Anna University
B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2016
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)
132 132 132
11321 3
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)
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