(a) Yes
(b) No
Answer: B
2. In capacitance grading of cables we use a
______ dielectric.
(a) composite
(b) porous
(c) homogeneous
(d) hygroscopic
Answer: A
3. Pressure cables are generally not used beyond
(a) 11 kV
(b) 33 kV
(c) 66 kV
(d) 132 kV
Answer: C
4. The material for armouring on cable is usually
(a) steel tape
(b) galvanised steel wire
(c) any of the above
(d) none of the above
Answer: C
5. Cables, generally used beyond 66 kV are
(a) oil filled
(b) S.L. type
(c) belted
(d) armoured
Answer: A
6. The relative permittivity of rubber is
(a) between 2 and 3
(b) between 5 and 6
(c) between 8 and 10
(d) between 12 and 14
Answer: A
7. Solid type cables are considered unreliable
beyond 66 kV because
(a) insulation may melt due to higher temperature
(b) skin effect dominates on the conductor
(c) of corona loss between conductor and sheath material
(d) there is a danger of breakdown of insulation due to the presence of voids
Answer: D
8. If the length of a cable is doubled, its
capacitance
(a) becomes one-fourth
(b) becomes one-half
(c) becomes double
(d) remains unchanged
Answer: C
9. In cables the charging current
(a) lags the voltage by 90°
(b) leads the voltage by 90°
(c) lags the voltage by 180°
(d) leads the voltage by 180°
Answer: B
10. A certain cable has an insulation of relative
permittivity 4. If the insulation is replaced by one of relative permittivity
2, the capacitance of the cable will become
(a) one half
(6) double
(c) four times
(d) none of the above
Answer: A
11. If a cable of homogeneous insulation has a
maximum stress of 10 kV/mm, then the dielectric strength of insulation should
be
(a) 5 kV/mm
(b) 10 kV/mm
(a) 15 kV/mm
(d) 30 kV/mm
Answer: B
12. In the cables, sheaths are used to
(a) prevent the moisture from entering the cable
(b) provide enough strength
(e) provide proper insulation
(d) none of the above
Answer: A
13. The intersheaths in the cables are used to
(a) minimize the stress
(b) avoid the requirement of good insulation
(c) provide proper stress distribution
(d) none of the above
Answer: C
14. The electrostatic stress in underground cables
is
(a) same at the conductor and the sheath
(b) minimum at the conductor and maximum at the sheath
(c) maximum at the conductor and minimum at the sheath
(d) zero at the conductor as well as on the sheath
(e) none of the above
Answer: C
15. The breakdown of insulation of the cable can
be avoided economically by the use of
(a) inter-sheaths
(b) insulating materials with different dielectric constants
(c) both (a) and (b)
(d) none of the above
Answer: C
16. The insulation of the cable decreases with
(a) the increase in length of the insulation
(b) the decrease in the length of the insulation
(c) either (a) or (b)
(d) none of the above
Answer: A
17. A cable carrying alternating current has
(a) hysteresis losses only
(b) hysteresis and leakage losses only
(c) hysteresis, leakage and copper losses only
(d) hysteresis, leakage, copper and friction losses
Answer: B
18. In a cable the voltage stress is maximum at
(a) sheath
(6) insulator
(e) surface of the conductor
(d) core of the conductor
Answer: D
19. Capacitance grading of cable implies
(a) use of dielectrics of different permeabilities
(b) grading according to capacitance of cables per km length
(c) cables using single dielectric in different concentrations
(d) capacitance required to be introduced at different lengths to counter the effect of inductance
(e) none of the above
Answer: A
20. Underground cables are laid at sufficient
depth
(a) to minimise temperature stresses
(b) to avoid being unearthed easily due to removal of soil
(c) to minimise the effect of shocks and vibrations due to gassing vehicles, etc.
(d) for all of the above reasons
Answer: C
21. The advantage of cables over overhead
transmission lines is
(a) easy maintenance
(b) low cost
(c) can be used in congested areas
(d) can be used in high voltage circuits
Answer: C
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