NEA level 7 2075 Question paper

This is the question paper of loksewa aagoy exam 2075 for electrical engineers level 7. 

NEA level 7, Engineer 2075/03/16        

                                                            Section 'A'                                    50 Marks

1. What is an autotransformer? Discuss mertis and demertis of it over a two winding transformer. Also, show that an autotransformer is more useful (copper saving) as compared to a two winding transformer for transformation ratio close to unity. 1+4+5=10

2. What are the types of water turbines used in hydropower? Explain their selection criteria. 4+6=10

3. Draw the connection and explain the operation of differential relay protection of 3-ph, Delta-Star Transformer. A 50 MVA 132/66 kV Wye-Delta transformer is protected by differential protection. Dry connection diagram and calculate suitable CT ratio.            5+5=10

4. Explain clearly the "Ferranti 'effect" with phasor diagram How can you reduce interforence between power and communication line.

5. What do you understand by steady state and transient stability of a three phase synchronous generator operating in synchronism with a power system network? Describe Also, explain the factors that affects its transient stability and the remedial measures that need to be undertaken to improve its transient stability.    5+5=10

                                                            Section 'B'                                                            50 Marks

6. Why the earthing in a sub-station is important? Explain with typical sketch of a 132 kv substation earthing layout. 4+6=10

7. What do you understand by  earthing? Why are electrical equipments and network appliances earthed? Explain the basic requirement of a good effective earthing system.  2+3+5=10

8. Explain the function and the role of a current transformer and a voltage transformer in the instrumentation and protection system of a power system network.                        5+5=10

9. The switch is closed for a long time So that steady state has been reached. At t-o, the switch is opened. Find the voltage and current through inductor as a function of time for to.

10. How digital to Analog Conversion can be achieved by using Weighted-Resistor? What is quantisation error and how can this error be reduced? Explain.                8+2=10

                                                                        The End