Code No: II B. Tech II Semester Regular Examinations, April/May 2009 POWER SYSTEMS I. ( Electrical & Electronics Engineering)

Transcription

1 Code No: II B. Tech II Semester Regular Examinations, April/May 2009 SET - 1 POWER SYSTEMS I ( Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer Any FIVE Questions All Questions carry equal marks 1. a) What is meant by water tube boilers and what are the types as well as demerits of water tube Boilers? 8M b) Explain the Economizers in thermal power plants? 8M 2. a) What are the functions of reflections and control rods in a nuclear power plant? 8M b) What are the safety precautions used in Nuclear power stations? 8M 3. a) List out the comparisons of underground verses over head distribution systems? 8M b) A 300m ring distributor has loads as shown in fig, where distances are in meters. The resistance of each conductor is 0.2 per Km and the loads are tapped off at points B, C and D as shown. If the distributor is fed at A at 240v, find voltages at B, C and D. 8M 4. A Single phase line (ABC) of length 2km having resistance and reactance (go and return) as 0.06 and 0.1 /Km. A is the feeding point, B is the mid point of the line taking a load of 100 A at 0.9 p.f leads and C is the far end taking a load of 120 A at unity pf. The voltage at the C is 230v. Find the voltage at the sending end and the phase angle difference between the voltages of two ends, if

2 a) Power factors of the loads are with reference to far end voltage. 8M b) Power factors of the loads are with reference to the voltages at the load points. 8M 5. a) What are the factors to be considered for selecting location of substations. 8M b) Explain the Single bus bar system with sectionalization and what its merits are as well as demerits? 8M 6. a) Why the improvement of power factor is very important for both consumers and generating stations? List the various causes of low power factor and explain? 8M b) A Single Phase motor takes a current of 10A at a p.f of lagging from a 230v, 50Hz supply. What value must a shunting Capacitor have to rise the p.f to Unity? 8M 7. a) Explain clearly how a good load factor and a good diversity factor help to keep overall cost of generation low? 6M b) From a load duration Curve, the following datas are available. The maximum demand on the system is 30MW. The load is supplied by two units one of 20MW and the other of 15MW. Unit No.1 acts as base load unit and No.2 as peak load unit. The base load unit works for 100% of the time and peak load unit for only 45% of the time. The Energy generated by unit No.1 is 1.2 x 10 8 units and that by unit No.2 is 1.1 x 10 7 unit. Determine the load factor, plant capacity factor and plant use factor of each plant. 10M 8. What are the factors influencing tariff design and explain the various types of tariffs in detail? 16M

3 Code No: SET - 2 II B. Tech II Semester Regular Examinations, April/May 2009 POWER SYSTEMS I ( Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer Any FIVE Questions All Questions carry equal marks 1. a) Give the layout of thermal power plant and explain it briefly. (8M) b) What are the essential requirements of thermal power station design? (8M) 2. a) What is Nuclear fusion? How does it differ from Nuclear fission? b) Describe with the help of a neat sketch the construction working of a pressurised water reactor(pwr).what are its advantages and disadvantages. 3. a) Give the comparison between DC and A.C systems of transmission and distribution. (8M) b) Explain about ring main distributor. (8M) 4. a) Explain the voltage drop calculation for the power factors referred to receiving end voltage and with respect to respective load voltages. b) What is voltage drop in A.C distribution? 5. a) What are the considerations for the selection of site for an outdoor substation? (5M ) b) What is a bus-bar? Briefly explain the common arrangement of bus bars (6M ) c) Give the advantages of gas insulated substations. (5M) 6. a) Explain the methods of improving power factor. (8M) b) Describe how the voltage can be controlled for booster transformers. (8M) 7. a) Explain briefly the following i) load curve ii) load duration curve b) A generating station supplies the following loads 15MW ;12MW; 8MW and 0.5MW.

