Overhead lines-the state of the art

In the last 50-60 years there have been many developments in overhead line engineering, most of them resulting from the increase in transmission voltages and from the desire to ensure electrical supplies with a high degree of reliability within acceptable economic and environmental constraints. New mathematical models have been developed for the designs of the many components constituting an overhead line. Probabilistic techniques are now being introduced as a help in decision making. In parallel with the theoretical developments, the contractors have adapted their techniques of installation to the scale and complexities of the constructions; helicopters are providing a convenient `sky-hook´. The stage has been reached, in many instances, where aspects of evaluation of remaining life, diagnosis and maintenance supersede pure design exercises. The author discusses the following aspects of overhead lines: conductors, their properties and characteristics; line mechanical characteristics; line insulators; supports; tower foundations; economic impacts; and construction