Switchgear and Protection MCQs Part 11

Switchgear and Protection MCQs Part 11

Which of the below mentioned fault imposes severest duty on circuit breaker

Which of the below mentioned fault imposes severest duty on circuit breaker:

1. Line to Ground fault
2. Line to Line fault
3. Line to Line to Line fault
4. Three phase fault

Correct answer: 4. Three phase fault

Certain power system has capacitance and inductance values 0.01 µF and 1 H

Certain power system has capacitance and inductance values 0.01 µF and 1 H. The instantaneous value of current to be interrupted is 10 A. What is the value of voltage appearing across contacts of circuit breaker:

1. 10 kV
2. 100 kV
3. 10000 kV
4. None of these

Correct answer: 2. 100 kV

Explanation:

Voltage across CB, v = i√(L/C)

v = 10 √(1 / 0.01 * 10^-6) = 100000 V = 100 kV

The fuse normally protects the system against

The fuse normally protects the system against:

1. Lightening surges
2. Over-current
3. Under-current
4. Resonance

Correct answer: 2. Over-current

The making current of a circuit breaker is generally specified in terms of

The making current of a circuit breaker is generally specified in terms of:

1. Peak value
2. Average value
3. RMS value
4. None of these

Correct answer: 1. Peak value

Capacitive circuit breaking results in

Capacitive circuit breaking results in:

1. Open circuit
2. Short circuit
3. Voltage surge
4. None of these

Correct answer: 3. Voltage surge