Overhead or underground transmission?

Electricity is transmitted along overhead power lines or underground lines. Overhead power lines are a considerably more cost-efficient option for high voltages. Another advantage with them is that faults can be located much more quickly and repaired. However, overhead power lines are much more prone to disruption caused by weather phenomena such as lightning or storms. However, given their ring-operated configuration, customers are unaffected by this.

Underground lines are comparatively more protected against external factors. However, should they require repairs, this is more costly and more time-consuming.

Which technology is used in which case depends upon a number of factors. Underground lines are used more commonly with lower voltages. Underground lines account for about 80 per cent of the low and medium-voltage network. By contrast, only about one per cent of the lines used in the extra-high voltage network are underground.

This is not only due to the substantially higher cost of underground lines, which is scarcely affordable over long transport distances; at extra-high voltage underground lines require additional high-tech equipment.

Protection of the landscape is an ever bigger issue when choosing which type of line to use. There is always a need for compromise between the wishes of the general public, who are upset by the presence of electricity pylons, and commercial and engineering requirements.

Overhead power lines will continue to be indispensable in future for larger volumes of electricity. However, fine distribution to lower voltage levels is increasingly being done underground in Switzerland.