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High%20Voltage%20Engineering 1
Course: Electrical engineering (EET301)
121 Documents
Students shared 121 documents in this course
University: Rashtrasant Tukadoji Maharaj Nagpur University
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NRJ/KW/17/4604 1 P.T.O
B.E. (Electrical (Electronics & Power) Engineering) Seventh Semester (C.B.S.)
High Voltage Engineering
P. Pages : 2 NRJ/KW/17/4604
Time : Three Hours Max. Marks : 80
________________________________________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Notes : 1. All questions carry marks as indicated.
2. Solve Question 1 OR Questions No. 2.
3. Solve Question 3 OR Questions No. 4.
4. Solve Question 5 OR Questions No. 6.
5. Solve Question 7 OR Questions No. 8.
6. Solve Question 9 OR Questions No. 10.
7. Solve Question 11 OR Questions No. 12.
8. Due credit will be given to neatness and adequate dimensions.
9. Assume suitable data whenever necessary.
10. Illustrate your answers whenever necessary with the help of neat sketches.
11. Use of non programmable calculator is permitted.
1.
a)
Write short note on "Streamer theory of Breakdown in gases.
7
b)
In an experiment it was found that, the steady current is 5.2x10-8 Amp at 7.5 kV at a distance
of 35 mm between the plane electrodes. Keeping the field constant and reducing the distance
to 0.1cm results in a current of 5.2x10-9 Amp. Calculate the primary ionization coefficient
''
.
6
OR
2.
a)
Write short note on: 'Mechanism of vacuum breakdown'
7
b)
A solid dielectric specimen of dielectric constant
r
= 3, has internal void of thickness
1.5mm. The specimen is 1.0cm thick and it is subjected to a voltage of 80 kV (RMS). If
void is filled with air and breakdown strength of air is 30 kV (Peak/cm). Find voltage of
internal discharge.
6
3.
a)
Explain classification of Lightning strokes according to their effect on power system.
6
b)
A transmission line tower has a resistance of 15
and inductance 30 mH. Compute the
surge voltage to which tower top is subjected if Lightning stroke current is 35 kA. Compute
the percentage reduction in overvoltage if tower resistance is reduced to 5
. Draw the
equivalent circuit to explain the above phenomenon and waveform of lightning stroke.
8
OR
4.
a)
Explain clearly how the rating of L. A. is selected. What is best location of L.A. and why?
6
b)
What are the causes for switching & power frequency over voltages & how they are
controlled in power system?
8
5.
a)
Explain the behavior of travelling waves with a voltage & current waveform of open
ended transmission line.
7
b)
A long tailed unit function 500 kV surge voltage on an overhead transmission line a surge
impedance of 400
arrives at a point where the line continues into a cable 1km long having
a total inductance of
H256
and total capacitance of
F165.0
. At the end of the cable a
transformer is connected having surge impedance
1000
. Find the surge voltage
distribution
sec12
after the surge arrives at the live cable junction.
6
OR
*0458*
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