Switchgear and Protection MCQs Part 11
Switchgear and Protection MCQs Part 11
Contents
Which of the below mentioned fault imposes severest duty on circuit breaker
Which of the below mentioned fault imposes severest duty on circuit breaker:
- Line to Ground fault
- Line to Line fault
- Line to Line to Line fault
- 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:
- 10 kV
- 100 kV
- 10000 kV
- 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:
- Lightening surges
- Over-current
- Under-current
- 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:
- Peak value
- Average value
- RMS value
- None of these
Correct answer: 1. Peak value
Capacitive circuit breaking results in
Capacitive circuit breaking results in:
- Open circuit
- Short circuit
- Voltage surge
- None of these
Correct answer: 3. Voltage surge