# 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:

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

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

## 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