Transmission and distribution

1. The minimum clearance between the ground and a 220 kV line is about

4.3 m
5.5 m
7.0 m
10.5 m

Detailed SolutionThe minimum clearance between the ground and a 220 kV line is about

2. The cause of damage to the lead sheath of a cable is

crystallisation of the lead through vibration
chemical action on the lead when buried in the earth
mechanical damage
all of the above

Detailed SolutionThe cause of damage to the lead sheath of a cable is

3. For an overhead line, the surge impedance is taken as

20-30 ohms
70-80 ohms
100-200 ohms
500-1000 ohms

Detailed SolutionFor an overhead line, the surge impedance is taken as

4. The corona is considerably affected by which of the following?

Size of the conductor
Shape of the conductor
Surface condition of the conductor
All of the above

Detailed SolutionThe corona is considerably affected by which of the following?

5. Owing to skin effect

Current flows through the half cross-section of the conductor
Portion of the conductor near the surface carries more current and core of the conductor carries less current
Portion of the conductor near the surface carries less current and core of the conductor carries more current
Any of the above

Detailed SolutionOwing to skin effect

6. As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to earth uses only

31.25 percent of copper
33.3 percent of copper
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
125 percent of copper

Detailed SolutionAs compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to earth uses only

7. Which of the following is the demerit of a ‘constant voltage transmission system’?

Increase of short-circuit current of the system
Availability of steady voltage at all loads at the line terminals
Possibility of better protection for the line due to possible use of higher terminal reactants
Improvement of power factor at times of moderate and heavy loads

Detailed SolutionWhich of the following is the demerit of a ‘constant voltage transmission system’?

8. Which of the following is not a constituent for making porcelain insulators?

Quartz
Kaolin
Felspar
Silica

Detailed SolutionWhich of the following is not a constituent for making porcelain insulators?

9. Which of the following bus-bar schemes has the lowest cost?

Ring bus-bar scheme
Single bus-bar scheme
Breaker and a half scheme
Main and transfer scheme

Detailed SolutionWhich of the following bus-bar schemes has the lowest cost?

10. The square root of the ratio of line impedance and shunt admittance is called the

Surge impedance of the line
Conductance of the line
Regulation of the line
None of the above

Detailed SolutionThe square root of the ratio of line impedance and shunt admittance is called the

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