Pune University BE Exam Paper High Voltage Engineering

B.E. (Electrical) HIGH VOLTAGE ENGINEERING (2008Pattern) (Elective – III) (Sem. – II)

Time: 3 Hours]                                                                                              [Max. Marks :100

Instructions to the candidates:

1)            Answer 3 questions from Section -1 and 3 questions from Section – II.

2)            Answers to the two sections should be written in separate books.

3)            Neat diagrams must be drawn wherever necessary.

4)            Figures to the right indicate full marks.

5)             You are advised to attempt not more than 6 questions.

6)            Use of logarithmic tables slide rule, Mollier charts, electronic pocket calculator and steam tables is allowed.

7)            Assume suitable data, if necessary.

SECTION – I

Q1) a) Describe in detail Townsend’s theory of breakdown in gaseous medium. What are its limitations.                                                                                                        [12]

b) What is time lag? Why it occurs? What are the different factors which affect on it?       [6]

OR

Q2) a) Differentiate between positive and negative corona discharge. [10]

b) A steady current of 400 micro ampere flows through flat electrodes separated by distance of 5mm when voltage of 10kV is applied. Determine Townsend’s first ionization coefficient. If current of 50 micro ampere flows when distance of separation reduces to 1mm and field is kept constant to previous find Townsend’s secondary ionization coefficient.                                                                                                           [8]

Q3) a) Differentiate between treeing and tracking phenomenon.                                 [8]

b) Describe in detail Intrinsic breakdown in case of solid dielectric material.

[8]

 

Q4) a) What are pure & commercial liquids? How breakdown occurs in Pure liquids?    [8]

b)            Find power law dependence equation from following observation obtained while testing liquid dielectric material.                                                                                  [8]

Gap Distance (cm)

4

6

8

10

Breakdown voltage (kV)

88

135

165

212

 

Q5) a) What are the causes for over voltages?                                                                 [4]

b)            What are the advantages of horn gap arrestor over rod gap.             [4]

c)            Describe any gap type Lightening arrestor.                                          [8]

OR

Q6) a) Write a short note on insulation co-ordination.                                                    [8]

b) Describe in detail Lightening phenomenon.                                   [8]

SECTION – II

Q7) a) With a neat sketch explain Van DeGraff Generator. [8] b) Explain principle of operation of multistage impulse generator and

Describe any one tripping method.                                                                 [8]

OR

Q8) a) Describe cascading transformer. What is its use? State its advantages & Disadvantages over other method.                                                                  [8]

b) A 12 stage impulse generator has capacitor each rated at 0.3 micro farad, 150 kV. The capacitance of the test specimen is 400 pf. Determine the wave front & wave tail resistances to produce a 1.2/50 micro second impulse wave. Also determine the maximum output voltage if the charging voltage is 125 kV.                                         [8]

Q9) a) How sphere gap is used for measurement of high voltage? What are the different factors which affects on measurement? How correction for atmospheric temperature and pressure is applied?                                                                                          [12]

b) Describe any one method of impulse current measurement.                           [6]

 

OR

Describe any one method of Partial discharge measurement.                    [8]

What are the requirements of Cathode Ray Oscilloscopes which are used for measuring impulse voltage and current?                                                                                           [5]

A Schering bridge when used to measure the capacitance and loss angle of the bushing, following observations are obtained Standard condenser = 200 pf, R3 = 4000 Ohm, C3 = 0.00125 micro farad and R4 = 500 Ohm. What are the values of Capacitance and loss factor. [5]

Describe any three tests conducted on insulators.                                        [8]

Write a short note on Design, layout and grounding of HV laboratory.

[8]

OR

Describe any three tests conducted on Bushings.                                         [8]

How power transformer is tested? Which type and Routine tests are conducted on it?     [8]

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