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1st National Certification Exam Energy Auditors 2004 Paper 3

7 pages, 67 questions, 1 questions with responses, 1 total responses,

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Jawaharlal Nehru Technological University (JNTUH), Hyderabad

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Paper EA3 Energy Auditor Set A NATIONAL CERTIFICATION EXAMINATION 2004 FOR ENERGY AUDITORS PAPER EA3: Energy Efficiency in Electrical Utilities Date: 23.05.2004 Timings: 0930-1230 HRS Duration: 3 HRS Max. Marks: 150 General instructions: o o o o o Please check that this question paper contains 7 printed pages Please check that this question paper contains 65 questions The question paper is divided into three sections All questions in all three sections are compulsory All parts of a question should be answered at one place Section I: OBJECTIVE TYPE (i) (ii) (iii) 1. Answer all 50 questions Each question carries one mark Put a ( ) tick mark in the appropriate box in the answer book If the voltage level of the electricity distribution system is raised from 11 kV to 33 kV for the same loading conditions, the distribution losses are reduced by a factor of a) 1/9 2. b) 1/3 b) 1/2 c) 1/3 d) none of the above b) leading power factor d) none of the above Select the location of installing capacitor bank, which will reduce the electricity distribution losses to the maximum extent a) main sub-station bus bars c) motor control centre 5. d) none of the above If the reactive power drawn by a particular load is zero, it means the load is operating at a) lagging power factor c) unity power factor 4. c) 1/6 In electricity distribution, if the voltage is raised from 11 kV to 33 kV for the same loading conditions, the voltage drop in the distribution system would be lower by a factor of a) 1/4 3. Marks: 50 x 1 = 50 b) motor terminals d) distribution board bus bars A pure inductive load draws a) leading reactive power c) lagging reactive power _______________________ Bureau of Energy Efficiency b) active power d) none of the above 1 Paper EA3 Energy Auditor Set A 6. The nearest kVAr compensation required for improving the power factor of a 100 kW load from 0.8 lag to unity power factor is a) 50 kVAr 7. c) 3% d) 4% b) 10 kVAR c) 10.8 kVAR d) none of the above b) 1515 RPM c) 1485 RPM d) none of the above With decrease in design speed of induction motors the required capacitive kVAr for reactive power compensation for the same capacity range will a) increase 11. b) 2% A four pole induction motor operating at 50 Hz, with 1% slip will run at an actual speed of a) 1500 RPM 10. d) none of the above A power factor capacitor designed for 10 kVAR at 415 V was found to be operating at 400 V. The effective capacity of the capacitor would be a) 9.3 kVAR 9. c) 100 kVAr The percentage increase in power consumption of a compressor with suction side air filter pressure drop of 250 mmWC is closest to a) 0.5% 8. b) 75 kVAr b) decrease c) not change d) none of the above kW rating indicated on the name plate of an induction motor indicates a) rated input of the motor b) rated output of the motor c) maximum input power which the motor can draw d) maximum instantaneous input power of the motor 12. For every 4 C reduction in the air inlet temperature of an air compressor, the power consumption will normally decrease by .. percentage points for the same output. a) 1 13. c) 3 d) 4 The acceptable pressure drop in mains header at the farthest point of an industrial compressed air network is a) 0.3 bar 14. b) 2 b) 0.5 bar c) 1.0 bar d) 2 bar PF capacitor installed at the motor starter location will improve a) motor design power factor b) motor operating power factor from the starter to the power supply side c) motor operating power factor from the starter to the motor terminals side d) all of the above. 15. A 200 cfm compressor has a loading and unloading period of 10 seconds and 20 seconds respectively during a compressed air leakage test. The air leakage in the compressed air system would be a) 20.3 cfm 16. b) 42.1 cfm c) 66.6 cfm d) 132.8 cfm Higher chiller COP can be achieved with a) lower evaporator temperature and higher condensing temperature b) lower evaporator temperature and lower condensing temperature c) higher evaporator temperature and higher condensing temperature d) none of the above _______________________ Bureau of Energy Efficiency 2 Paper EA3 Energy Auditor Set A 17. Vertical type reciprocating compressors are used in the capacity range of a) 50 150 cfm c) 500 - 1000 cfm 18. One ton of refrigeration (TR) is equal to a) 3.51 kW 19. b) 3024 kcal/hr b) 2% c) freon b) 0.65 0.70 