Completed project: Hybrid overhead power lines for Switzerland

The image shows the so-called corona effect of a high-voltage power line in the laboratory
In the high-voltage laboratory of the ETH Zurich, the researchers were able to accurately examine the behaviour of hybrid power lines under various conditions, including corona effects.

Combined AC/DC power lines can considerably increase the capacity of the transmission grid. Environmental impacts can be reduced to an acceptable level.

The required grid reinforcement is therefore a crucial factor for the success of the Energy Strategy 2050. However, acceptance for new transmission lines is very low, hence, delaying the reinforcements and possibly leading to congestion.

Through a hybrid AC/DC conversion of existing multi-circuit AC overhead lines, with AC and DC on the same tower, the transmission capacity can be significantly increased without the need for new corridors. In this way, delays in construction can be avoided thanks to higher acceptance.

The implementation of a hybrid line in Switzerland can contribute to higher grid availability and make it possible to use cheaper and more remote energy sources. The project team of Prof. Christian M. Franck from the Department for High-Voltage Technology at the ETH Zurich demonstrated that a hybrid line conversion is generally more acceptable than the construction of a new transmission line.

Thanks to the measurements and simulations conducted as part of the NRP 70 research project “Hybrid overhead power lines for Switzerland”, these effects can be predicted more accurately and reduced to an acceptable minimum.

Two possible North-South corridors have been identified as potential routes, and the conversion was shown to be feasible for a typical Swiss tower, although the existing small bundles pose a considerable challenge as regards the reduction of corona effects..

Further information on this content


Prof. Christian M. Franck Departement für Hochspannungstechnologie D-ITET
ETH Zurich
Physikstrasse 3
ETL - H 28
8092 Zürich +41 44 632 47 62