Switchgear protections Archives - MCQ and Quiz for Exams

1. In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

Have low contact resistance

Be clean and smooth

Be of sufficient size and proper shape

Have all above properties

Detailed SolutionIn order that current should flow without causing excessive heating or voltage drop, the relay contacts should

2. Arc in a circuit breaker is interrupted at

zero current

maximum current

minimum voltage

maximum voltage

Detailed SolutionArc in a circuit breaker is interrupted at

3. The relay with inverse time characteristic will operate within

1.5 sec

5 to 10 sec

5 to 20 sec

20 to 30 sec E. none of the above

Detailed SolutionThe relay with inverse time characteristic will operate within

4. Which of the following circuit breakers has high reliability and minimum maintenance ?

Air blast circuit breakers

Circuit breaker with SF6 gas

Vacuum circuit breakers

Oil circuit breakers

Detailed SolutionWhich of the following circuit breakers has high reliability and minimum maintenance ?

5. The interaction between a transmission line and communication line is minimized by

transposing transmission as well as communication lines

increasing the height of the trans-mission line tower

increasing the distance between the two lines

all of the above

Detailed SolutionThe interaction between a transmission line and communication line is minimized by

6. Oil switches are employed for

low currents circuits

low voltages circuits

high voltages and large currents circuits

all circuits

Detailed SolutionOil switches are employed for

7. Which of the following devices will receive voltage surge first travelling on the transmission line ?

Lightning arresters

Relays

Step-down transformer

Switchgear

Detailed SolutionWhich of the following devices will receive voltage surge first travelling on the transmission line ?

8. For cost and safety, the outdoor substations are installed for voltages above

11 kV

33 kV

60 kV

110 kV

Detailed SolutionFor cost and safety, the outdoor substations are installed for voltages above

9. An efficient and a well designed protective relaying should have

good selectivity and reliability

economy and simplicity

high speed and selectivity

all of the above

Detailed SolutionAn efficient and a well designed protective relaying should have

10. On which of the following effects of electric current a fuse operates?

Photoelectric effect

Electrostatic effect

Heating effect

Magnetic effect

Detailed SolutionOn which of the following effects of electric current a fuse operates?

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