code no: r41022 high voltage engineering · pdf file4 draw the marx circuit arrangement for...
TRANSCRIPT
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IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015
HIGH VOLTAGE ENGINEERING
(Electrical and Electronics Engineering)
Time: 3 hours Max. Marks: 75
Answer any FIVE Questions
All Questions carry equal marks
*****
1 a) Explain how the electric stress can be estimated and controlled. [8]
b) Explain what types of improvements are done for protecting the apparatus from
surge voltages. [7]
2 Explain the process of ionization by collision in gaseous discharge. [15]
3 a) Explain thermal breakdown in solid dielectrics and its significance. [8]
b) A specimen of solid dielectric has a dielectric constant of 5.5, and tan δ = 0.002
at a frequency of 50 Hz. If it is subjected to an alternating field of 55 KV/cm,
calculate the heat generated in the specimen due to the dielectric loss. [7]
4 Draw the Marx circuit arrangement for multistage impulse generators. How is
the basic arrangement modified to accommodate the wave time control
resistances? [15]
5 a) Explain the relative advantages and disadvantages of using a series resistance
micro ammeter and a potential divider with an electrostatic voltmeter for
measuring high d.c. voltages? [10]
b) Explain the conditions to be satisfied by a potential divider to be used for
impulse work? [5]
6 a) Why are the earthing and shielding arrangements needed in the Schering bridge
measurements? [8]
b) Explain the method of balanced detection for locating partial discharges in
electrical equipment. [7]
7 a) Explain the significances of power factor tests and partial discharge tests on
bushings? [8]
b) Explain the importance of Radio interference voltage measurements for EHV
power apparatus. [7]
8 Write short notes on the following:
a) Electrostatic copying
b) Breakdown in composite dielectrics
c) Measurement of DC resistivity [15]
Code No: R41022 Set No. 1 R10
1 of 1
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IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015
HIGH VOLTAGE ENGINEERING
(Electrical and Electronics Engineering)
Time : 3 hours Max. Marks: 75
Answer any FIVE Questions
All Questions carry equal marks
*****
1 a) Explain the importance of air as an insulating material with necessary properties. [8]
b) Explain the effect of transient voltages on the power apparatus.
[7]
2 Explain Photo ionization and secondary ionization processes in gases.
[15]
3 a) Explain the different mechanisms by which breakdown occurs in solid dielectrics
in practice.
[8]
b) Explain the broad classification of insulating materials used in the electrical
equipment and support them with proper examples.
[7]
4 a) With a neat sketch, explain the working of Van de Graff generator and what are
the factors that limit the maximum voltage obtained?
[10]
b) What is a Tesla Coil and explain its significance.
[5]
5
Explain how a sphere gap can be used to measure the peak value of voltages, and
illustrate it with a neat sketch. What are the parameters and factors that influence
such voltage measurement?
[15]
6 a) Define complex permittivity, relative permittivity and loss factor with respect to
lossy dielectric.
[8]
b) Explain the methods used for calibrating the partial discharge detectors.
[7]
7 a) Explain the terms i) Withstand voltage ii) Flash over voltage iii) 50 % flash over
voltage with respect to high voltage testing.
[7]
b) Explain the phenomena of partial discharge tests on high voltage cables.
[8]
8
Write short notes on the following:
a) Electrostatic coating
b) Generation of impulse currents
c) Liquid as an insulator
[15]
Code No: R41022 Set No. 2 R10
1 of 1
www.jntuking.com
www.jntuking.com
www.jntuk
ing.co
m
|''|''|||''|'''|||'|
IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015
HIGH VOLTAGE ENGINEERING
(Electrical and Electronics Engineering)
Time: 3 hours Max. Marks: 75
Answer any FIVE Questions
All Questions carry equal marks
*****
1 a) Explain the electrical field stresses in an insulating material. [8]
b) Explain the Electric field in mixed dielectrics.
[7]
2
Explain Townsend’s current growth equation with proper procedure. [15]
3 a) What is a composite dielectric and further explain its properties. [8]
b) Explain how the temperature and moisture effect the breakdown strength of solid
dielectrics?
[7]
4 a) Derive the expression for ripple and regulation in voltage multiplier circuits. [8]
b) How ripples and regulation can be minimized in voltage multiplier circuits.
[7]
5
Explain the principle of operation of an electrostatic voltmeter for very high
voltages with neat construction. What are its merits and demerits for high voltage
a.c measurements?
[15]
6 a) Explain Mole’s arrangement for measuring high Dissipation factors in the low
frequency range.
[8]
b) Explain how partial discharges in an insulation system or equipment can be
detected and displayed.
[7]
7
Explain the different electrical tests done on isolators and circuit breakers. [15]
8
Write short notes on the following:
a) Electrostatic separator
b) Pure and commercial liquids
c) Applications of insulating materials in rotating machines
[15]
Code No: R41022 Set No. 3 R10
1 of 1
www.jntuking.com
www.jntuking.com
www.jntuk
ing.co
m
|''|''|||''|'''|||'|
IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015
HIGH VOLTAGE ENGINEERING
(Electrical and Electronics Engineering)
Time: 3 hours Max. Marks: 75
Answer any FIVE Questions
All Questions carry equal marks
*****
1 a) Explain the common causes of insulation failure in high voltage cables. [8]
b) Explain the electric field in a single Dielectric medium.
[7]
2 a) What are the factors that influence conduction in pure liquid dielectrics and in
commercial liquid dielectrics?
[8]
b) What is paschen’s law? and explain its importance.
[7]
3 a) How does the internal discharge phenomenon lead to break down in solid
dielectrics?
[8]
b) Explain the different insulating materials used in circuit breakers and cables.
[7]
4
Explain Cockcroft – Walton circuit for voltage multiplier with a neat schematic
diagram.
[15]
5 a) Why are capacitance voltage dividers preferred for high ac voltage
measurements?
[8]
b) What are the requirements of an oscillograph for impulse and high frequency
measurements in high voltage test circuits?
[7]
6
Explain with a neat sketch, the high voltage Schering bridge for the tanδ and
capacitance measurement of insulators or bushings.
[15]
7 a) What is the significance of impulse tests? Briefly explain the impulse testing of
insulators.
[8]
b) Explain why synthetic testing is advantageous over the other testing methods
for short circuit tests?
[7]
8
Write short notes on the following:
a) Electrostatic precipitator
b) Numerical methods for electric field computation.
c) Tripping and control of impulse generators
[15]
Code No: R41022 Set No. 4 R10
1 of 1
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