# Power System Protection MCQs Part 13

Power System Protection MCQs Part 13

## In case of the absence of a fourth conductor serving as return path, the zero-sequence current will

In case of the absence of a fourth conductor serving as return path, the zero-sequence current will:

1. Not flow
2. Flow
3. Flow but less than 1.732 times
4. Flow but 4 times more the actual value

## The value of first cycle symmetrical fault current at certain bus is 30 kA. What is value of close and latch rating in RMS of circuit breaker

The value of first cycle symmetrical fault current at certain bus is 30 kA. What is value of close and latch rating in RMS of circuit breaker:

1. 42.98 A
2. 48 A
3. 52.54 A
4. 69.24 A

Solution: Close and latch (RMS) = 1.6 * 30 = 48 A

## Larger X/R ratios decay quickly as compared to small X/R ratios

Larger X/R ratios decay quickly as compared to small X/R ratios:

1. True
2. False

## Which of follow has no angular displacement between the phases

Which of follow has no angular displacement between the phases:

1. Negative phase sequence
2. Positive phase sequence
3. Zero phase sequence
4. All of these

Correct answer: 3. Zero phase sequence

## For zero-sequence current to flow the ground connection is

For zero-sequence current to flow the ground connection is:

1. Required
2. Not required