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