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Hybrid overhead power lines

More power without any additional lines

The modernisation of the power grid is yet to be realized in many places. The main reason for that is the lack of acceptance for new power lines. Hybrid overhead lines offer a way out of this dilemma. A conversion allows up to 50 percent more electricity to be transported via the existing overhead lines.

Instead of the usual two alternating current (AC) systems, hybrid overhead lines combine one AC and one direct current (DC) system on the same pylons. This increases the transmission capacity. The lines remain identical in terms of height and width. This means that there is no need to build new lines or disturb the landscape.

As a result of the interference between the AC and DC systems, however, noise and electrical fields may occur, depending on weather conditions, dirt on the conductors and the distance between the DC and AC conductors.

Hybrid power lines in the field test (in German)
Hybrid power lines in the field test (in German)

A research group from ETH Zurich investigates the optimum layout of the system in the context of the National Research Programme «Energy Turnaround» (NRP 70). The researchers, headed by project leader Christian Franck, Professor at the Institute for Power Systems and High Voltage Technology, test voltages and pylon geometry on lines in the laboratory and under real-life outdoor conditions. The aim is to develop lines with high transmission capacities and minimal negative effects on the environment.

In addition to the development of the new technology, the chances and the procedure to ensure that it will benefit from the necessary social acceptance, were also investigated. This was undertaken in collaboration with the Institute of Political Science at the University of Bern. Isabelle Stadelmann-Steffen, Professor at the University of Bern, is investigating the social acceptance of renewable energies in the National Research Programme «Managing Energy Consumption» (NRP 71). The survey of around 1,300 people regarding their attitude to hybrid overhead lines produced three key findings:

  1. There is a need for information about the new technology. The public should be included in the project as early as possible and have the opportunity to contribute their concerns and misgivings.
  2. Alternatives must be discussed. The study shows that the conversion of an existing line into a hybrid line is more popular than a new conventional line.
  3. The more possible negative effects of a technology can be reduced, the greater will be its acceptance.

Discuss the project with experts from ETH Zurich and Swissgrid. Visit us at Powertage (hall 6, stand J09) from 5 to 7 June 2018 in the «Messe Zürich».


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