CEB Past Papers.pdf

EXAMINATION FOR THE RECUREMENT OF ELECTRICAL SUPERINTENDENTDS FOR CEYLON ELECTRICAL BOARD Time – 1.5 hours 9th November 1996 1) Give four reasons for the recent ‘Power Crises’ that occurred in Sri Lanka. 2) What are the methods available for the control of speed of an induction motor? 3) What is meant by ‘Maximum Demand’ and explain how it is measured? (The explanation should give the principle behind the measurement) 4) Why is three phase power preferable to other systems? 5) Explain the steps that you would take before disconnecting an ammeter permanently supplied from a current transformer. Give reasons. 6) Why are high voltage used in transmission of electricity? 7) What the method is as specified in the IEE wiring regulations that is used for earthing distribution systems in Sri Lanka? 8) What are the different types of of prime moves moves available in thermal power generation? 9) What are the renewable energy sources available for power generation other than hydro power? 10) How does one control the active power, reactive power and terminal voltage at a generator which is feeding into power systems? 11) What are the types of turbines used in hydro power stations? Indicate the conditions under which each type of turbine is more suitable. 12) Specify all necessary conditions to synchronize a generator to a power system. 13) W hat is ‘differential protection’? Explain in relation to its application to a generator - transformer unit. 14) Specify six size/types of conductors used in transmission lines, indicating the codes used to denotes each size/type. 15) What are the instrument transformers? Briefly explain their uses. 16) What are the types of protection generally used for a power transformer having capacity of about 5 MVA? What is the basis principle (behind each of the types of protection listed) 17) What are the types of losses that occur in a power transformer? What advantages do such conductors offer in electricity distribution? 18) What is meant by ‘time of day tariff’ and why is such a tariff necessary? 19) What are aerial bundled conductors? What are the advantages do such conductors offer in electrical distribution? 20) How would you distinguish between a ‘transmission line’ and a distribution line? 21) Specify six of the cooling methods employed for power transformers. Indicate the notation used for each type. 22) What are the conditions to be satisfied before two three phase transformers can be made to operate in  parallel? 23) What are the control signals used in an AVR? 24) Give the sketch of the circuit of an electronic fan regulator and label it 25) Give the input/output input/output voltage relationship for; a. Bridge rectifier  b. Half-wave rectifier 26) What is the function of a UPS and indicate its ty pes and ratings.

2006 Electrical Supernatant Entrance Exam Paper Answer all questions. Time : 1½ hours. 1) What are the losses in a transformer? Explain how these losses are determined? 2) What are the causes of low power factor? Explain the disadvantages having poor power factor. How is the power factor improvement achieved in industry? 3) Name three conventional and three non‐conventional sources of energy that can be used for power generation. 4) On what basis turbines used for hydropower generation are classified? What are the turbines used for hydropower generation according to classification based on water head? 5) Draw a typical layout of a gas turbine plant and name the main components of it. 6) Define the terms, the load factor and diversity factor and discuss the effects of these factors on the cost of  generation of electrical energy. 7) Explain briefly why the unit cost of electricity is high in Sri Llanka. How it will be reduced when the proposed upper Kotmale and Norochcholai power plants are commissioned? 8) How the voltage and frequency of an interconnected power system are controlled? 9) Explain with the circuit diagram, the operation of differential protection scheme used to protect a Delta/Star transformer. 10) What are the conditions that should be satisfied for parallel operation of two transformers with same ratings? 11) What do you understand by primary and back‐up protection? What will happen when a secondary of current transformer is opened while primary is energized? 12) What is voltage sag (Dip)? What are the parameters used to define voltage sag (Dip)? 13) Explain basic mechanism of voltage harmonic distortion in the power system. 14) Name two sources which inject harmonics to power system. What are effects of harmonics distortion in the power system? 15) Explain operating principal of (1) Auto Reclocer 16) Compare the disadvantages and disadvantages of Arial Bundle Conductors over Aluminum bare conductor in a distribution line. 17) As demand side management, what type of measures could be taken to save electrical energy? 18) Explain why the distribution planning is necessary to strengthen distribution network. 19) Why does the voltage of shunt generator drop as load is applied to its terminals? 20) Name five applications of DC shunt motors based on characteristics like speed and torque. 21) What are the differential methods of speed control of three phase induction motors? 22) What do you understand by optimal feeding point of a distribution feeder? Give two methods that could be used to improve the voltage of a distribution feeder. 23) What is meant by “Time of day tariff” Explain how time of day tariff could improve the system load factor. 24) Draw a circuit diagram of a computer power supply and explain its operation. 25) What is UPS? Explain its operation with the help of a block diagram or a circuit diagram.