Switch Gears

#1. An air break switch is designed to open a circuit under.....?

no load

under load

half load

#2. An isolator is designed to open a circuit under.....?

no load

half load

full load

#3. The outdoor type switchgear is used for voltages beyond.....kV?

11

33

66

132

#4. Isolator is an ..... switch?

oil

mica

air

wood

#5. Short circuit current are due to....?

single phase to earth fault

phase to phase fault

all phases to earth fault

all the above

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

symmetrical current

unsymmetrical current

fault current

#7. The most common type fault in over head lines is.....?

single phase to ground

phase to phase

two phase to ground

three phase to ground

#8. Reactors are used in power system is to .....?

avoid short circuit current

limit short circuit current

increase short circuit current

all the above

#9. Reactors are connected ..... with the powe system?

in series

in parallel

in series parallel

#10. A 500 kVA transformer has a reactance of 5%. its reactance at 1000kVA base is.....?

75%

50%

25%

10%

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....?

open the circuit

protect the line

protect the appliances

prevent excessive currents from flow through the circuit

#12. Buchholz relay is used on....?

instrument transformers

air cooled transformers

oil immersed power transformers

distribution transformers

#13. Mho relay is used to protect.....?

long transmission line

short transmission line

medium transmission line

all the above

#14. The leakage resistance of a 50km long cable is 1Mohm. for a 100 km long cable is.....?

2 Mohm

0.5 Mohm

0.6 M ohm

3 Mohm

incorrect

(50×1)/100=0.5

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

volts

KVA

VAR

amperes

#16. Reactance relay are employed for phase fault in....?

short line

medium line

long line

any of the above

#17. An air blast circuit breaker is usually employed for.....?

short duty

medium duty

long duty

repeated duty

#18. Buchholz relay cannot be used on.....?

oil immersed power transformer

600 kV transformer

three phase transformer

air cooled transformer

#19. Lightining arrestor is connected....?

to circuit breaker

in series with the line

between line and earth

to a pole near the line

#20. Differential relays are connected to protect the equipment against.....?

over current

over voltage

internal faults

reverse current

#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....?

25000

50000

34000

2000

#22. In a balanced 3 phase system, negative and zero phase sequence currents are....?

negative

positive

zero

#23. Merz price protection is employed for protection of....?

transformers

alternators

transmission lines

both alternators and transformers

#24. Which relay is used for detect and protect internal faults of a transformer?

distance relay

mho relay

impedence relay

buchholz relay

#25. The over voltage surges in power systems may be caused by...?

lightning

switching

resonance

all the above

#26. Lightning arresters are used in power system to protect electrical equipments against....?

over current effect

over voltage due to indirect lightning stroke

direct lightning strokes

power frequency over voltages

#27. Series capacitor is used in a transmission line to....?

reduce line losses

improve power factor

limit short circuit current

compensate the voltage drop

#28. Which of the following is the protective device against lightning over voltages?

rod gaps and horn gaps

eartbing screen

surge absorber

all the above

#29. Fusing factor is the ratio of.....?

fusing current x current rating of fuse

minimum fusing current / current rating of fuse

current rating of fuse / minimum fusing current

#30. fusing factor of HRC Fuse is....?

zero

1

1.1

1.4

#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?

2

4

6

4.5

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....?

generator

bus bar

transformer

circuit breaker

#33. During arcing ground conditions, the phase voltage of the system rises to.....?

5 times its normal value

1.73 times its normal value

2.4 times its normal value

10 times its normal value

#34. Isolators are capable of breaking.....?

no load

fault current

full load current

charging current

#35. Compare to the breaking capacity of a circuit breaker, its making capacity should be....?

less

more

equal

none of the above

making capacity= 2.55 x brekimg capacity

#36. Fusing factor of LRC fuse will be.....?

1.1

1

1.2

1.4

#37. The transient voltage that appears across the contacts at or near current zero during arcing period is called.....?

arc voltage

restriking voltage

recovery voltage

#38. Phenomenon of current interruption before the natural current zero is reached is called.....?

capacitive current breaking

resistance switching

current choping

breaking capacity

#39. The peak value of current during the first cycle of current wave after the closure of circuit breaker is known as.....?

current chopping

making capacity

peak value

breaking capacity

#40. In circuit breaker, the length of the arc increases, its resistance is .......?

decreased

increased

doubled

same

#41. Current chopping mainly occurs in ...... circuit breakers?

vaccum circuit breaker

air blast circuit breaker

oil circuit breaker

forced blast circuit breaker

#42. Surge absorber ...... the energy of travelling waves?

reflects

absorbs

diverts

partially absorb and partially diverts

#43. In low oil circuit breakers, which type of material used for insulation purpose?

solid material

liquid

hot oil

gas

porcelain used

#44. Fuse material is made by alloy of .....?

copper and zinc

copper and tin

tin and lead

tin and zinc

#45. A lightning arrester provides.....?

low resistance path

low impedence path

high resistance path

high impedence path

#46. The operating time of a fuse is ..... than that of circuit breaker?

less

greater

doubled

quadrupled

fuse= 0.002 sec..

CB = 0.1 to 0.2 sec

#47. A fuse element have .......?

low conductivity

high cost

low melting point

high melting point

#48. The value of fusing factor is......?

1

zero

less than 1

more than 1

#49. A balanced 3 phase system consists of....?

positive sewuence current only

zero sequence current only

negative sequence current only

all the above

#50. The material used in liquid fuse is.....?

water

oil

SF6

carbon tetra chloride

#51. Main purpose of oil in Oil circuit breaker is to....?

quenching arc

provide insulation

for coolinv

all the above

#52. The air blast circuit breakers for 400kV system are designed to operate in.....?

2 ms

2s

50 ms

50 s

#53. Time current characteristics of a fuse is......?

linear

non linear

curved

inverse

#54. Fuse element is generally made of.....?

copper

silver

aluminium

gold

#55. Breaking capacity of fuse ...... than circuit breaker?

smaller

higher

halved

doubled

#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.....?

#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.....?

#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?

#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....?

#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?

#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?

#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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