This document aims to give an overview of the state of play of extra-high voltage underground connections. It is based on the limited project experience, reports and research available, and on discussions with multidisciplinary experts. Although it is recognised that all projects are specific and require a case-by-case analysis, this is an attempt for the TSO and NGO communities to find common ground.

The project experience with partial undergrounding of 380 kV AC is limited but growing. UC sections have the potential to become an important option in the project development toolbox available to a TSO when planning and executing transmission projects. The collaborative work analysed and formulated recommendations with regard to:

• Impact on the safety and security of the electrical operation
• Legal and regulatory frameworks
• Environmental impacts
• Public Acceptance
• Financial aspects

For more information regarding partial undergrounding, please get in touch with us and contact Cristina Simioli (cristina@renewables-grid.eu).