b) higher c) same b) velocity pressure d) dynamic pressure If the speed of a pump is doubled, pump shaft power goes up by b) 6 times c) 8 times d) 4 times If the speed of a pump is doubled, the pump head goes up by b) 2 times c) 8 times d) 16 times Friction loss in a piping system carrying fluid is proportional to a) fluid flow 28. b) cube of flow rate d) none of the above The outer tube connection of the pitot tube is used to measure in the fan system a) 4 times 27. d) none of the above System resistance in water pumping system varies with a) 2 times 26. d) none of the above Slip ring induction motors, in general, have a design efficiency in comparison with the squirrel cage induction motors for similar ratings a) static pressure c) total pressure 25. d) lithium bromide c) 0.75 0.80 a) square of flow rate c) square root of flow rate 24. d) 4% Li Br water absorption refrigeration systems have a COP in the range of a) lower 23. c) 3% b) pure water a) 0.4 0.5 22. d) all of the above The refrigerant used in vapour absorption systems is a) steam 21. c) 12,000 BTU/hr Approximate percentage reduction in power consumption with 1 C rise in evaporator temperature in refrigerating systems is a) 1% 20. b) 200 500 cfm d) above 1000 cfm b) (fluid flow)2 c) 1 fluid flow d) 1 (fluid flow)2 Shaft power of the motor driving a pump is 30 kW. The motor efficiency is 0.9 and pump efficiency is 0.6. The power transmitted to the water is a) 16.2 kW _______________________ Bureau of Energy Efficiency b) 18.0 kW c) 27.0 kW d) none of the above 3 Paper EA3 Energy Auditor Set A 29. For fans, the relation between flow discharge Q and speed N is Q1 N 1 a) = Q2 N 2 30. b) 4oC d) none of the above c) 5oC d) 7oC Cooling tower effectiveness is a) approach / (range + approach) c) approach / range 32. 3 Q1 N 1 c) = Q2 N 2 3 If inlet and outlet water temperatures of a cooling tower are 40oC and 32oC respectively and atmospheric DBT and WBT are 35 oC and 28 oC respectively then the approach of cooling tower is a) 3oC 31. 2 Q1 N 1 b) = Q2 N 2 2 b) range/ (range + approach) d) none of the above The lowest theoretical temperature to which water can be cooled in a cooling tower is a) DBT of the atmospheric air b) WBT of the atmospheric air c) average DBT and WBT of the atmospheric air d) difference between DBT and WBT of the atmospheric air 33. Which of the following ambient conditions will evaporate maximum amount of water in a cooling tower a) 35 oC DBT and 25 oC WBT c) 35 oC DBT and 28 oC WBT 34. In general, design chilled water temperature drop across chillers is approximately a) 5 oC 35. b) 1 oC b) 12 oC b) luminaire b) HPMV b) general lighting source lamp d) glow light service lamp c) lumens d) none of the above c) HPSV d) LPSV If voltage is reduced from 230 V to 200 V for a fluorescent tube light, it will result in a) reduced power consumption c) increased light levels 40. d) 2.8 oC Luminous efficacy of which of the following is the highest? a) CFL 39. c) 8 oC The unit of illuminance is a) lux 38. d) 15 oC GLS lamp is a) general lighting service lamp c) glow light source lamp 37. c) 10 oC Normally a manufacturer s guaranteed best approach of a cooling tower is a) 5 oC 36. b) 40oC DBT and 38oC WBT d) 38 oC DBT and 37 oC WBT b) increased power consumption d) no change in power consumption and light levels What is the typical frequency of a high frequency electronic ballast? a) 50 Hz _______________________ Bureau of Energy Efficiency b) 10 kHz c) 30 kHz d) 50 kHz 4 Paper EA3 Energy Auditor Set A 41. The compression ratio in diesel engines is in the range of a) 5:1 to 10:1 42. b) 50% 60% b) 5 c) 10 b) 2.2 lakh kCal/hr d) none of the above c) 3.0 lakh kCal/hr d) 3.5 lakh kCal/hr b) inlet air temperature d) all of the above The core losses of a transformer are the least if the core is made up of a) silicon alloyed iron (grain oriented) c) amorphous core metallic glass alloy 47. d) above 70% The operating efficiency of a DG set also depends on a) turbo charger performance c) % loading 46. c) 60% 70% The exhaust gas waste heat recovery potential of a turbo charged genset at 500 kW loading and 480oC exhaust gas is closest to (Assume exit gas temperature of 180oC and 8 kg gas/ kWh generated) a) 1.6 lakh kCal/hr 45. d) none of the above The maximum unbalanced load between phases should not exceed % of the capacity of the DG set a) 1 44. c) 14:1 to 25:1 The rated efficiency of a diesel generator captive power plant has a range of a) 43% 45% 43. b) 10:1 to 13:1 b) copper d) none of the above The basic functions of an electronic ballast fitted to a fluorescent tube light exclude one of the following a) to ignite the lamp b) to stabilize