4 The station has a maximum demand of 20MW and the annual load factor is 0.5. Find i)number of units supplied annually ii)diversity factor. (8M) 8. a) What are the objectives and requirements of tariff? b) Explain briefly the following tariff? i) Straight meter rate ii) Block meter rate iii) Do herty rate (Three-Port tariff) (8M)

5 Code No: II B. Tech II Semester Regular Examinations, April/May 2009 SET - 3 POWER SYSTEMS I ( Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer Any FIVE Questions All Questions carry equal marks 1. a) Briefly explain the components of Thermal Power Station. (8) (b) Give the general layout of ash handling and dust collection system?(8) 2. (a) How are Nuclear reactors classified? Explain briefly? (8) (b) Describe with the help of neat sketch the construction working of pressurized water Reactor? (PWR). What are its advantages and disadvantages? (8) 3. (a) Give Comparison between overhead system and underground system? (8) (b) A uniformly loaded distributor is fed at the centre. Show that maximum voltage drop =, where I is the total current fed to the distributor and R is the total resistance of the distributor. A 2 wire D.C distributor 900 meters long is fed at centre and is loaded uniformly at the rate of 1.2 If the resistance of each conductor is 0.04 /Km, find maximum voltage drop in the distributor. (8) 4. A 2- wire A.C feeder 1 km long supplies a load of 100 A at 0.8 p.f. lag 200 volts and its far end and a load of 60 A at 0.9 p.f. lag at its mid-point. The resistance and reactance per km (go and return) are 0.06 and 0.08 respectively. Calculate voltage drop along the distributor from sending end to mid-point and from mid-point to far end. (16) 5. (a) Write short notes on (8) (i) Classification of substations (ii) Indoor sub-stations. (b) Give the comparison between Air insulated substations and Gas insulated substations. 6. (a) Explain the causes of low power factor? (8) (b) Explain how the voltage can be controlled for shunt and series capacitors. (8) (8)

6 7. (a) What is the significance of load curves? (8) (b) Define the following terms (8) (i) Demand factor (ii) Load factor (iii) Utilization factor (iv) Diversity factor. 8. ( a) What do you understand by the term tariff? (8) (b) Explain Flat Rate and Block-Rate tariff s. (8)

7 Code No: II B. Tech II Semester Regular Examinations, April/May 2009 SET - 4 POWER SYSTEMS I ( Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer Any FIVE Questions All Questions carry equal marks 1. Describe the schematic arrangement of a thermal power station and explain the function of each part briefly? (16) 2. (a) Describe the different types of fuels used in a nuclear power plant and discuss the problems of nuclear waste disposal? (10) (b) Discuss briefly the radio active pollution of environment by nuclear power plant? (6) 3. (a) What is meant by radial and loop systems of distribution? Discuss briefly the requirements of a distribution system. (8) (b) A 2- wire DC ring distributor is 300 m long and is fed at 240 v at point A. At point B, 150m froma, a load of 120 A is taken and at C, 100 m in the opposite direction, a load of 80 A is taken if the resistance per 100 m of single conductor is 0.03, find i) Current in each section of distributor ii) Voltage at point B and C (8) 4. A 3 distribution system power is supplied at 11 KV( line voltage) and the balanced load of 50 A/phase at 0.8 lagging p.f and 70 A at 0.9 lagging p.f are taken at Q and R respectively. The impedance of the feeders are PQ=(5+j9), QR=(6+j10), and RP= (4+j8). Calculate the voltage at Q and R and the current in each branch. Power factors are assumed with respect to voltage at P. (16) 5. (a) Explain the main and transfer bus bar system with circuit diagram? (8) (b) What are the merits and demerits of indoor substations over outdoor substations. (8) 6. (a) Why voltage control and power factor correction are necessary in power systems? What are the disadvantages of low voltage and low p.f of the system? (8) (b) A 400 v, 50 cycles, 3 line delivers 207 KW at 0.8 p.f(lag). It is desired to bring the line p.f to unity by installing shunt capacitors. Calculate the capacitance if they are

8 i) Star connected ii) Delta connected (8) 7. (a) Define the following terms (8) i) Plant capacity factor ii) Plant use factor iii) Demand factor iv) Maximum demand. (b) A generating station has the following daily load cycle. Time(hrs) Load (MW) Draw the load curve and find (i) Maximum demand. (ii) Units generated per day (iii) Average load and load factor. 8. (a) Discuss the flat rate and block rate tariff s? (8) (b) What are the factors influencing the tariff design? (8)