# Switch Gear and Protection 6

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Switch Gear and Protection 6

Part 6: List for questions and answers of Switch Gear and Protection

Q1. Which circuit breaker is preferred to be installed in extra high voltage AC system?

a) Bulk oil type circuit breaker

b) Air blast circuit breaker

c) SF6 circuit breaker

d) Vacuum circuit breaker

Q2. Which among these circuit breakers produce the least arc energy?

a) Plain oil

b) Minimum oil

c) Air blast

d) Air break

Q3. The rating of the circuit breaker is usually determined on the basis of ____________ fault

a) Symmetrical

b) Line to line

c) Single line to ground

d) Double line to ground

Q4. Which of the following circuit breaker is highly reliable and has a least maintenance?

a) Oil circuit breakers

b) Air blast

c) Vacuum circuit breakers

d) SF6 circuit breakers

Q5. Circuit breakers usually operate under

b) Sub transient state of short circuit current

c) Transient state of short circuit current

d) None of these

Q6. 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

Q7. A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?

a) 35kA

b) 49kA

c) 70kA

d) 89kA

Q8. The breaking capacity of a three phase circuit breaker is given by

a) Service line voltage * rated symmetrical current in amperes * 10^-6 MVA

b) Squre root of 3 * Service line voltage * rated symmetrical current in amperes * 10^-6 MVA

c) 1.1* Service line voltage * rated symmetrical current in amperes * 10^-6 MVA

d) Squre root of 2 * Service line voltage * rated symmetrical current in amperes * 10^-6 MVA

Q9.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

Q10. 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)

Q11. For which among the following the current ratings are not required?

a) Circuit breakers

b) Relays

c) Isolators

Q12.The isolators used in the transmission lines are capable of breaking

a) Fault current

b) No current

c) Charging current

Q13.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

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. 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

Q16. What is the actuating quantity for the relays?

a) Magnitude

b) Frequency

c) Phase angle

d) All of these

Q17. Protective relays can be designed to respond to ___________

a) Light intensity, impedance

b) Temperature, resistance, reactance

c) Voltage and current

d) All of these

Q18. 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

Q19. 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

Q20. What is the actuating quantity for the relays?

a) Magnitude

b) Frequency

c) Phase angle

d) All of these

Part 6: List for questions and answers of Switch Gear and Protection