Here are High Voltage Engineering MCQs (Chapterwise).
1. What is the purpose of using corona rings in high voltage transmission lines?
a) To measure voltage
b) To protect against lightning
c) To reduce corona discharge
d) To increase corona discharge
View Answer
Explanation: Corona rings are used to reduce corona discharge and associated power losses in high voltage transmission lines.
2. Which insulating material is commonly used in high voltage cables?
a) XLPE (Cross-linked polyethylene)
b) PVC (Polyvinyl chloride)
c) Wood
d) Rubber
View Answer
Explanation: XLPE is a commonly used insulating material in high voltage cables due to its excellent electrical properties.
3. Which among the following diodes is preferred for high-voltage rectifiers?
a) Selenium diode
b) Gunn diode
c) Laser diode
d) Silicon diode
View Answer
Explanation: Silicon diode is a crystal diode that uses silicon as a semiconductor. Silicon diodes with peak inverse voltage(PIV) of 1kV to 2kV are used in high-voltage rectifiers. PIV refers to the maximum voltage a diode can withstand in the reverse-biased direction before breakdown.
4. Which is the simplest voltage doubler circuit?
a) Cockroft-Walton
b) Greinacher
c) Cascaded and Cockroft-Walton
d) Cascaded
View Answer
Explanation: Greinacher is the simplest voltage doubler circuit. It comprises of two resistors and two capacitors. Cockroft–Walton and cascade circuit are voltage multiplier circuits.
5. How the sag at higher stages can be reduced in a voltage multiplier circuit?
a) by decreasing the capacitance in the higher stages
b) by decreasing the capacitance in the lower stages
c) by increasing the capacitance in the higher stages
d) by increasing the capacitance in the lower stages
View Answer
Explanation: The sag at higher stages can be reduced in a voltage multiplier circuit by increasing the capacitance in the lower stages. The voltages of the higher stages begin to sag because of the electrical impedance of the capacitors in the lower stages.
6. What is meant by voltage regulation?
a) Change of maximum voltage across the load from the no load theoretical value expressed as a percentage of no load voltage
b) Change of average voltage across the load from the no load theoretical value expressed as a percentage of average voltage
c) Change of average voltage across the load from the no load theoretical value expressed as a percentage of no load voltage
d) Change of mean voltage across the load from the no load theoretical value expressed as a percentage of no load voltage
View Answer
Explanation: The change occurred in voltage is referred to as the voltage drop. The ratio of voltage drop to the no load voltage is known as voltage regulation. It is defined as the change of average voltage across the load from the no load theoretical value expressed as a percentage of no load voltage.
7. What is the speed of the electric motor which drives the belt?
a) 10000-20000m/min
b) 1000-2000m/min
c) 10-20m/min
d) 100-200m/min
View Answer
Explanation: The belt is drive by an electric motor. The speed of the electric motor ranges between 1000-2000m/min. The belt moves through an insulated metal electrode. The charge is sprayed to this moving belt.
8. What is the power output when capacitor is charged with dc voltage?
a) \(P=C^2 \frac{dC}{dt}\)
b) \(P=C^2 \frac{dV}{dt}\)
c) \(P=V^2 \frac{dC}{dt}\)
d) P=0
View Answer
Explanation: The power input the circuit is given by the formula \(P=CV \frac{dV}{dt}+V^2 \frac{dC}{dt}\). Whenever the capacitor is charged with a dc voltage V, the power output is given by \(P=V^2 \frac{dC}{dt}\) since C \(\frac{dV}{dt}\) becomes zero.
9. What is the third winding in the transformer called?
a) primary winding
b) secondary winding
c) high voltage winding
d) meter winding
View Answer
Explanation: Low and high voltage windings are the normal winding found in a transformer. The meter winding, also known as the third winding is the additional winding used to measure the output voltage.
10. How is the high short circuit current limited in the cascade transformers?
a) by using limiting reactors in input stage
b) by using limiting reactors in output stage
c) by using limiting reactors in between the transformer units
d) by using limiting reactors in input and output stage
View Answer
Explanation: There are chances of the occurrence of excessive load currents. Thus to limit the high short circuit current, limiting reactors are employed at the input stage. The short circuit currents are capacitive in nature.
11. What is the effective capacitance in wave shaping circuit?
a) \(C=\frac{C_1 C_2}{2C_1 + 2C_2}\)
b) \(C=3 \frac{C_1 C_2}{C_1 + C_2}\)
c) \(C=\frac{C_1 C_2}{C_1 + C_2}\)
d) \(C=2 \frac{C_1 C_2}{C_1 + C_2}\)
View Answer
Explanation: The effective capacitance in wave shaping circuit is \(C=\frac{C_1 C_2}{C_1 + C_2}\), C1 is the generator capacitance and C2 is the load capacitance. The circuit inductance is very small and hence is not taken into account.
12. What is the range of load capacitors in an impulse generator circuit?
a) 1-10nF
b) 50-70nF
c) 10-100nF
d) 20-30nF
View Answer
Explanation: The range of load capacitors in an impulse generator circuit is 1-10nF. They can be of the compressed gas type or oil filled type.
13. What is the tail time of switching impulse voltage according to Indian Standards?
a) 250 μs
b) 50 μs
c) 50 μs
d) 2500 μs
View Answer
Explanation: A switching surge is a voltage produced in the system due to the sudden opening and closing of switches. It is of short duration and is transient in nature. The waveform of switching surge is not unique. The front time of switching impulse voltage according to Indian Standards is 25 00μs.
14. What is the range of capacitors in an impulse current generator circuit?
a) 0.5-5μF
b) 20-30nF
c) 1-10nF
d) 10-100nF
View Answer
Explanation: The range of load capacitors in an impulse generator circuit is 1-10nF. They are capable of giving high short circuit currents.
15. Which of the following test is used in the factory site for isolating the defective insulation?
a) partial discharge test
b) scanning test
c) corrosion test
d) high-voltage tests
View Answer
Explanation: The scanning method is used in the factory site for isolating the defective insulation. Four electrodes are used in scanning method. They are mounted in the form of rings at both ends of the tube so that they have electrical contact with the water. The middle electrodes are energized with high voltage and the other two electrodes are grounded.
Chapterwise Multiple Choice Questions on High Voltage Engineering
- Generation of High DC and AC Voltages
- Generation of High Frequency AC Voltages
- Generation of Impulse Voltages
- Generation of impulse Current
- Measurement of High Voltage and Current
- High Voltage Testing of Electrical Equipment
1. MCQ on Generation of High DC and AC Voltages
The section contains multiple choice questions and answers on the generation of high DC and AC voltages, voltage multiplier circuit, voltage regulation, ripple and ripple factor, DC voltage regulation, Van de Graaff generator, and electrostatic generator.
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2. Generation of High Frequency AC Voltages
The section covers questions and answers on cascade transformer and resonant transformer.
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3. Generation of Impulse Voltages
The section contains MCQs on the generation of impulse voltages, circuits for producing impulse, waveshape control, Marx circuit, components of multistage impulse generator, and the generation of switching surges.
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4. Questions on Generation of Impulse Current
The section contains multiple choice questions and answers on the generation of impulse and rectangular current.
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5. Measurement of High Voltage and Current
The section covers questions and answers on sphere gaps, electrostatic voltmeter, voltage dividers, impulse voltage measurement, and measurement of high impulse currents.
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6. High Voltage Testing of Electrical Equipment
The section contains MCQs on high voltage testing of electrical equipment and testing of bushings.
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Wish you the best in your endeavor to learn and master High Voltage Engineering!
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