Power System MCQs Part 2

Power System MCQ Part 2.

Skin effect increases

Skin effect increases:

1. Resistance of power line
2. Inductance of power line
3. Capacitance of power line
4. All of these

Correct answer: 1. Resistance of power line

Definition of short transmission lines

The lines below _____ are considered as short transmission lines:

1. 20 km
2. 80 km
3. 240 km
4. 600 km

Correct answer: 2. 80 km

Voltage regulation of transmission line is greatest for which of following power factors

Voltage regulation of transmission line is greatest for which of following power factors:

1. Leading PF
2. Lagging PF
3. Both of these
4. None of these

Correct answer: 2. Lagging PF

Which type of insulator is recommended for places where direction of transmission line changes

Which type of insulator is recommended for places where the direction of transmission line changes:

1. Pin type
2. Suspension type
3. Strain type
4. Shackle type

Correct answer: 3. Strain type

A CT having a secondary current of 5 A, and an RF of 4.0 can produce a secondary current up to

A CT having a secondary current of 5 A, and an RF of 4.0 can produce a secondary current up to:

1. 0.8 A
2. 1.25 A
3. 4 A
4. 20 A

Correct answer: 4. 20 A

The rating factor is in a short form known as RF of a current transformer and it implies the maximum continuous current that can flow through the CT primary without exceeding the thermal capability of the CT windings.

String efficiency of high voltage transmission lines is around

String efficiency of high voltage transmission lines is around:

1. 20%
2. 40%
3. 80%
4. 99%

Correct answer: 3. 80%

A generator has an impedance value of 3 Ω. What is its base impedance value in per-unit, considering bases of 1000 MVA and 22 kV

A generator has an impedance value of 3 Ω. What is its base impedance value in per-unit, considering bases of 1000 MVA and 22 kV:

1. 0.225 Ω
2. 0.484 Ω
3. 0.876 Ω
4. 1.22 Ω
5. None of above

Correct answer: 2. 0.484 Ω

Solution:

Base Impedance = (Base kV(L-L))^2 / Base MVA 3ɸ = 22^2 / 1000 = 0.484 Ω

Which of following will result in an increase of cost of an overhead transmission line

Which of the following will result in an increase in cost of an overhead transmission line:

1. Increasing conductor spacing
2. Decreasing conductor spacing
3. Decreasing ground clearance
4. None of these

Correct answer: 1. Increasing conductor spacing

Magnetizing of the current transformer can affect its accuracy

Magnetizing of the current transformer can affect its accuracy:

1. True
2. False

Correct answer: 1. True

Usually, the magnetization of the CT affects accuracy, so demagnetization is recommended before testing a CT.

Potential across the various discs of suspension string is different. This is primarily due to

Potential across the various discs of suspension string is different. This is primarily due to:

1. Self-capacitance
2. Shunt capacitance
3. Both of these
4. None of these

Correct answer: 2. Shunt capacitance