Anna University B.E/B.Tech Degree Examination November/December 2010, Seventh Semester, Electrical and Electronics Engineering, EE1402-HIGH VOLTAGE ENGINEERING Answer all the questions. Part-A (10*2=20) 1. What are the causes of over voltage in a power system in few words? 2. Differentiate switching surge from lightning impulse. 3. What is ionization by collision? 4. Define Gas law. 5. Draw the simple voltage doubler circuit. 6. What is Deltatron circuit? 7. What are the advantages of CVT? 8. What are the merits of series resistance micro ammeter method? 9. Define 50% flash over voltage. 10. What are the tests conducted on power transformers? Part-B (5*16=80) 11.(a)(i) What are the causes for switching and power frequency over voltage? How they are controlled in power system? (12) (ii) Explain lightning phenomena. (4) Or 11.(b) What are the different methods employed for lightning protection of over head lines? Discuss in detail. (16) 12.(a) Explain the primary and secondary breakdown mechanism of gaseous dielectrics. (16) Or 12.(b)Explain the various breakdown theories involved in commercial liquid dielectrics. (16) 13.(a) Draw and explain the circuits for producing impulse waves. (16) Page 1

Or 13.(b)Explain any one method of generating HV AC at power frequency and discuss its limitation/feature. (16) 14.(a) Discuss the various techniques for the measurement of impulse voltage. (16) Or 14.(b)With a neat sketch explain the sphere gap measurements for peak voltage measurement. (16) 15.(a) Discuss the various tests carried out in a circuit breaker at HV labs. (16) Or 15. (b) What is the significance of impulse tests? Briefly explain the impulse testing of insulators. (16) Page 2

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011. Sixth Semester Electrical and Electronics Engineering EE 2353 HIGH VOLTAGE ENGINEERING (Regulation 2008) Time : Three hours Maximum : 100 marks Answer ALL questions. PART A (10 2 = 20 marks) 1. What are the causes of over voltages in power system? 2. What is counter poise wire? Give its use. 3. Write the Paschen s law. 4. What are two main reasons for long term break down in composite dielectrics? 5. Give the specifications for standard impulse wave. 6. What are the advantages of cascaded transformer method? 7. What is Rogowski coil? Give its limitations. 8. What are the limitations of series resistance micro ammeter method? 9. What are the tests conducted on surge arrester? 10. What is insulation coordination? PART B (5 16 = 80 marks) 11. (a) (i) Give the origin and characteristics of switching surges and explain the causes of over voltage due to switching surges in EHV and UHV system. (10) (ii) Explain the control measures for over voltage due to switching surge. (6) Or (b) Elaborate the discussion on protection of power system equipments using protective devices. (16) 12. (a) Explain in detail the breakdown mechanism in non-uniform fields and phenomenon of Corona. (16)

Or (b) (i) Describe the ageing and breakdown in composite dielectrics due to partial discharge. (8) (ii) Describe the thermal breakdown mechanism of solid dielectrics. (8) 13. (a) (i) Explain the operation of simple voltage doubler circuit. (4) (ii) Discuss the principle of operation of vande graff generator with neat sketch. (12) Or (b) (i) How the impulse current is generated using capacitor bank. Explain in detail. (8) (ii) Write a brief note on resonant transformer method. (8) 14. (a) Tabulate and explain the methods used for the measurement of high voltages and high currents. (16) Or (b) With neat sketch explain the sphere gap arrangement method of high voltage measurement and give the factors influencing the measurement. (16) 15. (a) Explain the power frequency and impulse voltage test conducted on bushings. Or (b) Discuss the dielectric power factor test and partial discharge test conducted on high voltage cables. (16)

Time : Three hours Reg. No. : B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2011 Sixth Semester Electrical and Electronics Engineering EE 2353 HIGH VOLTAGE ENGINEERING (Regulation 2008) Answer ALL questions PART A (10 2 = 20 marks) 1. What is known as Isokeraunic Level? Maximum : 100 marks 2. A transmission line of surge impedance 250 Ω is connected to a cable of surge impedance 50 Ω at the other end, if a surge of 400 kv travels along the line to the junction point, find the voltage build at the junction. 3. State and explain Paschen s law. 4. What do you mean by Intrinsic strength of a solid dielectric? 5. What are the drawbacks of single stage circuit for the generation of very high impulse voltage? 6. What is a cascaded transformer? Question Paper Code : 11321 7. What is the effect of nearby earthed objects on the measurements using sphere gaps? 8. An electrostatic voltmeter has two parallel plates. The movable plate is 10 cm in diameter. With 8 kv between the plates the pull is 5 10 3 N. Determine the change in capacitance for a movement of 1 mm of movable plate. 9. List out various tests to be carried out on insulator and give a brief account of each test. 10. What are the significances of power factor tests?

PART B (5 16 = 80 marks) 11. (a) (i) An underground cable of inductance 0.150 mh/km and of capacitance 0.2 µf/km is connected to an overhead line having an inductance of 1.2 mh/km and capacitance of 0.006 µf/km. Calculate the transmitted and reflected voltage and current waves at the junction, if a surge of 200 kv travels to the junction, (1) along the cable and (2) along the overhead line. (8) (ii) Describe about various types of shunt protected devices used for overhead lines against lightning stroke. (8) Or (b) (i) Discuss about the various control techniques for switching and power frequency over voltages. (8) (ii) Explain the different theories of charge formation in clouds. (8) 12. (a) (i) Explain clearly various processes which explain electric breakdown in vacuum. (8) (ii) Discuss about the properties of composite dielectrics. (8) Or (b) (i) Explain briefly various theories of breakdown in liquid dielectrics. (10) (ii) Explain the Townsends criterion for a spark. (6) 13. (a) (i) A ten stage Cockraft-Walton circuit has all capacitors of 0.04 µf. The secondary voltage of the supply transformer is 120 kv at a frequency of 150 Hz. If the load current is 1.2 ma, determine (1) voltage regulation (2) the ripple (3) the optimum number of stages for maximum output voltage (4) the maximum output voltage. (8) (ii) Explain the Marx circuit arrangement for multistage impulse generators. How is the basic arrangements modified to accommodate the wave time control resistances? (8) Or (b) (i) Explain the basic principle of operation of an electrostatic generator. (6) (ii) Draw a typical impulse current generator circuit and explain its operation and application. (10) 2 11321

14. (a) (i) Explain with neat diagram how rod gaps can be used for measurement of high voltages. Compare its performance with a sphere gap. (8) (b) (ii) Explain with neat diagram the principle of operation of an Electrostatic Voltmeter. Discuss its advantages and limitations for high voltage measurements. (8) Or A Rogowski coil is required to measure impulse current of 8 ka having rate of change of current of 1010 A/sec. The voltmeter is connected across the integrating circuit which reads 8 volts for full scale deflection. The input to the integrating circuit is from the Rogowski Coil. Determine the mutual inductance of coil, R and C of the integrating circuit. (16) 15. (a) Explain the method of impulse testing of high voltage transformers. What is the procedure adopted for locating the failure? (16) (b) Or Explain the different aspects of insulation design and insulation co-ordination adopted for EHV systems. (16) 3 11321