Potential for GW-scale Substations Volume Reduction Moving from HVDC to MVDC using Superconducting Cable Technology

High-temperature superconducting (HTS) demonstrators have been validated to operate with currents up to 10 kA and voltages up to 320 kV, showing potential for implementing GW-scale transmission links at medium-voltage direct current (MVDC). This paper presents a study of the substation design for MVDC GW-scale transmission links, based on HTS cable technology, focusing on the potential benefits and challenges in the implementation. The study considers a target rating of 10 kA / 100 kV for the substation, evaluating three main parallel configurations: MMC with parallel arms, MMCs in parallel and MMC in parallel with LCC. The main parameters under evaluation are the substation’s valve hall size modifications, AC and DC yards requirements and fault handling additional considerations, taking as reference a conventional 500 kV HVDC design with the same power rating. A 3D modelling approach is used to estimate valve hall size for each case, showing potential for a 60% volume reduction compared to the base case due to the reduced insulation distance requirements of the MVDC substation.