# Switchgear and Protection MCQs Part 12

Switchgear and Protection MCQs Part 12

## For interrupting high voltage and low current, which of following circuit breaker is preferred

For interrupting high voltage and low current, which of following circuit breaker is preferred:

1. Air blast CB
2. Vacuum CB
3. Oil CB
4. All of these

Correct answer: 2. Vacuum CB

## Which of the below mentioned relays is more sensitive

Which of the below mentioned relays is more sensitive:

1. 1 VA
2. 2 VA

Options:

1. a) 1 VA
2. b) 2 VA
3. Both are equal in terms of sensitivity
4. Data insufficient

Correct answer: 1. a) 1VA

## In order to reduce the voltage surges due to current chopping and capacitive current breaking, it is a practice to

In order to reduce the voltage surges due to current chopping and capacitive current breaking, it is a practice to:

1. A resistor across contacts of CB
2. A capacitor across contacts of CB
3. An inductor across contacts of CB
4. None of these

Correct answer: 1. A resistor across contacts of CB

## Resistance switching is normally resorted in case of

Resistance switching is normally resorted in case of:

1. Air blast CB
2. Bulk oil CB
3. Low oil CB
4. All of above

Correct answer: 1. Air blast CB

## An over-current relay having current setting of 150% is connected to supply circuit through a CT having ration 400/5. The pick-up current is

An over-current relay having current setting of 150% is connected to supply circuit through a CT having ration 400/5. The pick-up current is:

1. 2.5 A
2. 5 A
3. 7.5 A
4. 10 A

Correct answer: 3. 7.5 A

Solution:

Rated secondary current = 5 A

——————–

Pick-up current = Rated secondary current * Current setting

= 5 * 1.5 = 7.5 A