Earthing And Grounding multiple choice questions
Earthing And Grounding
1. The ground wire is coloureda) Green
b) Black
c) Yellow
d) Red
Answer: Green
2. The neutral wire is coloured
a) Black
b) Blue
c) Red
d) Yellow
Answer: Black
3. Grounding transformer is used where neutral ____________available
a) Is
b) Is not
c) Either A or B
d) None of the above
Answer: Is not
4. In case of earth fault, the underground neutral system___________lead to arcing ground
a) Does
b) Does not
c) Any of the above
d) None of the alarm
Answer: Does
5. In equipment grounding, the enclosure is connected to ___________wire
a) Ground
b) Neutral
c) Phase
d) Either A or B
Answer: Ground
6. Solid grounding is addopted for voltages below
a) 100 V
b) 200 V
c) 400 V
d) 660 V
Answer: 660 V
7. In a star connected system without neutral grounding, zero sequence currents are
a) Zero
b) Phaser sum of phase currents
c) Same as r.m.s. value of phase currents
d) Same as peak value of phase currents
Answer: Zero
8. When the 3-phase system is not grounded and if Single Line to Ground fault occurs, the voltage of the other two healthy phases will
a) Increases
b) Decreases
c) Remains unaffected
d) none of the above
Answer: Increases
9. Generally grounding is provided for
a) only for the safety of the equipment
b) only for the safety of the operating personnel
c) both (a) and (b)
d) none of the above
Answer: both (a) and (b)
10. Moisture content in the soil_______the earth soil resistance
a) increase
b) decrease
c) does not affect
d) none of the above
Answer: decrease
11. The size of the earth or ground wire is based on the
a) maximum fault current carrying through the ground wire
b) rated current carrying capacity of the service line
c) depends on the soil resistance
d) both (a) and (c)
Answer: both (a) and (c)
12. Ground resistance should be designed such that
a) grounding resistance should be as low as possible
b) grounding resistance should be as high as possible
c) grounding resistance should be always zero
d) none of the above
Answer: grounding resistance should be as low as possible
13. Average resistance of human body is
a) 500 ohms
b) 1000 ohms
c) 1500 ohms
d) 2000 ohms
Answer: 1000 ohms
14. Factors on which soil resistance depends
a) depth of the electrode
b) moisture
c) Nacl
d) all the above
Answer: all the above
15. For an EHV equipment for maintenance first it should be isolated and connected to ground because
a) to provide low impedance
b) to discharge the charging capacitance to ground
c) protection for operating personnel
d) both (b) and (c)
Answer: both (b) and (c)
16. When earth fault occurs
a) voltage potential at the earth mat increases due to grounding
b) voltage potential at the earth mat decreases due to grounding.
c) voltage potential at the earth mat remains zero irrespective of fault
d) none of the above
Answer: voltage potential at the earth mat increases due to grounding
17. The objective of earthing or grounding is
a) to provide as low resistance possible to the ground
b) to provide as high resistance possible to the ground
c) to provide flow of positive, negative and zero sequence currents
d) none of the above
Answer: to provide as low resistance possible to the ground
18. Earth wire or ground wire is made of
a) copper
b) aluminium
c) iron
d) galvanized steel
Answer: galvanized steel
19. The advantage of neutral earthing
a) Safety of personnel
b) Reduction of earth fault current
c) Elemination of arcing ground
d) None of the above
Answer: Elemination of arcing ground
20. The advantage of neutral earthing is
a) Freedom from persistent arcing grounds
b) Over voltages due to lightning can be discharged to earth
c) Simplified design earth fault protection
d) All of the above
Answer: All of the above
21. Earthing is necessary to give protection against
a) Danger of electric shock
b) Voltage fluctuation
c) Overloading
d) High temperature of the conductors
Answer: Danger of electric shock
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