Questions
21
The electrostatic stress in underground cables is
Answer: maximum at the conductor and minimum at the sheath
22
The insulation of the cable decreases with
Answer: the increase in length of the insulation
23
A cable carrying alternating current has
Answer: hysteresis and leakage losses only
24
Capacitance grading of cable implies
Answer: use of dielectrics of different permeabilities
25
In case of three core flexible cable the colour of the neutral is
Answer: blue
26
The advantage of cables over overhead transmission lines is
Answer: can be used in congested areas
27
Cables for 220 kV lines are invariably
Answer: compressed oil or compressed gas insulated
28
Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ?
Answer: Compressed SFe gas
32
The disadvantage with paper as insulating material is
Answer: it is hygroscopic
34
If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be
Answer: 50 cm
35
Underground cables are laid at sufficient depth
Answer: to minimise the effect of shocks and vibrations due to gassing vehicles, etc
38
In the cables, sheaths are used to
Answer: prevent the moisture from entering the cable
39
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
Answer: one half
