# Switch Gear and Protection 1

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Switch Gear and Protection 1

Part 1: List for questions and answers of Switch Gear and Protection

Q1. Circuit breakers usually operate under

b) Sub transient state of short circuit current

c) Transient state of short circuit current

d) None of these

Q2. What is switchgear?

a) An apparatus used for switching, controlling and protecting the electrical circuits and equipments

b) It detects the faults only

c) It corrects the faults only

d) All of the above

Q3. A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?

a) 35 kA

b) 49 kA

c) 70 kA

d) 89 kA

Q4. A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is its symmetrical breaking current?

a) 1200 A

b) 3600 A

c) 35 kA

d) 104.8 kA

Q5. What is the actuating quantity for the relays?

a) Magnitude

b) Frequency

c) Phase angle

d) All of these

Q6. What are the main disadvantages of using oil as the quenching medium in the circuit breakers?

a) Need periodical replacement

b) Risk of formation of explosive mixture with air

c) Possibility of causing fire hazards

d) All of the above

Q7. What is the relation between the fusing current and the diameter of the wire?

a) I=kd3

b) I=kd3/2

c) I=kd2

d) I=kd2/3

Q8. Which of the following circuit breakers has the lowest operating voltage?

a) SF6 circuit breaker

b) Air break

c) Air blast

d) Minimum oil circuit breaker

Q9.The most efficient torque producing actuating structure for the induction type relays is

b) Watt hour meter structure

c) Induction cup structure

d) Single induction loop structure

Q10. Plug setting of a electromagnetic relay can be altered by varying

a) Number of ampere turns

b) Air gap of magnetic path

d) None of these

Q11. On what factor does the operating speed of the relay depend?

a) Rate of flux built up

b) Armature core air gap

c) Spring tension

d) All of these

Q12. Protective relays can be designed to respond to ___________.

a) Light intensity, impedance

b) Temperature, resistance, reactance

c) Voltage and current

d) All of these

Q13. What is the purpose of back up protection?

a) To increase the speed

b) To increase the reach

c) To leave no blind spot

d) To guard against failure of primary

Q14. What is the major cause of the failure of the circuit breaker?

a) Trip circuit open

b) Trip latch defective

c) Spring defective

d) All of these

Q15. Why are the isolators used?

a) Break abnormal current

b) Making under fault conditions

c) Breaking the circuit under no load condition

d) None of the above

Q16. The isolators used in the transmission lines are capable of breaking

a) Fault current

b) No current

c) Charging current

Q17. For which among the following the current ratings are not required?

a) Circuit breakers

b) Relays

c) Isolators

Q18. Why is an isolator installed?

a) To isolate one portion of the circuit from another

b) As an substitute for the circuit breaker

c) It used on either sides of the circuit breaker

d) Both (a) and (c)

Q19. What is the making to breaking current ratio for an extra high voltage circuit breaker?

a) More than 1

b) Equal to 1

c) Less than 1

d) A negative value

Q20. What is the making capacity of the circuit breaker?

a) Less than the asymmetrical breaking capacity of the breaker

b) Greater than the asymmetrical breaking capacity of the breaker

c) Equal to the asymmetrical breaking capacity of the breaker

d) Equal to the symmetrical breaking capacity of the breaker

Part 1: List for questions and answers of Switch Gear and Protection