Underground Cable MCQ

1. Dielectric strength of rubber is around

1. 5 kV/mm
2. 15 kV/mm
3. 30 kV/mm
4. 200 kV/mm

2. In single core cables armouring is not done to

1. avoid excessive sheath losses
2. make it flexible
3. either of the above
4. none of the above

3. The minimum dielectric stress in a cable is at

1. armour
2. bedding
3. conductor surface
4. lead sheath

4. Conduit pipes are normally used to protect _____ cables.

1. unsheathed cables
2. armoured
3. PVC sheathed cables
4. all of the above

5. _______ cables are used for 132 kV lines.

1. High tension
2. Super tension
3. Extra high tension
4. Extra super voltage

6. In case of three core flexible cable, the colour of the neutral is

1. blue
2. black
3. brown
4. none of the above

7. The current carrying capacity of cables in D.C. is more than that in A.C. mainly due to

1. absence of harmonics
2. non-existence of any stability limit
3. smaller dielectric loss
4. absence of ripples

8. In a cable immediately above metallic sheath, _____ is provided.

1. earthing connection
2. bedding
3. armouring
4. none of the above

9. The insulating material for cables should

1. be acid proof
2. be non-inflammable
3. be non-hygroscopic
4. have all above properties

10. The bedding on a cable consists of

1. hessian cloth
2. jute
3. any of the above
4. none of the above

11. The thickness of the layer of insulation on the conductor, in cables, depends upon

1. reactive power
2. power factor
3. voltage
4. current carrying capacity

12. Empire tape is

1. varnished cambric
2. vulcanised rubber
3. impregnated paper
4. none of the above

13. Which of the following insulation is used in cables?

1. Varnished cambric
2. Rubber
3. Paper
4. Any of the above

14. Which of the following protects a cable against mechanical injury?

1. Bedding
2. Sheath
3. Armouring
4. None of the above

15. The insulating material for a cable should have

1. low cost
2. high dielectric strength
3. high mechanical strength
4. all of the above

16. _____ is done just above the bedding’s surface.

1. Metallic sheathing
2. Serving
3. Insulation
4. Armouring

17. In comparison to overhead transmission, in underground systems

1. Voltage loss is less
2. Fault correction is easier
3. Value of charged current is less
4. Initial cost of the system is low

18. Which of the following may not be the possible reason for open circuit fault in the cable?

1. Due to the rupture of electric insulation
2. Due to excessive pressure
3. Due to the breaking of core of cable
4. Due to swift turn

19. The effect of bonding the cables is to

1. Increase effective resistance and inductance
2. Increase effective resistance but reduce inductance
3. Decrease effective resistance and inductance
4. Decrease effective resistance but increase inductance

20. The insulation resistance of a cable of length 10 km is 1 Mega ohm. Its resistance for 50 km length will be

1. 1 Mega ohm
2. 5 Mega ohm
3. 0.2 Mega ohm
4. 50 Mega ohm