# Power System Protection MCQs Part 21

Power System Protection MCQs Part 21

## The normal current in power line is 120 A. If short circuit fault occurs on the line, the one can expect the short-circuit current to be

The normal current in power line is 120 A. If short circuit fault occurs on the line, the one can expect the short-circuit current to be:

1. 120 A
2. 200 A
3. 500 A
4. More than 1000 A

Correct answer: 4. More than 1000 A

Explanation: The short circuit current is generally more than 10 times of the normal current. Therefore, one can expect the short-circuit current to be more than 1000 A.

## The fusing current I for a round wire having diameter d is given mathematically by

The fusing current I for a round wire having diameter d is given mathematically by:

1. I ∝ d
2. I ∝ d^2
3. I ∝ d^3/2
4. None of these

Correct answer: 3. I ∝ d^3/2

## Which of the following CB is generally used in railway applications

Which of the following CB is generally used in railway applications:

1. Air break CB
2. Bulk oil CB
3. Low oil CB
4. SF6 CB

Correct answer: 1. Air break CB

## A fuse is always connected in

A fuse is always connected in:

1. Series with circuit
2. Parallel with circuit
3. Series-parallel configuration with circuit
4. None of these

Correct answer: 1. Series with circuit

## Arc interruption takes place in oil circuit breaker when

Arc interruption takes place in oil circuit breaker when:

1. Voltage goes through zero
2. Current goes through zero
3. Contacts move apparat
4. None of these

Correct answer: 2. Current goes through zero

See complete list of Power System Protection MCQs here

Electrical Engineering MCQs