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<=KNEC Diploma in Electrical and Electronics Engineering Module II: Electrical Power Generation, Transmission and Protection past paper November 2022
A 500 kW steam power generating station uses coal of calorific value 6400 KCal/kg. Thermal efficiency is 40% and electrical efficiency of the station is 92%. Determine the:
(i) overall efficiency of the power station;
(ii) Units generated/ hour,
(iii) Heat produced per hour,
(iv) Coal consumption/hour.
(i) overall efficiency of the power station;
(ii) Units generated/ hour,
(iii) Heat produced per hour,
(iv) Coal consumption/hour.
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Questions List:
1. State two merits of thermal power generation
2. Describe each of the following components of a thermal power station: (i) boiler (ii) economizer, (iii) alternator.
3. Distinguish between impulse and reaction turbines as used in steam power generating plants
4. A 500 kW steam power generating station uses coal of calorific value 6400 KCal/kg. Thermal efficiency is 40% and electrical efficiency of the station is 92%. Determine the: (i) overall efficiency of the power station; (ii) Units generated/ hour, (iii) Heat produced per hour, (iv) Coal consumption/hour.
5. Distinguish between each of the following as used in power generation economics: (i) connected load and peak load; (i) diversity factor and load factor.
6. Figure 1 shows a typical daily load curve for a power station. Draw the corresponding load duration curve.
7. Table 1 shows the daily demands of three consumers Determine the: (i) maximum demand of individual consumers; (ii)diversity factor; (iii) load factor of the station.
8. State three causes of low power factor
9. Describe each of the following methods of improving power factor: (i) static capacitor, (ii)synchronous condenser.
10. Draw a labelled schematic diagram of a brushless excitation system
11. A 100 kW induction motor operating at a power factor of 0.707 lagging and a 50 kW synchronous motor operating at a power factor of 0.9 leading are fed from a single phase supply. Determine the: (i) apparent power for each load; (i) reactive power for each load; (ii) power factor of the combined loads.
12. Explain the functions of each of the following parts of an underground cable. (i) insulation; (ii) bedding. (iii) serving.
13. With the aid of a labelled cross-section diagram, explain the construction of a H-type screened cable
14. A 11 KV single core cable has a conductor cross sectional area of 0.645 cm2 and internal diameter of sheath of 2.18 cm. Determine the: (i) maximum electrostatic stress; (ii) minimum electrostatic stress.
15. State three properties of line supports used in overhead lines.
16. Describe each of the following methods of improving the string efficiency of overhead line suspension insulators: (i) grading insulators; (ii) using a guard ring.
17. With the aid of a labelled diagram, describe the construction of SF circuit breaker
18. A short circuit test on a circuit breaker gave the following readings: -time to reach peak re-striking voltage =50μ sec -peak – re-striking voltage = 100 KV. Determine the: (i) average rate of rise of re-striking voltage (RRRV); (ii) frequency of oscillations.
19. State three merits of using impressed current cathodic protection
20. Explain each of the following requirements on a cathodic protection i)Electrical continuity ii)Electrical isolation iii)Testing equipment
21. With the aid of a schematic circuit diagram, explain the continuous neutral earthing method
22. Outline the procedure of measuring the resistance of the earth continuity conductor
23. Distinguish between each of the following as used in lighting: (i) reduction factor and lamp efficiency (ii) mean spherical candle power and mean hemispherical candle power.
24. State two types of lighting schemes.
25. With the aid of a diagram, describe the construction of a gas filled tungsten filament lamp
26. A room 16 m x 8 m is illuminated by 100 W incandescent lamps of lumen output of 1600 lumens. The average illumination required at the work surface is 300 lux, the utilization factor is 0.5 and the depreciation factor is 1. Determine the number of lamps required
27. Define each of the following terms as used in lighting protection: (i) air terminal; (ii) arrestor; (iii) flash over.
