1) The stay type of insulators is insulated at a height of not less than _________ m.
a. 5
b. 6
c. 3
d. 4
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2) Post type insulators are generally used in lines operating
a. Above 100 kV
b. Below 33 kV
c. At any voltage level
d. None of these
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3) Which type of insulators is used in guy wires?
a. Stay insulators
b. Shackle insulators
c. Pin type
d. Strain type
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4) Assertion (A): Glazing on ceramic insulators is done to make it smooth and non – absorbent.
Reason (R): Moisture from atmosphere collects on the surface causing electrical breakdown.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true
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Answer
Explanation
Related Ques
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ANSWER: Both A and R are true and R is the correct explanation of A
Explanation:
No explanation is available for this question!
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5) The types of suspension insulators are
a. Hewlett type
b. Inter linking type
c. Cemented cap type
d. All of these
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6) Each disc in a suspension type of insulators is designed for what voltage?
a. 33 kV
b. 22 kV
c. 11 kV
d. 66 kV
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7) Where is the suspension type of insulators mainly used?
a. RCC poles
b. Wooden poles
c. Steel poles
d. Steel towers
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8) The voltage across the various discs of a string of suspension insulators having identical discs is different due to
a. Surface leakage currents
b. Series capacitance
c. Shunt capacitance to ground
d. Series and shunt capacitance
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9) On what factor does the string efficiency of a string of suspension insulators is dependent?
a. Size of the insulator
b. Number of discs in the string
c. Size of tower
d. None of these
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10) The maximum voltage of the disc type insulators is at
a. Same at all points
b. Near the tower or starting of the insulator
c. Near to the conductors
d. None of these
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11) The string efficiency of a high voltage line is around ______.
a. 100 %
b. 80 %
c. 40 %
d. 10 %
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12) What is the voltage across the second unit from the top in case of a suspension type insulator?
a. V2 = V1 (3 + 4K)
b. V2 = V1 (1 + K)
c. V2 = V1 (1 + K2)
d. None of these
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13) Voltage across the string is ___________ times the line voltage.
a. √3
b. √2
c. 1 / √3
d. 1 / √2
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14) In a test by Murray loop for ground fault on 500 m of cable having a resistance of 1.6 Ω / km, the faulty cable is looped with the sound cable of some length and area of cross section. If the ratio of the other two arms of the testing network at balance is 3:1, what is the distance of fault from the testing end of cables?
a. 100 m
b. 200 m
c. 250 m
d. 300 m
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15) A 3 phase over head transmission line is supported by three discs of suspension insulators. The potentials across the first and second insulator are 8 and 11 kV respectively. What is the line voltage and string efficiency?
a. 0.654 and 63.5%
b. 0.375 and 68.3 %
c. 0.527 and 56.34 %
d. 0.287 and 65.258 %
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16) What is the purpose of guard ring?
a. Reduce the earth capacitance of the lowest unit.
b. Increase the earth capacitance of the lowest unit.
c. Reduce the transmission line losses.
d. None of these.
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Answer
Explanation
Related Ques
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ANSWER: Reduce the earth capacitance of the lowest unit.
Explanation:
No explanation is available for this question!
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17) Assertion (A): The string efficiency can be improved by using long cross arms.
Reason (R): Use of long cross arms reduces the ratio of capacity to earth to capacity per insulator thereby increasing the string efficiency.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true
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Answer
Explanation
Related Ques
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ANSWER: Both A and R are true and R is the correct explanation of A
Explanation:
No explanation is available for this question!
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18) Assertion (A): Capacitance grading improves the string efficiency not more than 220 kV.
