From the overhead line to the electric socket

Electricity from the power station can reach energy customers in two ways. It can either flow through an overhead power line or it can flow through a cable laid underground. Whether the lines are overhead or underground depends very much on voltage levels. Except in towns and cities, high and extra high voltage power lines cut across the countryside hanging on pylons. Lower voltage power cables usually disappear underground.

Pylon with 220 kV-overhead power line. Photo: Schrader, DUH.

Overhead power line technology

Overhead power line technology has been established and well proven for almost a hundred years. It has many advantages at high voltage levels:

  • large amounts of electricity can be easily transported over long distances
  • bare metal lines are cooled by the air and insulation is only necessary close to the pylons to protect birds
  • electricity can be easily transformed to other voltage levels at substations
  • long durability of the cables and pylons, easy to maintain and repair, easy to detect faults
  • air cooling makes it possible to transport more electricity through overhead power lines than through underground cables, even when the cables are equally thick.

Overhead power line costs

At the high and extra high voltage levels, it is clearly less expensive to build new overhead power lines than it is to lay cables underground. However, apart from costs for the actual construction, other costs and factors must be taken into account. These include operational costs, maintenance, servicing and power losses.

Overhead power lines generally have higher power losses than underground cables. Newly developed particularly thick transmission lines, that can be used in the construction of new high voltage overhead power lines are an exception to this rule because they lose less energy than underground cables. They are, however, susceptible to weather conditions e.g. lightning.

Internationally, as yet, only partial sections of up to 25 kilometers have been constructed at the extra high voltage leveI. It is, therefore, difficult to estimate the extra costs for longer distances.

More information on costs.

Power lines over a field of rapeseed. Photo: Dirk Röttgen, Pixelquelle.de

Nature & the environment

Overhead power lines adversely impact on nature and the environment in several different ways:

  • They alter the overall appearance of the landscape
  • Birds and bats can collide with them or suffer electric shocks. Both are generally fatal.
  • For many years there have been ongoing discussions about if, and to what extent, electromagnetic radiation from the overhead power lines can have an impact on the health of people living nearby.