EARTHING or GROUNDING Multiple choice Questions & Answers

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)

Ans: d

 

2. Earth wire or ground wire is made of

a) copper

b) aluminium

c) iron

d) galvanized steel

Ans: d

 

3. Average resistance of human body is

a) 500 ohms

b) 1000 ohms

c) 1500 ohms

d) 2000 ohms

Ans: b

 

4. 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

Ans: c

 

5. 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

Ans: a

 

6. 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)

Ans: d

 

7. 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

Ans: a

 

8. 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

Ans: a

 

9. Moisture content in the soil __ the earth soil resistance

a) increase

b) decrease

c) does not affect

d) none of the above

Ans: b

 

10. Factors on which soil resistance depends

a) depth of the electrode

b) moisture

c) Nacl

d) all the above

Ans: d

 

11. 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

Ans: a