Reason (R): In capacitance grading the units used are of different capacitance and so are not interchangeable.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true
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19) Which shielding is called the static shielding of the string?
a. Using the guard rings
b. Grading the insulators
c. Increasing the length of cross arms
d. None of these
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20) The insulators fail due to
a. Flash over
b. Short circuits
c. Deposition of dust
d. All of these
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21) The number of discs required for 220 kV ac over head transmission line in clear atmosphere is
a. 10 – 12
b. 21 – 22
c. 12 – 14
d. 5 – 6
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22) At what angle is the water sprayed on the insulator in 50 cycle wet test?
a. 35 °C
b. 40 °C
c. 45 °C
d. 50 °C
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23) What is the value of the wave front and the wave tail of the standard lightning impulse wave used in the impulse voltage withstand test?
a. 50 μ sec and 1.2 μ sec
b. 1.2 μ sec and 50 μ sec
c. 50 μ sec and 2.1 μ sec
d. 2.1 μ sec and 50 μ sec
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24) What is corona?
a. Partial breakdown of air
b. Complete breakdown of air
c. Sparking between the lines
d. None of these
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25) In case of dc voltage, which colour beads are formed near the negative conductor?
a. Reddish
b. Bluish
c. Greenish
d. Violet
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26) In case of dc voltage, smoother _____________ uniform glows near the positive conductor.
a. Yellow
b. Bluish white
c. Reddish white
d. Greenish yellow
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27) Which of the following statements are true related to corona?
1. It causes radio interference.
2. It attenuates lightning surges.
3. It causes power loss.
4. It amplifies switching surges.
The codes are:
a. 1,2,4
b. 1,4
c. 1,2,3
d. 2,3
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28) Which gas is formed near to the conductors by producing a hissing noise?
a. Oxygen
b. Ozone
c. Hydrogen
d. Nitrogen
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29) Corona is observed on
a. AC transmissions only
b. DC transmissions only
c. AC and DC transmissions
d. None of these
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30) Air density factor which depends on the pressure and temperature is given by which of these formulas?
a. δ = (5.92 * b) / (273 + t)
b. δ = (7.92 * b) / (273 + t)
c. δ = (3.92 * b) / (273 + t)
d. δ = (4.92 * b) / (273 + t)
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31) What happens if the voltage applied is equal to the critical disruptive voltage?
a. Corona does not start
b. Corona starts but is not visible
c. Corona starts and is visible
d. Only ionization starts
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32) What is the value of energy distance in case of two parallel conductors?
a. (r + 0.301 * √ r)
b. (r + 0.308 * √ r)
c. (r + 0.501 * √ r)
d. (r + 0.508 * √ r)
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33) As the moisture content in the air increases, what is the effect of this on the disruptive critical voltage?
a. Increases
b. Decreases
c. Remains constant
d. May increases or decrease
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34) What is the value of energy distance in case of co-axial conductors?
a. (r + 0.301 * √ r)
b. (r + 0.308 * √ r)
c. (r + 0.501 * √ r)
d. (r + 0.508 * √ r)
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35) What is the critical disruptive voltage of a three phase line which has a conductor of 2 cm in diameter which are spaced equilaterally 1m apart, if the dielectric strength of air is about 30 kV/cm, and air density about 0.952 and irregularity factor 0.9?
a. 152.36 kV
b. 146.235 kV
c. 144.95 kV
d. 111.235 kV
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36) By what factor does the critical disruptive voltage (Vd) get reduced?
a. 0.6
b. 0.7
c. 0.8
d. 0.9
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37) Higher the frequency, _____________.
a. Lower the corona loss
b. Higher is the corona loss
c. Does not effect
d. Depends on the physical conditions
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38) Which harmonics are generated during the corona, which leads to the increase in corona losses?
a. Third harmonics
b. Fifth harmonics
c. Seventh harmonics
d. None of these
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39) What is the use of bundled conductors?
a. Reduces surface electric stress of conductor
b. Increases the line reactance
c. Decreases the line capacitance
d. None of these
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40) On which factor is the corona loss dependent?
a. Material of the conductor
b. Diameter of the conductor
c. Height of the conductor
d. None of these
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