the gas discharge c) to supply power to the lamp at supply frequency d) to supply power to the lamp at very high frequency 48. Modern electronic soft starters are used for motors to a) achieve variable speed c) improve the loading 49. The nearest kVA rating required for a DG set with 1000 kW connected load, with diversity factor of 1.5 and 84% loading and 0.8 power factor is a) 500 kVA c) 1500 kVA 50. b) provide smooth start and stop d) none of the above b) 1000 kVA d) 2000 kVA Maximum demand controller is used to a) switch off non-essential loads in a logical sequence b) switch off essential loads in a logical sequence c) controls the power factor of the plant d) all of the above. . End of Section I . _______________________ Bureau of Energy Efficiency 5 Paper EA3 Energy Auditor Set A Section II: SHORT DESCRIPTIVE QUESTIONS (i) (ii) Marks: 10 x 5 = 50 Answer all Ten questions Each question carries Five marks S-1. Calculate the transformer total losses for an average loading of 60%. Assume no load and full load losses as 3 kW and 25 kW respectively. S-2. (a) What is synchronous speed of an induction motor? (b) How the % slip of an induction motor is measured? S-3. How does power factor of an induction motor reduce with the reduction of the applied load on the motor? Draw a curve depicting power factor vs percentage loading on the motor. S-4. What are the parameters required to be measured while estimating the chiller performance in kW/TR? S-5. A fan is operating at 900 RPM developing a flow of 3000 Nm3/hr. at a static pressure of 600 mmWC. What will be the flow and static pressure if the speed is reduced to 600 RPM. S-6. What are the various methods of flow control in centrifugal pumps? S-7. In a cooling tower, the Cycle of Concentration (C.O.C.) is 3 and evaporation losses are 1%. The circulation rate is 1200 m3 /min. Find out the blow down quantity required for maintaining the desired level of dissolved solids in the cooling water. S-8. Whether it is advisable to install a servo transformer for controlling the operating voltage of the lighting circuit? Justify your answer. S-9. A 5 MW DG set with an average load of 3 MW running in parallel with the grid was found to be exporting 100 kVAr. Without calculating, explain what could be the possible reasons for the export of reactive power to the grid. List advantages/disadvantages of the above situation. S-10. How are energy savings achieved through electronic ballast in a fluorescent tube light in comparison to the conventional magnetic ballast? . End of Section - II . _______________________ Bureau of Energy Efficiency 6 Paper EA3 Energy Auditor Set A Section III: LONG DESCRIPTIVE QUESTIONS (i) (ii) L-1. Marks: 5 x 10 = 50 Answer all Five questions Each question carries Ten marks A plant has 2 identical 500 kVA transformers, each with a no load loss of 0.84 kW and full load copper loss of 5.7 kW. The plant average load is 300 kVA and has never exceeded 450 kVA in the past. (a) Compare the transformer losses when single transformer is in operation and when both transformers are in parallel operation. (b) What would you like to advise to the plant s management on transformer operation keeping in view the energy saving potential, reliability and safety of the system. L-2. A compressed air leakage test was conducted in an engineering industry, which employs a 500 cfm reciprocating compressor. The compressed air system is maintained at the normal loading-unloading settings of 6.5 kg/cm2g and 7 kg/ cm2g respectively. The following was observed for a period of 15 minutes trial: On load time = 40 secs Unload time = 120 secs. Subsequently some of the air leakage points were attended and the leakage test was repeated. The following was observed while maintaining the same loading & unloading pressure settings and trial period: On load time = 20 secs Unload time = 140 secs. The average power drawn during the above 2 trials was observed as 70 kW during load and 15 kW during unload condition. Calculate the annual cost savings for 5000 hr/ year of compressor operation. Assume energy charge of Rs. 5.00 per kWh. L-3. A centrifugal pump is delivering 30 m3/s of water at a discharge pressure of 3 kg/cm2g. The pump suction is 1 meter below the pump center line. Find out the power drawn by the motor if the pump efficiency is 60% and motor efficiency is 92%. L-4. Briefly explain the step by step approach for the conduct of energy audit of vapour compression refrigeration plants. L-5. List 10 energy saving opportunities in a cooling tower. . End of Section III . _______________________ Bureau of Energy Efficiency 7

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