1.
Which of the following protects a cable against mechanical injury?
A
Bedding
B
Sheath
C
Armouring
D
None of the above
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Which of the following protects a cable against mechanical injury?
Bedding
Sheath
Armouring
None of the above
Which of the following insulation is used in cables?
Varnished cambric
Rubber
Paper
Any of the above
Underground cables are laid at sufficient depth
to minimise temperature stresses
to avoid being unearthed easily due to removal of soil
to minimise the effect of shocks and vibrations due to gassing vehicles, etc.
for all of the above reasons
The thickness of the layer of insulation on the conductor, in cables, depends upon
reactive power
power factor
voltage
current carrying capacity
The thickness of metallic shielding on cables is usually
0.04 mm
0.2 to 0.4 mm
3 to 5 mm
40 to 60 mm
The surge resistance of cable is
5 ohms
20 ohms
50 ohms
100 ohms
The relative permittivity of rubber is
between 2 and 3
between 5 and 6
between 8 and 10
between 12 and 14
The minimum dielectric stress in a cable is at
armour
bedding
conductor surface
lead sheath
The material for armouring on cable is usually
steel tape
galvanised steel wire
any of the above
none of the above
The intersheaths in the cables are used to
minimize the stress
avoid the requirement of good insulation
provide proper stress distribution
none of the above
The insulation of the cable decreases with
the increase in length of the insulation
the decrease in the length of the insulation
either a or b
none of the above
The insulating material should have
low permittivity
high resistivity
high dielectric strength
all of the above
The insulating material for cables should
be acid proof
be non-inflammable
be non-hygroscopic
have all above properties
The insulating material for a cable should have
low cost
high dielectric strength
high mechanical strength
all of the above
The electrostatic stress in underground cables is
same at the conductor and the sheath
minimum at the conductor and maximum at the sheath
maximum at the conductor and minimum at the sheath
zero at the conductor as well as on the sheath
The disadvantage with paper as insulating material is
it is hygroscopic
it has high capacitance
it is an organic material
none of the above
The current carrying capacity of cables in D.C. is more thanthat in A.C. mainly due to
absence of harmonics
non-existence of any stability limit
smaller dielectric loss
absence of ripples
The breakdown voltage of a cable depends on
presence of moisture
working temperature
time of application of the voltage
all of the above
The breakdown of insulation of the cable can be avoided economically by the use of
inter-sheaths
insulating materials with different dielectric constants
both a and b
none of the above
The bedding on a cable consists of
hessian cloth
jute
any of the above
none of the above