Electrical Objective Questions:Transmission and Distribution (Set 3)

Electrical Objective Questions With Answers:

1)In overhead lines for transmitting power we generally use:

a) Copper Conductors

b) Aluminum Conductors

c) ACSR conductors

d) Galvanized Steel Conductors

2) ACSR Conductors implies:

a) Aluminum Conductors Steel Reinforced

b) Anodised Core Steel Reinforced

c) All Conductors Surface Reinforced

d) None of These

3) ACSR Conductors are used in overhead transmission lines in place of copper because:

a) Economy factor

b) They are light weight

c) All of these

d) High Tensile Strenght

4) The function of steel wire in the ACSR conductors is to:

a) Compensate for Skin Effect

b) Provide additional mechanical strenght

c) Carry large currents

d) To Reduce Inductance

5) Which material is used for manufacturing of ground wire:

a) Aluminum

b) Steel wire

c) Cast iron

d) Galvanised Steel

6) Effect of Temperature rise in overhead lines is to:

a) Increases the SAG and decreases the Tension of lines

b) Decreases the SAG and Increases the Tension of lines

c) Increase in both SAG and Tension of the lines

d) Decreases in both the SAG and Tension of the lines

7) SAG depends on what factors in transmission lines:

a) Span length

b) tension in the conductors

c) Weight of the conductor per unit lenght

d) All the above

8) In transmission system between two supports, due to SAG the conductors take the shape of:

a) Catenary

b) semi circule

c) Parabola

d) Hyperbola

Answers:

(1) c (2) a (3) c (4) b

(5) d (6) a (7) d (8) a

Explanation for Objective Questions:

1. Answer (c).  ACSR conductors consists of core of galvanised steel strands surrouded by large number of aluminum strands. ACSR is used in long transmission lines because of low cost, reduction in the corona losses any many other factors ACSR conductors are used. 

2. Answer  (a). ACSR conductors means Aluminum Conductors Steel Reinforced. Steel core is surrounded by aluminum strands. Steel core provides greater mechanical strength and aluminum conductors is used to carry bulk amount of current.

3. Answer  (c). ACSR conductors possess high tensile strenght, light weight results in small SAG so large space between towers so cost reduction in number of towers required, larger diameter for same power compared to copper results in reduction in the corona losses.

4. Answer   (b). Galvanised Steel in the ACSR conductors provide better mechanical strenght while the aluminum strands on the outer diameter used to carry the bulk current.

5. Answer   (d). Galvanised Steel wire is cheap in cost and withstand corrosion, so this is used as ground wire.

6. Answer   (a). SAG is termed as the length difference between the line supports and the lowest point of the conductor which causes because of the weight of the conductor. In simple SAG is the bending distance of the conductor. When the temperature increases in summer transmission lines expands results in more bending of the conductor ( SAG increases) and at the same time the tension between the lines decreases

7. Answer  (d). SAG of the conductors depends on the distance between the towers ( Span length), weight of the conductors, tension 0r stress on the conductors because of the towers, and so many factors such as wind, ice loading etc..

8. Answer   (a). Catenary is the curve that forms due to the hanging chains or cables from the supports acted by on its own weight.