Switch Gears

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. When all the three phases are short circuited, it gives rise to ....currents?

#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 rating of fuse is expressed in terms of.....?

#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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