression for power loss & voltage drop for the feeder line with uniformly decreasing load. [07 M]
b) A 400KV, 3Φ , 4 wire system has balanced loads and is fed from a 11KV / 400V, 3Φ 100KVA transformer. Determine voltage drop, output KVA, KW & pf. of a transformer. The impedances are : [07 M]
section oa =(0.06 + j0.04) Ω
section ab = (0.1 + j0.05) Ω
6. a) What are the different distribution systems for ac & dc? Give comparison. [07 M]
b) For the distribution system shown below, the supply voltage is 240 V. Determine the power loss, KVA, KW & pf at the supply end. [07 M]
7. a) Briefly explain the line drop compensation & voltage control. [06 M]
b) A 33 KV feeder has (0.1 + j0.25)Ω impedance per phase per km and is supplying a load of 6 MVA over a distance of 80 km at 0.75 pf. What will be the receiving end voltage and voltage drop of line if compensated to 50% by series capacitance compensation. [07 M]
8. a) Explain the location of shunt & series capacitors in pf correction. [06 M]
b) An industry has a total induction motor load at 100 hp, efficiency 0.88 and pf 0.8. It is necessary to correct pf to 0.9 lag. Determine the capacitor bank needed. [07 M]
9. a) What is SCADA? How does it help for distribution automation? [07 M]
b) Write a short note on substation automation. [07 M]
10. a) What is earthing? How is it effectively done? What are the methods of reducing earth resistance? . [07 M]
b) Write short note on data acquisition system. . [07 M]
11. a) Explain the various factors to be considered to decide the ideal location of substation. [06 M]
b) Discuss bus arrangement and switching systems in substations. . [07 M]
12. a) What are the different types of faults that can occur on distribution network? Explain them with line diagram. . [06 M]
b) Give the arrangement of a single transformer 11KV / 415V substation & its layout. . [07 M]