1. Transmission line insulators are made of
(a) glass
(b) porcelain
(c) iron
(d) P.V.C.
Ans: b
2. The material commonly used for sheaths of underground cables is
(a) lead
(b) rubber
(c) copper
(d) iron
Ans: a
3. The minimum clearance between the ground and a 220 kV line is about
(a) 4.3 m
(b) 5.5 m
(c) 7.0 m
(d) 10.5 m
Ans: c
4. The spacing between phase conductors of a 220 kV line is approximately equal to
(a) 2 m
(b) 3.5 m
(c) 6 m
(d) 8.5 m
Ans: c
5. Large industrial consumers are supplied electrical energy at
(a) 400 V
(b) 11 kV
(c) 66 kV
(d) 400 kV
Ans: c
6. In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to
(a) boost the generated voltage
(b) balance loads on both sides of the neutral
(c) make both machine^ run as unloaded motors
(d) equalize voltages on the positive and negative outers
Ans: d
7. In a D.C. 3-wire distributor using balancers and having unequal loads on the two sides
(a) both balancers run as generators
(b) both balancers run as motors
(c) balancer connected to lightly- loaded side runs as a motor
(d) balancer connected to heavily- loaded side runs as a motor
Ans: c
8. Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is
increased 100 percent, saving in copper is
(a) 25 percent
(b) 50 percent
(c) 75 percent
(d) 100 percent
Ans: b
9. A uniformly-loaded D.C. distributor is fed at both ends with equal voltages. As
compared to a similar distributor fed at one end only, the drop at the middle point is
(a) one-fourth
(b) one-third
(c) one-half
(d) twice
(e) none of the above
Ans: a
10. As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum
voltage to earth uses only
(a) 31.25 percent of copper
(b) 33.3 percent of copper
(c) 66.7 percent of copper
(d) 125 percent of copper
Ans: a
11. Which of the following is usually not the generating voltage ?
(a) 6.6 kV
(b) 8.8 kV
(c) 11 kV
(d) 13.2 kV
Ans: b
12. For an overhead line, the surge impedance is taken as
(a) 20-30 ohms
(b) 70—80 ohms
(c) 100—200 ohms
(d) 500—1000 ohms
(e) none of the above
Ans: c
13. The presence of ozone due to corona is harmful because it
(a) reduces power factor
(b) corrodes the material
(c) gives odour
(d) transfer energy to the ground
(e) none of the above
Ans: b
14. A feeder, in a transmission system, feeds power to
(a) distributors
(b) generating stations
(c) service mains
(d) all of the above
Ans: a
15. The power transmitted will be maximum when
(a) corona losses are minimum
(b) reactance is high
(c) sending end voltage is more
(d) receiving end voltage is more
Ans: c
16. A 3-phase 4 wire system is commonly used on
(a) primary transmission
(b) secondary transmission
(c) primary distribution
(d) secondary distribution
Ans: d
17. Which of the following materials is used for overhead transmission lines ?
(a) Steel cored aluminium
(b) Galvanised steel
(c) Cadmium copper
(d) Any of the above
Ans: d
18. Which of the following is not a constituent for making porcelain insulators ?
(a) Quartz
(b) Kaolin
(c) Felspar
(d) Silica
Ans: d
19. There is a greater possibility of occurence of corona during
(a) dry weather
(b) winter
(c) summer heat
(d) humid weather
(e) none of the above
Ans: d
20. Which of the following relays is used on long transmission lines ?
(a) Impedance relay
(b) Mho's relay
(c) Reactance relay
(d) None of the above
Ans: b
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