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<=KNEC Diploma in Electrical and Electronics Engineering Module II: Electrical Power Generation, Transmission and Protection past paper November 2016
A substation transformer is supplying 420 kW at 0.6 power factor lagging. The power factor is improved using loss-free capacitors to 0.95 lagging at constant kilowatt.
(i) sketch the phasor diagram;
ii) determine the leading KVAR required
(i) sketch the phasor diagram;
ii) determine the leading KVAR required
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Questions List:
1. State two types of power generating stations in Kenya
2. Describe the following turbines used in power generation: (I) pelton; (II) francis wheel.
3. Explain the operation of a nuclear power station
4. State two types of machine excitation schemes in use
5. Explain the function of the following as used in excitation systems: (I) limiters and protective circuits; (II) d.c. regulator.
6. A generating station has a maximum demand of 20 MW and a load factor of 0.5. Determine the daily energy produced.
7. State three advantages of armoured PVC insulated cables over vulcanized rubber for power distributors.
8. Draw a labelled cross-section diagram of a three core paper insulated lead-sheathed belted cable
9. Outline four causes of low power factor
10. A substation transformer is supplying 420 kW at 0.6 power factor lagging. The power factor is improved using loss-free capacitors to 0.95 lagging at constant kilowatt. (i) sketch the phasor diagram; ii) determine the leading KVAR required
11. State two components in each of the following cost of generating electrical energy: (i) fixed cost; (ii) running cost.
12. Explain how the following factors affect power generation: (i) diversity factor; (ii) load factor.
13. A 415 V, 2-core feeder cable 3 km long supplies a maximum current of 150 A and the demand is such that the copper loss per annum is such as would be produced by the full load current flowing in six months. The resistance of the conductor 1 km long and 1 cm2 cross-sectional area is 0.170 92. The cost of the cable including installation is Ksh (150 A+ 100) per meter where A is the cross-section area
14. State two advantages of suspension type insulator over pin type insulator
15. Describe the following insulator tests: (i) dry flashover, (ii) puncture; (iii) porosity.
16. A string of five insulators is used to suspend one conductor of a 33-kV, three-phase, overhead transmission line. The air capacitance between each cap juction and the earth is one tenth of the capacitance of each unit. Calculate the: (i) voltage across each insulator; (ii) string efficiency.
17. State three advantages of sulphur hexaflouride over air blast circuit breakers
18. Explain the principle of arc extinction in circuit breakers
19. Outline three types of short-circuits in electrical power systems
20. Draw labelled diagrams of the following: (i) cartridge fuse; high-rupturing capacity fuse.
21. With reference to lightning protection, explain how a lightning discharge occurs
22. With the aid of a sketch, explain the term 'zone of protection'
23. State: (i) the basic cause of corrosion (ii) two types of construction materials which cause corrosion
24. With aid of a diagram, describe impressed currents method of cathodic protection
25. Define the following: (i)luminous intensity. (ii) lumen.
26. Draw a labelled diagram of a high pressure mercury vapour lamp.
27. Figure 1 shows two light sources of luminous intensity 120 candela and 240 "candela. Determine the illumination midway between the lamps.
28. Outline five sources of hazards found in agricultural premises
29. Describe the following hazardous areas: (i) division 0; ii) division 1 iii) division 2
30. Differentiate between caravan and superstructure of a building
31. State five types of residential drainage systems
1. State two types of power generating stations in Kenya
2. Describe the following turbines used in power generation: (I) pelton; (II) francis wheel.
3. Explain the operation of a nuclear power station
4. State two types of machine excitation schemes in use
5. Explain the function of the following as used in excitation systems: (I) limiters and protective circuits; (II) d.c. regulator.
6. A generating station has a maximum demand of 20 MW and a load factor of 0.5. Determine the daily energy produced.
7. State three advantages of armoured PVC insulated cables over vulcanized rubber for power distributors.
8. Draw a labelled cross-section diagram of a three core paper insulated lead-sheathed belted cable
9. Outline four causes of low power factor
10. A substation transformer is supplying 420 kW at 0.6 power factor lagging. The power factor is improved using loss-free capacitors to 0.95 lagging at constant kilowatt. (i) sketch the phasor diagram; ii) determine the leading KVAR required
11. State two components in each of the following cost of generating electrical energy: (i) fixed cost; (ii) running cost.
12. Explain how the following factors affect power generation: (i) diversity factor; (ii) load factor.
13. A 415 V, 2-core feeder cable 3 km long supplies a maximum current of 150 A and the demand is such that the copper loss per annum is such as would be produced by the full load current flowing in six months. The resistance of the conductor 1 km long and 1 cm2 cross-sectional area is 0.170 92. The cost of the cable including installation is Ksh (150 A+ 100) per meter where A is the cross-section area
14. State two advantages of suspension type insulator over pin type insulator
15. Describe the following insulator tests: (i) dry flashover, (ii) puncture; (iii) porosity.
16. A string of five insulators is used to suspend one conductor of a 33-kV, three-phase, overhead transmission line. The air capacitance between each cap juction and the earth is one tenth of the capacitance of each unit. Calculate the: (i) voltage across each insulator; (ii) string efficiency.
17. State three advantages of sulphur hexaflouride over air blast circuit breakers
18. Explain the principle of arc extinction in circuit breakers
19. Outline three types of short-circuits in electrical power systems
20. Draw labelled diagrams of the following: (i) cartridge fuse; high-rupturing capacity fuse.
21. With reference to lightning protection, explain how a lightning discharge occurs
22. With the aid of a sketch, explain the term 'zone of protection'
23. State: (i) the basic cause of corrosion (ii) two types of construction materials which cause corrosion
24. With aid of a diagram, describe impressed currents method of cathodic protection
25. Define the following: (i)luminous intensity. (ii) lumen.
26. Draw a labelled diagram of a high pressure mercury vapour lamp.
27. Figure 1 shows two light sources of luminous intensity 120 candela and 240 "candela. Determine the illumination midway between the lamps.
28. Outline five sources of hazards found in agricultural premises
29. Describe the following hazardous areas: (i) division 0; ii) division 1 iii) division 2
30. Differentiate between caravan and superstructure of a building
31. State five types of residential drainage systems
