Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-VI EXAMINATION WINTER 2018
Subject Code:X60903 Date: 27/11/2018
Subject Name: High Voltage Engineering
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1

Compare the different methods for generation of DC high voltage.
07

What are the merits and demerits of generating AC high voltage by resonant transformer method?
07
Q.2

Discuss various factors which affect breakdown of gases.
07

A 12-stage impulse generator has capacitors each rated at 0.35 160 kV. The capacitance of the test specimen is 400 pF. Determine the wave front and wave tail resistances to produce 1.2/50 sec. impulse wave.
07
OR

What is corona discharge? Explain clearly Anode and Cathode coronas.
07
Q.3

Which assumption are made in clump mechanism of breakdown? Also calculate Townsend's primary ionization coefficient α for following case.
In an experiment in a certain gas it was found that the steady current is 5.5×10-8 A at 8 kV at a distance of 0.4 cm between the plane electrodes. Keeping the field constant and reducing the distance to 0.1 cm, results in a current of 5.5×10-9 A.
07

What is the application of insulating oil in different power apparatus? Also explain the testing of transformer oil.
07
OR
Q.3

Explain the breakdown in liquid dielectric by following mechanism.
Cavity breakdown, suspended solid particle mechanism.
07

What do you mean by 'Intrinsic strength' of a solid dielectric? Explain electric breakdown of solid dielectrics by thermal mechanism.
07
Q.4

Enlist different methods for measurement of high voltage. Discuss relative merits and demerits of each.
07

How static and dynamic errors are introduced in digital recorders?
07
OR
Q.4

Explain the application of generating voltmeter for measurement of high voltage.
07

Differentiate between lightning and switching overvoltage. With help of neat sketch define front time and tail time for the impulse wave. Mention allowable tolerances.
07
Q.5

What is the significance of non-destructive testing in high voltage laboratory? Also explain the measurement of large capacitance.
07

Explain the distribution of field lines for different geometry of electrodes in homogeneous, isotropic materials.
07
OR
Q.5

Explain the procedure for calibration of PD detectors in a complete test circuit.
07

Classify the tests conducted on circuit breaker. Explain the use of different components used in short circuit testing laboratory.
07
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