# Mechanical Design of Overhead Lines

## Mechanical Principles in Transmission Lines

Mechanical Principles in Transmission Lines: Mechanical Principles in Transmission Lines design should depend to some extent on the importance of continuity of operation in the line under consideration. In general, the strength of the line should be such as to provide against the worst probable weather conditions. We now discuss some important points in the Mechanical …

## Sag in Overhead Transmission Lines

Sag in Overhead Transmission Lines: While erecting an Sag in Overhead Transmission Lines, it is very important that conductors are under safe tension. If the conductors are too much stretched between supports in a bid to save conductor material, the stress in the conductor may reach unsafe value and in certain cases the conductor may …

## Corona

Corona: When an alternating potential difference is applied across two conductors whose spacing is large as compared to their diameters, there is no apparent change in the condition of atmospheric air surrounding the wires if the applied voltage is low. However, when the applied voltage exceeds a certain value, called critical disruptive voltage, the conductors …

## String Efficiency of Insulator

String Efficiency of Insulator: As stated above, the voltage applied across the string of suspension insulators is not uniformly distributed across various units or discs. The disc nearest to the conductor has much higher potential than the other discs. This unequal potential distribution is undesirable and is usually expressed in terms of String Efficiency of Insulator. …

## Potential Distribution Over Suspension Insulator String

Potential Distribution Over Suspension Insulator String: A string of suspension insulator consists of a number of porcelain discs connected in series through metallic links. Fig. 8.10 (i) shows 3-disc string of suspension insulator. The porcelain portion of each disc is in between two metal links. Therefore, each disc forms a capacitor C as shown in …

## Types of Insulators in Transmission Lines

Types of Insulators in Transmission Lines: The overhead line conductors should be supported on the poles or towers in such a way that currents from conductors do not flow to earth through supports i.e., line conductors must be properly insulated from supports. This is achieved by securing line conductors to supports with the help of …

## Line Support

Line Support: The supporting structures for overhead line conductors are various types of poles and towers called line support. In general, the line supports should have the following properties : High mechanical strength to withstand the weight of conductors and wind loads etc. Light in weight without the loss of mechanical strength. Cheap in cost …

## Conductor Material Used for Transmission and Distribution

Conductor Material Used for Transmission and Distribution: The conductor is one of the important items as most of the capital outlay is invested for it. Therefore, proper choice of material and size of the conductor is of considerable importance. The Commonly used Conductor Material Used for Transmission and Distribution of electric power should have the …