Together with a team of experts, Swissgrid has carried out a study on the different types of cable technology in the transmission grid. The solution catalogue – entitled «line construction kit» – includes several innovative designs.
Swissgrid checks the overhead line and underground cable options for every grid project. The decision regarding the planning corridor and the technology (underground cable or overhead line) is prepared in the sectoral plan procedure. The Federal Council then determines both the planning corridor and the technology. As every initial situation is different, various criteria such as spatial development and the environment, as well as technical and economic aspects, are constantly reassessed and weighed up.
There are innovative techniques available today for the construction of underground lines. They increase the leeway for line routing and can also be of interest in terms of costs. In order to evaluate them, Swissgrid has carried out a study with a team of experts with the aim of recording all the types of cable line design relevant to Swiss conditions and examining their suitability and characteristics.
The participating team of experts brings together specialists from the disciplines of construction, electrical engineering and thermal engineering. The study started with a literature review on cable lines in the transmission grid. The team then acquired an overview of the various construction methods. These include trenching via tubes constructed underground, small galleries, mining galleries and tunnels. Part of the study involved technical discussions with manufacturers in order to find out the current state of the art and the costs of different machine types, some of which are new. On this basis, the team developed various types of cable line, examined all the relevant aspects such as heat dissipation, load capacity and magnetic field strengths, and calculated the costs of each design.
The results of the study were used to develop a planning tool for line projects. The line construction kit consists of a catalogue of various designs of underground cable and overhead line. It contains descriptions of the suitability and characteristics of each type of cable technology, as well as an Excel tool for calculating costs. It covers all aspects of line construction, including overhead lines, underground cabling, transition structures and power factor correction.
«The study provides a comprehensive overview of the various designs of underground cable and overhead line and lists their characteristics very precisely, also taking geology into account. For Swissgrid, the line construction kit is an important tool for planning line projects in the transmission grid», according to Sandro Dinser, Head of Requirements & Quality Lines at Swissgrid.