Supports Of Overhead Line

Submitted by:-

Shreyansha Tai Sonwane

Index

1) Introduction2) Line Poles3) Tower 4) Cross Arms5) Stay Set6) Insulators 7) Conductors

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

PolesPoles are classified on the basis of material used in

making poles

Wooden poles

Concrete polesa) Reinforced cement concrete poles (RCC)

b) Prestressed cement concrete poles (PCC)

Steel polesa) Tubular poles

b) Rail poles

c) RS joist poles

d) H beam poles

Wooden Pole

RCC Pole

Steel Poles

Cross Section of Rail Pole

Tubular Pole

Rail pole

RS Joist

H Beam

Cross section of RS joist

Cross section of H beam

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

Double circuit tower Multi circuit tower

According to the angle of deviation there are four typesof 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 crossarms, the transmission towers can be categorized inanother 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 thiscategory.

Angle Tower Tangent Tower

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

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

Stay insulator

Stay wire

Thimble

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.

Properties of overhead line insulator

High mechanical strength

High relative permittivity

High insulation resistance

Ability to withstand large temperature variation

Types of insulators

Pin type insulator

Shackle insulator

Suspension type insulator Strain type insulator

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.

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.

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.