Basic Design and Construction aspects of Transmission Lines

1 INTRODUCTION 1.1 What is Transmission line?

This question can simply not be answered by a few words. Each chapter in this lecture notes probably will use to give a proper answer of it.

A transmission line is a device for the transfer of electric energy. It can transfer the energy over long or short distances, and at different voltages. Transfer of electrical energy over very long distances calls for a trunk line with high voltages. The transmission lines of very high voltages, such as; 70 kV, 150 kV, 220 kV, 400 kV, are part of a national grid (GRT in Belgium). To make it easier to understand it can be said that the transmission lines with the higher voltages are the highways in the energy transfer system. In between these highways and the small “paths”, which might call distribution network to drop the voltage line from higher level to lower level, there will be a lot of transmission lines with different voltages.

In the planning and design of transmission line, a number of requirements have to be met. From the electrical point of view, the most important requirement is insulation and safe clearances to earthed parts. These, together with the cross-section of conductors, the spacing between conductors, and the relative location of ground wires with respect to the conductors, influence the design of pylons and foundations.

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