supports of overhead electrical transmission & distribution line

1. Supports Of Overhead
Line
Submitted by:-
Shreyansha Tai Sonwane

2. Index
1) Introduction
2) Line Poles
3) Tower
4) Cross Arms
5) Stay Set
6) Insulators
7) Conductors

3. Introduction
What is an Overhead Line ?
An overhead power line is a
structure used
in electric power transmission
and distribution
to transmit electrical energy
along large

4. Poles
Poles are classified on the basis of material used in
making poles
 Wooden poles
 Concrete poles
a) Reinforced cement concrete poles (RCC)
b) Prestressed cement concrete poles (PCC)
 Steel poles
a) Tubular poles
b) Rail poles
c) RS joist poles
d) H beam poles

5. Wooden Pole
RCC Pole

6. Steel Poles
Cross Section of Rail Pole
Tubular Pole
Rail pole

7. RS Joist
H Beam
Cross section of RS joist
Cross section of H beam

8. Towers
Based on numbers of circuits
carried by a transmission
tower, it can be classified as
 Single circuit tower
 Double circuit tower
 Multi circuit tower.
Single circuit tower

9. Double circuit tower Multi circuit tower

10.  According to the angle of deviation there are four types
of transmission tower
 A – type tower – angle of deviation 0o to 2o
 B – type tower – angle of deviation 2o to 15o
 C – type tower – angle of deviation 15o to 30o
 D – type tower – angle of deviation 30o to 60o
 As per the force applied by the conductor on the cross
arms, the transmission towers can be categorized in
another way
 Tangent suspension tower and it is generally A - type
tower
 Angle tower or tension tower or sometime it is called
section tower
All B, C and D types of transmission towers come under this
category.

11. Angle Tower Tangent Tower

12. Cross Arms
V shaped cross arm Straight cross arm
The purpose of cross arms is
• to provide required space between the conductors
• to provide base for mounting insulators

13. Stay Set
The purpose to use stay set in distribution line is
 To balance the forces of line in different direction.
The main components of stay set are
• Anchor rod
• CI anchor plate
• Stay bow
• Thimbles
• Stay wire
• Stay clamp
• Turn buckle

14. Stay insulator
Stay wire
Thimble

15. Insulators
1) Insulators are mounted on the cross
arms.
2) The purpose of using insulator is to
 Provide insulation between live part
& earth part.
 Provide support to the conductor.

16. Properties of overhead line insulator
 High mechanical strength
 High relative permittivity
 High insulation resistance
 Ability to withstand large temperature
variation

17. Types of insulators
Pin type insulator
Shackle insulator

18. Suspension type insulator Strain type insulator

19. Conductors
The purpose of using Conductor is to
 Transmit the electricity from generation plants to
our houses
Properties of a good conductor
(i) High electrical conductivity.
(ii) High tensile strength in order to withstand
mechanical stresses.
(iii) Low cost so that it can be used for long
distances.
(iv) Low specific gravity so that weight per unit
volume is small.

20. Aluminium conductor steel reinforced
(ACSR)
Cross section of 3 layered ACSR
•Steel strands
•Aluminium strands
•It consists of a pore of galvanized steel strand surrounded by a
no. of aluminium strands.
•The steel pole takes a greater percentage of mechanical stress
while the aluminium carries the bulk current.
•ACSR conductor being of high tensile strength & lighter in
weight produces small sag & therefore can be used for longer
spans.

21. All Aluminum Alloy Conductors
(AAAC)
• In AAAC conductors central strands are made
out of high strength Aluminum-Magnesium-
Silicon alloy.
• These conductors are designed to get better
strength to weight ratio and offers improved
electrical characteristics,
• It has excellent sag-tension characteristics and
superior corrosion resistance when compared
with ACSR.