Switch Gear and Protection

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Code No: A107320205 Set No. 1 JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

III B.Tech. II Sem., I Mid-Term Examinations, March – 2010 SWITCH GEAR AND PROTECTION

Objective Exam Name: ______________________________ Hall Ticket No. A

Answer All Questions. All Questions Carry Equal Marks.Time: 20 Min. Marks: 20. I Choose the correct alternative:

1. Circuit breakers are essentially [ ] a) circuits to break the system b) current carrying contacts called electrodes c) arc extinguishers d) transformers to isolate the two systems

2. Basic problem of a circuit breaker is to [ ] a) extinguish the arc b) transmit large power

c) maintain the arc d) emit the ionizing electronics 3. Air blast circuit breaker (ABCB) is operated at a pressure of [ ] a) 1 to 5 kg/cm2 b) 5 to 10 kg/cm2 c) 20-30 kg/cm2 d) 10-20 kg/cm2

4. The voltage appearing across the contacts after opening of the circuit breaker is called [ ] a) operating voltage b) surge voltage c) arc voltage d) recovery voltage 5. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring

[ ] a) constantly the electrical quantities which differ during normal and abnormal conditions b) currents during abnormal conditions c) voltage during abnormal conditions d) relay currents or voltages for protective purposes 6. Burden of a protective relay is the power [ ] a) developed by the relay current b) absorbed by the circuit of the relay c) factor of the relay circuit including tripping will d) flowing in the circuit breaker 7. A differential relay measures the vector difference between [ ] a) two powers b) two voltage c) two currents d) two or more similar electrical quantities 8. To avoid the effect of wave chopping by arcing horns, the insulation level at the approach span is

maintained [ ] a) the same as that for the normal line b) more than that for the normal line c) less than that for the normal line d) none 9. ______________ cannot be used as arc quenching medium [ ] a) water b) sulphur hexafluoride c) oil d) sodium chloride 10. Directional relays are based on flow of [ ] a) voltage wave b) current c) power d) leakage currents

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Code No: A107320205 -2- Set No. 1 II. Fill in the blanks: 11. Under normal operating conditions, the contacts of the circuit breaker remain __________ 12. Under fault conditions, ________ supplies information to the circuit breaker to open. 13. When the contacts of a circuit breaker opened, on the occurrence of a fault, an ________ struck. 14. In an oil circuit breaker _______ is used as the arc quenching medium. 15. Current chopping mainly occurs ______ circuit breakers. 16. Induction relays ____ be used with d.c. quantities. 17. Back up protection functions when _________ 18. The most important stator winding fault on alternator is _______ fault. 19. The most commonly used system for the protection of generator is _______ 20. The relay is which the operation is governed by the ratio of applied voltage to current in the

potential circuit is called _______

-oOo-

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[ ] a) constantly the electrical quantities which differ during normal and abnormal conditions b) currents during abnormal conditions c) voltage during abnormal conditions d) relay currents or voltages for protective purposes 3. Burden of a protective relay is the power [ ] a) developed by the relay current b) absorbed by the circuit of the relay c) factor of the relay circuit including tripping will d) flowing in the circuit breaker 4. A differential relay measures the vector difference between [ ] a) two powers b) two voltage c) two currents d) two or more similar electrical quantities 5. To avoid the effect of wave chopping by arcing horns, the insulation level at the approach span is

maintained [ ] a) the same as that for the normal line b) more than that for the normal line c) less than that for the normal line d) none 6. ______________ cannot be used as arc quenching medium [ ] a) water b) sulphur hexafluoride c) oil d) sodium chloride 7. Directional relays are based on flow of [ ] a) voltage wave b) current c) power d) leakage currents 8. Circuit breakers are essentially [ ] a) circuits to break the system b) current carrying contacts called electrodes c) arc extinguishers d) transformers to isolate the two systems



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Code No: A107320205 -2- Set No. 2 II. Fill in the blanks:

11. In an oil circuit breaker _______ is used as the arc quenching medium. 12. Current chopping mainly occurs ______ circuit breakers. 13. Induction relays ____ be used with d.c. quantities. 14. Back up protection functions when _________ 15. The most important stator winding fault on alternator is _______ fault. 16. The most commonly used system for the protection of generator is _______ 17. The relay is which the operation is governed by the ratio of applied voltage to current in the

potential circuit is called _______

18. Under normal operating conditions, the contacts of the circuit breaker remain __________ 19. Under fault conditions, ________ supplies information to the circuit breaker to open. 20. When the contacts of a circuit breaker opened, on the occurrence of a fault, an ________ struck.

