HIGH VOLTAGE ENGINEERING EE2353 ANNA UNIVERSITY QUESTION PAPER | EE2353 HIGH VOLTAGE ENGINEERING ANNA UNIVERSITY MAY/JUN 2011 QUESTION PAPER
B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 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 is known as Isokeraunic Level?
2. A transmission line of surge impedance 250 is connected to a cable of surge
impedance 50 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?
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)
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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)
(ii) Explain with neat diagram the principle of operation of an
Electrostatic Voltmeter. Discuss its advantages and limitations for
high voltage measurements. (8)
Or
(b) 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)
Or
(b) Explain the different aspects of insulation design and insulation
co-ordination adopted for EHV systems. (16)
