Mechanical Design of Overhead Lines
CONTENTS
CONTENTS
CHAPTER
&
Mechanical Design of
Overhead Lines
Intr
oduction
Introduction
8.1 Main Components of Overhead Lines
E
8.2 Conductor Materials
8.3 Line Supports
8.4 Insulators
8.5 Types of Insulators
8.6 Potential Distribution over Suspension Insulator String
8.7 String Efficiency
8.8 Methods of Improving String Efficiency
8.9 Important Points
8.10 Corona
8.11 Factors Affecting Corona
8.12 Important Terms
8.13 Advantages and Disadvantages of
Corona
lectric power can be transmitted or dis tributed either by means of underground cables or by overhead lines. The underground* cables are rarely used for power transmission due to two main reasons. Firstly, power is generally transmitted over long distances to load centres. Obviously, the installation costs for underground transmission will be very heavy.
Secondly, electric power has to be transmitted at high voltages for economic reasons. It is very difficult to provide proper insulation† to the cables to withstand such higher pressures. Therefore, as a rule, power trasmission over long distances is carried out by using overhead lines. With the growth in power demand and consequent rise in voltage levels, power transmission by overhead lines has assumed considerable importance.
*
8.14 Methods of Reducing Corona Effect
8.15 Sag in Overhead Lines
8.16 Calculation of Sag
†
8.17 Some Mechanical Principles
159
CONTENTS
CONTENTS
The undergound system is much more expensive than overhead system. Therefore, it has limited use for distribution in congested areas where safety and good appearances are the main considerations.
In overhead lines, bare conductors are used and air acts as the insulation. The necessary insulation between the conductors can be provided by adjusting the spacing between them.
160
Principles of Power System
An overhead line is subjected to uncertain weather conditions and other external interferences.
This calls for the use of proper mechanical factors of saftey in order to
CONTENTS
CHAPTER
&
Mechanical Design of
Overhead Lines
Intr
oduction
Introduction
8.1 Main Components of Overhead Lines
E
8.2 Conductor Materials
8.3 Line Supports
8.4 Insulators
8.5 Types of Insulators
8.6 Potential Distribution over Suspension Insulator String
8.7 String Efficiency
8.8 Methods of Improving String Efficiency
8.9 Important Points
8.10 Corona
8.11 Factors Affecting Corona
8.12 Important Terms
8.13 Advantages and Disadvantages of
Corona
lectric power can be transmitted or dis tributed either by means of underground cables or by overhead lines. The underground* cables are rarely used for power transmission due to two main reasons. Firstly, power is generally transmitted over long distances to load centres. Obviously, the installation costs for underground transmission will be very heavy.
Secondly, electric power has to be transmitted at high voltages for economic reasons. It is very difficult to provide proper insulation† to the cables to withstand such higher pressures. Therefore, as a rule, power trasmission over long distances is carried out by using overhead lines. With the growth in power demand and consequent rise in voltage levels, power transmission by overhead lines has assumed considerable importance.
*
8.14 Methods of Reducing Corona Effect
8.15 Sag in Overhead Lines
8.16 Calculation of Sag
†
8.17 Some Mechanical Principles
159
CONTENTS
CONTENTS
The undergound system is much more expensive than overhead system. Therefore, it has limited use for distribution in congested areas where safety and good appearances are the main considerations.
In overhead lines, bare conductors are used and air acts as the insulation. The necessary insulation between the conductors can be provided by adjusting the spacing between them.
160
Principles of Power System
An overhead line is subjected to uncertain weather conditions and other external interferences.
This calls for the use of proper mechanical factors of saftey in order to