For the success of the energy transition, electrical energy must be transported through Germany over long distances. Currently, this would only be possible with conventional overhead line technology. However, particularly ground-mounted transmission lines would be suitable to minimise environmental interference in the landscape. Gas-insulated direct current lines offer a promising technical approach to this, which, due to their higher transmission capacity compared to conventional cable technology, significantly reduce path widths and thus significantly reduce environmental interventions. In this research project, a 300 m long gas-insulated direct current line is to be built for the first time in a cooperation between industry and public research worldwide and investigated for later use in the electrical grid. Both the construction of the gas-insulated direct current line and the application of test technology to be developed especially for long-term testing are unique worldwide.