-oOo-

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1. Burden of a protective relay is the power [ ] a) developed by the relay current b) absorbed by the circuit of the relay c) factor of the relay circuit including tripping will d) flowing in the circuit breaker 2 A differential relay measures the vector difference between [ ] a) two powers b) two voltage c) two currents d) two or more similar electrical quantities 3. To avoid the effect of wave chopping by arcing horns, the insulation level at the approach span is

maintained [ ] a) the same as that for the normal line b) more than that for the normal line c) less than that for the normal line d) none 4. ______________ cannot be used as arc quenching medium [ ] a) water b) sulphur hexafluoride c) oil d) sodium chloride 5. Directional relays are based on flow of [ ] a) voltage wave b) current c) power d) leakage currents 6. Circuit breakers are essentially [ ] a) circuits to break the system b) current carrying contacts called electrodes c) arc extinguishers d) transformers to isolate the two systems




[ ] a) constantly the electrical quantities which differ during normal and abnormal conditions b) currents during abnormal conditions c) voltage during abnormal conditions d) relay currents or voltages for protective purposes

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Code No: A107320205 -2- Set No. 3 II. Fill in the blanks: 11. Induction relays ____ be used with d.c. quantities. 12. Back up protection functions when _________ 13. The most important stator winding fault on alternator is _______ fault. 14. The most commonly used system for the protection of generator is _______ 15. The relay is which the operation is governed by the ratio of applied voltage to current in the

potential circuit is called _______ 16. Under normal operating conditions, the contacts of the circuit breaker remain __________ 17. Under fault conditions, ________ supplies information to the circuit breaker to open. 18. When the contacts of a circuit breaker opened, on the occurrence of a fault, an ________ struck. 19. In an oil circuit breaker _______ is used as the arc quenching medium. 20. Current chopping mainly occurs ______ circuit breakers.

-oOo-

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1. To avoid the effect of wave chopping by arcing horns, the insulation level at the approach span is maintained [ ]

a) the same as that for the normal line b) more than that for the normal line c) less than that for the normal line d) none 2. ______________ cannot be used as arc quenching medium [ ] a) water b) sulphur hexafluoride c) oil d) sodium chloride 3. Directional relays are based on flow of [ ] a) voltage wave b) current c) power d) leakage currents 4. Circuit breakers are essentially [ ] a) circuits to break the system b) current carrying contacts called electrodes c) arc extinguishers d) transformers to isolate the two systems




[ ] a) constantly the electrical quantities which differ during normal and abnormal conditions b) currents during abnormal conditions c) voltage during abnormal conditions d) relay currents or voltages for protective purposes 9. Burden of a protective relay is the power [ ] a) developed by the relay current b) absorbed by the circuit of the relay c) factor of the relay circuit including tripping will d) flowing in the circuit breaker 10. A differential relay measures the vector difference between [ ] a) two powers b) two voltage c) two currents d) two or more similar electrical quantities

Cont…2

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Code No: A107320205 -2- Set No. 4 II. Fill in the blanks: 11. The most important stator winding fault on alternator is _______ fault. 12. The most commonly used system for the protection of generator is _______ 13. The relay is which the operation is governed by the ratio of applied voltage to current in the

potential circuit is called _______ 14. Under normal operating conditions, the contacts of the circuit breaker remain __________ 15. Under fault conditions, ________ supplies information to the circuit breaker to open. 16. When the contacts of a circuit breaker opened, on the occurrence of a fault, an ________ struck. 17. In an oil circuit breaker _______ is used as the arc quenching medium. 18. Current chopping mainly occurs ______ circuit breakers. 19. Induction relays ____ be used with d.c. quantities. 20. Back up protection functions when _________

-oOo-

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Switch Gear and Protection