Multiple Choice Questions Related with Switch Gears.
#1. An air break switch is designed to open a circuit under…..?
#2. An isolator is designed to open a circuit under…..?
#3. The outdoor type switchgear is used for voltages beyond…..kV?
#4. Isolator is an ….. switch?
#5. Short circuit current are due to….?
#6. Short circuit current are due to….?
#7. The most common type fault in over head lines is…..?
#8. Reactors are used in power system is to …..?
#9. Reactors are connected ….. with the powe system?
#10. A 500 kVA transformer has a reactance of 5%. its reactance at 1000kVA base is…..?
incorrect
% reactance at base kVA=( base kVA/rated kVA)×%reactance at rated kVA
=1000/500 × 5
=10%
#11. The primary function of a fuse is to….?
#12. Buchholz relay is used on….?
#13. Mho relay is used to protect…..?
#14. The leakage resistance of a 50km long cable is 1Mohm. for a 100 km long cable is…..?
incorrect
(50×1)/100=0.5
#15. The leakage resistance of a 50km long cable is 1Mohm. for a 100 km long cable is…..?
#16. Reactance relay are employed for phase fault in….?
#17. An air blast circuit breaker is usually employed for…..?
#18. Buchholz relay cannot be used on…..?
#19. Lightining arrestor is connected….?
#20. Differential relays are connected to protect the equipment against…..?
#21. If the percentage reactance of the system upto the fault point is 20% and the base kVA is 10000 then short circuit kVA is….?
#22. In a balanced 3 phase system, negative and zero phase sequence currents are….?
#23. Merz price protection is employed for protection of….?
#24. Which relay is used for detect and protect internal faults of a transformer?
#25. The over voltage surges in power systems may be caused by…?
#26. Lightning arresters are used in power system to protect electrical equipments against….?
#27. Series capacitor is used in a transmission line to….?
#28. Which of the following is the protective device against lightning over voltages?
#29. Fusing factor is the ratio of…..?
#30. fusing factor of HRC Fuse is….?
#31. A relay is connected to a 400/5 current transformer and set at 150%. with a primary fault current of 2400A, Calculated the Plug setting multiplier?
incorrect
pick up value= rated sec.current x current setting= 5 x 1.5=7.5A
fault current in relay coil= 2400 x (5/400)=30A
PSM=30/7.5=4
#32. Location of lightning arrestor should be near….?
#33. During arcing ground conditions, the phase voltage of the system rises to…..?
#34. Isolators are capable of breaking…..?
#35. Compare to the breaking capacity of a circuit breaker, its making capacity should be….?
making capacity= 2.55 x brekimg capacity
#36. Fusing factor of LRC fuse will be…..?
#37. The transient voltage that appears across the contacts at or near current zero during arcing period is called…..?
#38. Phenomenon of current interruption before the natural current zero is reached is called…..?
#39. The peak value of current during the first cycle of current wave after the closure of circuit breaker is known as…..?
#40. In circuit breaker, the length of the arc increases, its resistance is …….?
#41. Current chopping mainly occurs in …… circuit breakers?
#42. Surge absorber …… the energy of travelling waves?
#43. In low oil circuit breakers, which type of material used for insulation purpose?
porcelain used
#44. Fuse material is made by alloy of …..?
#45. A lightning arrester provides…..?
#46. The operating time of a fuse is ….. than that of circuit breaker?
fuse= 0.002 sec..
CB = 0.1 to 0.2 sec
#47. A fuse element have …….?
#48. The value of fusing factor is……?
#49. A balanced 3 phase system consists of….?
#50. The material used in liquid fuse is…..?
#51. Main purpose of oil in Oil circuit breaker is to….?
#52. The air blast circuit breakers for 400kV system are designed to operate in…..?
#53. Time current characteristics of a fuse is……?
#54. Fuse element is generally made of…..?
#55. Breaking capacity of fuse …… than circuit breaker?
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