Overhead lines: heating and electrodynamic loads

The passage of current through a conductor causes it to heat up; the conductor is also subject to other climatic phenomena such as wind, sunlight and ambient temperature. It is therefore important to be aware of this temperature rise, in order to ensure that the operating temperature of the conductors is compatible with the materials used in their manufacture, and with their deflection above the ground and buildings.

Furthermore, following Laplace's work, we know that the flow of currents in parallel conductors induces electromagnetic forces in these conductors proportional to the product of the currents flowing in the two conductors.

In the event of a short-circuit in a line or substation configuration with flexible conductors, mechanical overvoltages (traction and bending) known as electrodynamic forces are measured at the supports and anchor insulators. Very significant conductor movements are also observed.

As these efforts can be considerable, it is essential to take them into account right from the design stage of a new structure.

These are the two phenomena examined in this article.