JNTU previous papers B Tech IInd Sem Examinations, High voltage engineering, Apr/May 2008

JNTU previous papers

JNTU B.Tech II Semester Examinations, HIGH VOLTAGE ENGINEERING, Apr/May 2008

(Electrical & Electronic Engineering)

Time: 3 hours Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

SET-I

1. (a) How is the electric field intensity/ electric stress controlled?

(b) Explain about uniform and non-uniform electric fields. [8+8]

 

2. Explain in detail about thermal breakdown mechanism in commercial liquids. [16]

 

3. Explain the breakdown mechanism in composite dielectrics due to aging and partial

discharges. [16]

 

4. (a) How are the wave front and wave tail times controlled in impulse generator circuits.

(b) An impulse generator has eight stages with each condenser rated for 0.16 ?F and 125 kV. The load capacitor available is 100 pF. Find the series Resistance and damping Resistance needed to produce 1.2/50 ?s impulse wave. What is the maximum output voltage of the generator, if the charging voltage is 120kV? [8+8]

 

5. (a) What are the advantages and disadvantages of an electrostatic voltmeter when

used to measure high voltages.

(b) What is a mixed potential divider? How is it used for impulse voltage measurements. [8+8]

 

6. Give the mathematical models for lightning discharges and explain them. [16]

 

7. Explain the operation of high voltage Schering bridge when the test specimen

(a) is grounded

(b) has high loss factor? [8+8]

 

8. What is an operating duty cycle test on a surge arrester? Why is it more significant

than other tests? [16]

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