28. Explain three hazards caused by lighting.
29. Outline three IEE regulations concerning lamp holder in an electrical installation
30. Figure 2 shows an installation diagram of a lighting circuit (i) Name the components labelled T1 ,T2 ,T3 and T6 (ii) Draw a wiring installation diagram such that T6 and T5 operate simultaneously and are controlled from three positions.
1. State two merits of thermal power generation
2. Describe each of the following components of a thermal power station: (i) boiler (ii) economizer, (iii) alternator.
3. Distinguish between impulse and reaction turbines as used in steam power generating plants
4. A 500 kW steam power generating station uses coal of calorific value 6400 KCal/kg. Thermal efficiency is 40% and electrical efficiency of the station is 92%. Determine the: (i) overall efficiency of the power station; (ii) Units generated/ hour, (iii) Heat produced per hour, (iv) Coal consumption/hour.
5. Distinguish between each of the following as used in power generation economics: (i) connected load and peak load; (i) diversity factor and load factor.
6. Figure 1 shows a typical daily load curve for a power station. Draw the corresponding load duration curve.
7. Table 1 shows the daily demands of three consumers Determine the: (i) maximum demand of individual consumers; (ii)diversity factor; (iii) load factor of the station.
8. State three causes of low power factor
9. Describe each of the following methods of improving power factor: (i) static capacitor, (ii)synchronous condenser.
10. Draw a labelled schematic diagram of a brushless excitation system
11. A 100 kW induction motor operating at a power factor of 0.707 lagging and a 50 kW synchronous motor operating at a power factor of 0.9 leading are fed from a single phase supply. Determine the: (i) apparent power for each load; (i) reactive power for each load; (ii) power factor of the combined loads.
12. Explain the functions of each of the following parts of an underground cable. (i) insulation; (ii) bedding. (iii) serving.
13. With the aid of a labelled cross-section diagram, explain the construction of a H-type screened cable
14. A 11 KV single core cable has a conductor cross sectional area of 0.645 cm2 and internal diameter of sheath of 2.18 cm. Determine the: (i) maximum electrostatic stress; (ii) minimum electrostatic stress.
15. State three properties of line supports used in overhead lines.
16. Describe each of the following methods of improving the string efficiency of overhead line suspension insulators: (i) grading insulators; (ii) using a guard ring.
17. With the aid of a labelled diagram, describe the construction of SF circuit breaker
18. A short circuit test on a circuit breaker gave the following readings: -time to reach peak re-striking voltage =50μ sec -peak – re-striking voltage = 100 KV. Determine the: (i) average rate of rise of re-striking voltage (RRRV); (ii) frequency of oscillations.
19. State three merits of using impressed current cathodic protection
20. Explain each of the following requirements on a cathodic protection i)Electrical continuity ii)Electrical isolation iii)Testing equipment
21. With the aid of a schematic circuit diagram, explain the continuous neutral earthing method
22. Outline the procedure of measuring the resistance of the earth continuity conductor
23. Distinguish between each of the following as used in lighting: (i) reduction factor and lamp efficiency (ii) mean spherical candle power and mean hemispherical candle power.
24. State two types of lighting schemes.
25. With the aid of a diagram, describe the construction of a gas filled tungsten filament lamp
26. A room 16 m x 8 m is illuminated by 100 W incandescent lamps of lumen output of 1600 lumens. The average illumination required at the work surface is 300 lux, the utilization factor is 0.5 and the depreciation factor is 1. Determine the number of lamps required
27. Define each of the following terms as used in lighting protection: (i) air terminal; (ii) arrestor; (iii) flash over.
28. Explain three hazards caused by lighting.
29. Outline three IEE regulations concerning lamp holder in an electrical installation
30. Figure 2 shows an installation diagram of a lighting circuit (i) Name the components labelled T1 ,T2 ,T3 and T6 (ii) Draw a wiring installation diagram such that T6 and T5 operate simultaneously and are controlled from three positions.
