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<=KNEC Diploma in Electrical and Electronics Engineering Module II: Electrical Power Generation, Transmission and Protection past paper July 2016
A two-conductor cable 1000 metres long is required to supply a constant current of Box 414 300 A throughout the year. The cost of cable including installation is Ksh. (1200 a +1200) per metre where 'a' is the cross-sectional area of the conductor in cm2. The cost of electrical energy is Ksh. 10 per kWh. The resistivity of the conductor is 1.73 cm and interest and depreciation charges are 12%. Determine the most economical conductor size.
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Questions List:
1. State three advantages of high power factor
2. Define the following terms with regard to electrical power systems: I. plant factor; II. utilization factor.
3. A 150 MW power station delivers 150 MW for two hours, 50 MW for six hours and is shut down for the rest of the day. It is also shut down for maintenance for 45 days each year. Determine the annual load factor of the station.
4. Explain four reasons for drawing daily load curves for generating stations
5. State two advantages and two disadvantages of a hydroelectric power station
6. With aid of a labelled schematic diagram, describe the operation of a hydro-electric power station
7. Water for a hydroelectric station is obtained from a reservoir with a head of 120 metres. The hydraulic and electrical efficiencies are 0.86 and 0.90 respectively. Determine the electrical energy generated per hour cubic meter of water
8. State three advantages of direct laying of underground cables
9. With aid of diagrams, derive the expression for dielectric stress in a single core underground cable
10. A 33 kV single core cable has a conductor diameter of 10 mm and a sheath of 40 mm. Determine the maximum and minimum stress in the insulation
11. State two types of conductor materials used in electric power transmission lines
12. With aid of a graph, explain Kelvin's law
13. A two-conductor cable 1000 metres long is required to supply a constant current of Box 414 300 A throughout the year. The cost of cable including installation is Ksh. (1200 a +1200) per metre where 'a' is the cross-sectional area of the conductor in cm2. The cost of electrical energy is Ksh. 10 per kWh. The resistivity of the conductor is 1.73 cm and interest and depreciation charges are 12%.
14. List three properties of line supports for overhead line conductors
15. State two functions of excitation systems
16. Draw a labeled block diagram of an excitation system
17. Figure I shows a single line diagram of a three phase system. The percentage reactances of each alternator is based on its own capacity: (i) Determine the short circuit current that will flow into a complete three-phase short circuit at F; ii) Sketch the equivalent reactance diagram.
18. Define the following terms as used in illumination: (a) i) luminous flux; ii) luminous intensity.
19. Two lamps A and B of 100 candela and 200 candela respectively are situated 100 m apart. The height of A above the ground level is 10 m and that of B is 20 m. (i) Sketch the arrangement. (ii) Determine the total illumination at the centre of the line joining the two lamps
20. State two rating factors used to determine the current carrying capacity of a cable
21. State three methods of earthing
22. Draw a labelled construction diagram of high rapturing capacity fuse
23. State two factors which determine whether lighting protection is required
24. With aid of a diagram, explain the cathodic impressed current protection in electrical installations
25. State three hazards regarding electrical installations;
26. State three types of cables used in wiring in division 1 area
27. Describe the IEE regulations for caravan installations
28. Explain the need for each of the following building works in an electrical installation: (i) manhole; (ii) chases.
29. State three precautions to be observed while carrying out each of the services ; manhole and Chases
1. State three advantages of high power factor
2. Define the following terms with regard to electrical power systems: I. plant factor; II. utilization factor.
3. A 150 MW power station delivers 150 MW for two hours, 50 MW for six hours and is shut down for the rest of the day. It is also shut down for maintenance for 45 days each year. Determine the annual load factor of the station.
4. Explain four reasons for drawing daily load curves for generating stations
5. State two advantages and two disadvantages of a hydroelectric power station
6. With aid of a labelled schematic diagram, describe the operation of a hydro-electric power station
7. Water for a hydroelectric station is obtained from a reservoir with a head of 120 metres. The hydraulic and electrical efficiencies are 0.86 and 0.90 respectively. Determine the electrical energy generated per hour cubic meter of water
8. State three advantages of direct laying of underground cables
9. With aid of diagrams, derive the expression for dielectric stress in a single core underground cable
10. A 33 kV single core cable has a conductor diameter of 10 mm and a sheath of 40 mm. Determine the maximum and minimum stress in the insulation
11. State two types of conductor materials used in electric power transmission lines
12. With aid of a graph, explain Kelvin's law
13. A two-conductor cable 1000 metres long is required to supply a constant current of Box 414 300 A throughout the year. The cost of cable including installation is Ksh. (1200 a +1200) per metre where 'a' is the cross-sectional area of the conductor in cm2. The cost of electrical energy is Ksh. 10 per kWh. The resistivity of the conductor is 1.73 cm and interest and depreciation charges are 12%.
14. List three properties of line supports for overhead line conductors
15. State two functions of excitation systems
16. Draw a labeled block diagram of an excitation system
17. Figure I shows a single line diagram of a three phase system. The percentage reactances of each alternator is based on its own capacity: (i) Determine the short circuit current that will flow into a complete three-phase short circuit at F; ii) Sketch the equivalent reactance diagram.
18. Define the following terms as used in illumination: (a) i) luminous flux; ii) luminous intensity.
19. Two lamps A and B of 100 candela and 200 candela respectively are situated 100 m apart. The height of A above the ground level is 10 m and that of B is 20 m. (i) Sketch the arrangement. (ii) Determine the total illumination at the centre of the line joining the two lamps
20. State two rating factors used to determine the current carrying capacity of a cable
21. State three methods of earthing
22. Draw a labelled construction diagram of high rapturing capacity fuse
23. State two factors which determine whether lighting protection is required
24. With aid of a diagram, explain the cathodic impressed current protection in electrical installations
25. State three hazards regarding electrical installations;
26. State three types of cables used in wiring in division 1 area
27. Describe the IEE regulations for caravan installations
28. Explain the need for each of the following building works in an electrical installation: (i) manhole; (ii) chases.
29. State three precautions to be observed while carrying out each of the services ; manhole and Chases
